Tijdschrift van het Nederlands Radiogenootschap

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1 Tijdschrift van het Nederlands Radiogenootschap DEEL 20 No. 5 SEPTEMBER 1955 Shore^based radio aids to navigation on centimetric wavelength by J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm *) SUMMARY The problem of shore-based radar as a navigational aid for shipping is discussed from the system engineering point of view. A short review of the work carried out in the Netherlands, Belgium and W estern Germany is given. R ad io aid s to n avigation have become more effective a s the p ractical application of very high frequencies and pulse techniques w ere introduced. N ew n avigational aid s w ere born and in the p a st decade the m ariner h as been provided with in stru m ents he never dream t of before. F o g and b ad visibility still rem ain d read fu l enem ies, but the pen etration of fog achieved by the use o f n arrow beam s of electrom agnetic w av es o f ap p ro p riate w avelength and pulses of fraction s of m icroseconds have given to the m ariner the tools to avoid collisions a t se a and to m ake lan d fall easier. A lthough m arine r a d a r is now w idely used, the situation in thick w eath er a t estu aries and en tran ces to inland p o rts is still the sam e a s b e fo r e : a g re a t num ber of ships is anchoring and only a few go-getters d are to steam up, relying on their marine ra d a r. M ultiple echos caused by n earby ships, interference from other m arine r a d a r sets, shadow a re a s in river-bends and sidelobe effects m ay how ever cause ex tra d an ger b y m isinterpretation of the r a d a r inform ation. In w aterw ay s, full of bends and lined w ith buildings along the ban ks, the picture on the m arine r a d a r screen does not extend around the follow ing bend. N o m arine r a d a r h as y e t *) Netherlands R adar Research Establishment, Noordwijk-The Netherlands.

2 272 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm be en devised, sim ilar to the machine-gun recen tly announced, which is claim ed to be able to fire around corners. H ere the use o f sh ore-based r a d a r in stallations can definitely bring a solution, providing th at g reat care is given to the siting, the technical specifications and the operational procedure of such system s, in other w o r d s : to the system engineering. The In tern ation al M eetin g on R ad io A id s to N av igatio n (IM R A M -co n feren ce), held in London in 1946, m ade the first recom m endations for the use of sh ore-based r a d a r and r a d a r beacons. The form ulation of these recom m endations w ith regard to this special application of r a d a r w as rem ark ably to the point. I w ould like to quote it b rie fly : The object of the facilities a t p resen t provided by p ort and h arbour auth orities is to affo rd a ship a safe and easy entrance or exit and a safe anchorage or berth under all conditions of w eather. It is obvious th at r a d a r can supplem ent these facilities very v alu ab ly by providing v irtu ally in stan tan eous inform ation of movem ents in the p o rt a r e a. I f the location of a sh ore-b ased ra d a rsta tio n is chosen ju d i ciously and full ad v an tage is taken of all the refinem ents, offered b y m odern r a d a r technique, it is p ossib le to achieve a ra d a r picture, which is so sh arp and distinct th at the resu lts are infinitely superior to those obtained by a r a d a r in stallation on b o ard of a ship, proceeding in the sam e area. The low countries a t the d eltas of Rhine, M a a s and Sch eld t with the m ajor p o rts A m sterdam, R o tterd am and A ntw erp which are connected with the N orth S e a by long inland w a te r w ay s and w here navigation is frequen tly m enaced by fog and b ad visibility, form an ideal p ractisin g ground for this new technique of sh ore-based n avigational aids. The m em bers of the conference *) have alre ad y been provided w ith a rep o rt of C ap tain H. Tichelm an on the first shoreb ased ra d a rsta tio n in stalled on the E u ropean continent a t Ym uiden, which w as put into operation in N ovem ber A n other rep o rt w as given by the N eth erlan d s R a d a r R esearch E s t a blishm ent on the developm ent of w h at w ell m ay be considered a t present a s the m ost extensive system of sh ore-based rad arstatio n s in the w o rld : the system fo r the N e w -W a te rw a y and *) International Conference on Lighthouses and other aids to Naviga tion, Scheveningen 1955.

3 Shore-based radio aids to navigation on centimetric wavelength 273 4> ÖJ 4 > -C.0 C 4) > JC X Ü 4 > u o jc cu ct o B c/3 <D _c c o "Ö 42 bfl ctj Uh 72 c *4) E4 ) - C u 72 u oj "d Oj u p ' Oj c 4 ) Ë _D- "3 cr 4 ) u «Ö "d ctf 72 4) *d 4 > 72 Cö -O 4) U o JC 72 fls J-l c 4) t- 42 CU X

4 274 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm R ail a r picture taken at Cuxliaven dun iiii W 1n te i' 1953 when the Elbe was covered with drill ice the port ol R o tte rd am, which is now under con struction and will be ready next year. ««It is hoped th a t these tw o re p o rts will su pply to the conference sufficient technical and operational inform ation on these system s. The picture how ever would not be com plete if the conference w ere not informed on the further developm ents in this field. It is now p o ssib le to give more inform ation on recent e x p e rim ents and survey w ork, carried out m connection with the siting of sh ore-based ra d a rsta tio n s at the Scheldt estu ary on D utch and Belgian territo ry and in W estern -G erm an v at the E lbe estu arv. «T hese experim ents and the survey w ork are being carried out bv the N eth erlan d s R a d a r R esearch E stablish m en t on the request of the B elgian M in istry of T ransport and the W est- G erm an B undesverkehrsm inisterium. The N eth erlan d s R a d a r R esearch E stablish m en t had placed at the d isp o sal of the Bundesverkehrsm inisterium ra d a r experts, trained personnel and experim ental sh ore-based r a d a r equipment. Tw o experim ental shore-based ra d a rsta tio n s have been

5 Shore-based radio aids to navigation on centimetric wavelength 275 built under this scheme in C uxhaven and in B runsblittelkoog and have been in operation w ith good resu lts fo r more than a y e a r under all conditions of w eath er, including a period in which the E lb e w as p artly covered by ice, which sw ep t the n avigational buoys aw ay. D urin g this experim ental period the tw o statio n s have proved to be a m ost useful aid to navigation. N um erous rep o rts of G erm an pilots, who equipped w ith p o rtab le V.H.F. tran sceiv ers w ere takin g an active p art in these trials, have been a m ost valu able contribution to d raw up recom m endations fo r the operational procedure of the final system. The N eth erlan d s R a d a r R esearch E stab lish m en t h as recen tly com pleted its studies on the E lb e-riv er r a d a r scheme and has now subm itted to the W est-g erm an M in ister of T ran sp o rt the final plans lo r a sh ore-based r a d a r system which w ill cover the whole of the E lb e estu ary from the L igh tv essel E L B E I to B runsblittelkoog a t the entrance of the N o rd -O stse e K a n a l (K iel canal). In this plan it is recom m ended to build four sh ore-b ased ra d a rsta tio n s w ith advan ced technical specifications, each using 60 k W p eak pow er m agnetrons w ith v ariab le frequency in the 3cm- or X -b an d. The horizontal beam o f the r a d a r antennae w ill h ave to be in the o rd e r o f 0.6, p u lse-len gth 0.08 m icrosecond. The method of presen tation on the r a d a r screen, which has a recom m ended diam eter of 15", is of a special ch aracter. A p air of w andering electronic cursor lines w ill m ake it possible to provide to all ships under the coverage of the r a d a r system accu rate inform ation in range and bearing relativ e to any desired position ash ore or a t sea within the range of the rad arstatio n. In the sam e w ay a num ber of w andering electronic lines can be sw itched in a t w ill or w ill ap p e a r au tom atically on the screen to m ark the n avigational channel or an y desired line of approach or leading-lines. This method of presen tation is known a s R a p lo t. A t the Sch eld t estu ary a v a st program is being carried out b y the N eth erlan d s R a d a r R esearch E stab lish m en t on the req u est of the B elgian M in ister of T ran sp o rt and w ith the full co-operation of the N eth erlan d s auth orities. A mobile su r vey is carried out along the shores o f the Sch eld t from A n t w erp to the mouth ol the river and on the coastline from O sten d e to W e st-k a p e lle.

6 276 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm The aim of this survey w ith mobile r a d a r equipm ent is to allo cate the p roper sites fo r sh ore-based ra d a rsta tio n s in this a re a and to determ ine their range and technical specifications. A fte r com pletion of the survey tw o experim ental sh ore-based ra d a rsta tio n s w ill be built a t ap p ro p riate sites a t the Sch eldt e stu ary to gain operational experience w ith the la te st technical develop m en ts in th is field. F o r those, who are in close touch w ith these problem s, it w ill be obvious th at the designer w ill not only have to a d a p t the system to the specific geographical situation of the a re a concerned, but th at he m ust also b ase his design on the specific operational requirem ents of navigation in pilotage w aters. The system engineering of a sh ore-based r a d a r system is a com plex ta sk of balancing out a g re a t num ber of im ponderables of a physical, nautical, geographical and econom ical ch aracter, thereby con stan tly keeping in mind the p resen t state of developm ent of the r a d a r technique. In m ost case s a survey with mobile r a d a r equipm ent or a t le a st a tem porary in stallation of experim ental r a d a r equipm ent a t su itable sites is essen tial. The mobile survey m ust be preceded by a carefu l stu d y of the prevailing practice, the pilotage s y stem, the to p ograp h ical d a ta and the local geographical situation. The r a d a r equipm ent fo r experim ental use or mobile survey w ork in connection w ith sh ore-based r a d a r system engineering m ust have a high degree of perform ance in ran ge and bearin g and m ust be provided w ith facilities to off-centre the picture and p referab ly have m eans to read accu rately distance and bearing, not only from the centre of the screen, but also from any off-centre position to any desired position within the range of the equipm ent. F u ll facilities fo r taking photograph s of the r a d a r picture are needed. O b se rv atio n s of all seam ark s and other points o f im portance to navigation should constan tly be m ade and checked w ith the r a d a r ph otograph s to ensure th at all the n av igatio n al m arks, n ecessary to provide in stan tan eous n avigational inform ation, can be seen under all circum stances. M ean s to erect the scanner quickly on 30 to 40 feet above ground level are in d ispen sab le; a p ow er generating p lan t should be provided to ensure com plete freedom of choice for the tem p o rary sitings. A rm ed w ith all these facilities, the mobile survey can sta r t w ith the aim to allocate the p ro p er sites of the minimum numb er of statio n s, n ecessary to give com plete r a d a r coverage in

7 Shore-based radio aids to navigation on centimetric wavelength 277 Sh ore based radar equipment on mobile survey for the Schtddt estuary radar scheme i! I

8 278 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohin th e area concerned. The technical specifications of each of th ese stations are meanwhile being considered and gradually take a definite shape. It will be obvious th at advan ced technical specifications n ecessitate further research and developm ent w ork to solve som e specific problem s. The identification of ships, coming under the coverage ol a shore-based rad arstatio n, has hitherto not been solved in a satisfacto ry w av. A new method is now being investigated, w hereby unam biguous identification can be obtained wi th a minimum ol equipm ent to be taken on board by the pilot. T ransm ission of the ra d a r pictures to an operational h eadq u a rte r d o es no more con stitu te a technical problem and t n Radar picture with two leading lines, taken at W aa rde d u ring the mobile survey for the Scheldt estuary radar scheme

9 Shore-based radio aids to navigation on centimetric wavelength 279 m ay in some case s lead to a more elab o rate and sm oothrunning system, which m ay help to economise the personnel problem. It rem ains questionable w hether the transm ission of r a d a r pictures from shore to ship will p ay itse lf and will be suitable fo r general adoption. Th e use of circular p o larisation m ay reduce undesired re flections from rain clouds. A higher degree of definition m ay still be w an ted fo r the last stage ol berthing a ship in the inner p o rt a re a and m ay w ell lead to the use of m illim etric w av es in the 8mm- or Q - band for these special circum stances. In m aking lan d fall another group of rad io aid s to navigation, using m icrow aves, m ay w ell be suitable to support the lan d fall procedure and to im prove the use of m arine r a d a r for n av igation in co a stal w aters. Lighthouses, ligh tvessels and lightbuoys, when transm itting electrom agnetic w av es in addition to the lightflashes, which are ab so rb ed in thick w eath er, m ay help to identify these n av igational m arks in spite of fog. In the N eth erlan d s both R am ark and R acon are being d e veloped for this purpose by the N eth erlan d s R a d a r R esearch E stab lish m en t and a rep o rt on a new ly developed R am ark insta lla tio n w ill be given to the con ference, fo llo w ed by a d e m o n stratio n on June the 7th.

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11 September Deel 20 - No A ramark beacon for use with marine radars by J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm *) SUMMARY In this paper a broad band high power 3 cm-ramark equipment is described with a range of max. 30 miles. Propagation difficulties have been largely overcome by a diversity system of transmitting aerials. Elimination of the ramark signal from the ship s P.P.I. is made possible by use of the F.T.C. circuit in the marine radar. The specifications of this ramark and results of trials are discussed. 1. Introduction A v a st am ount of experience is gained by the u sers of marine ra d a rs as installed n o w ad ay s on b o ard thousands of m erchant ships. It is generally accepted th at some auxiliary aid w ould be useful for the purpose of identification of insufficiently ch aracteristic coastlin es and of ligh tvessels. This n avigation al aid should be used during the la st phase in making lan d fall and for co a stal navigation, its useful range being from 3 30 miles off shore In view of this problem tw o types of experim ental b e a cons have been produced, which are known as ram ark s and racons, the form er giving bearin g inform ation only, the latte r range inform ation as w ell. W hile the A m erican rad ar-b eaco n s are w orking in a special beacon band ( M c/s) outside the band allo cated for marine rad a r, U.K. developm ent w as aim ing a t a beacon, covering the whole m ercantile marine rad arb an d, elim inating the need for the provision of a sep arate R.F. head, tuned to the beacon frequency, in the marine ra d a r equipm ent. 2. E x istin g radarbcacons 2.1. U p till now rad arb e aco n s have been establish ed on an experim ental b asis only. The beaconband types can be used only in conjunction with radarequipm en t provided with specially built in R.F. heads fo r the ban d M c/s. It is clear th at the application of this type of beacon is therefore limited and in view of the fact th at many thousands of modern ra d a rs, in stalled on b oard of m erchant ships, have not this facility and cannot even be modified in this respect, operational use of these types of beacon s seem s very rem ote. *) Netherlands Radar Research Establishment, Noordwijk, The Netherlands.

12 282 }. M. F. A. van Dijk, N. Schimmel and E. Goldbohm 2.2. The main developm ent of rad a rb a n d beacon s w as done up till recently in the U.K. A R acon type beacon w as developed by A.S.R.E.]) a fte r earlier w ork on a R am ark, operating in th e m arine rad arb an d, and tem porarily in stalled a t S t. C a therine's L ig h th o u se12 3). It is outside the scope o f this article to enlarge upon the R acon type of beacons. The B ritish R am ark m entioned above used norm al types of klystron s, six of which w ere nee ded for com plete coverage of the m arine r a d a r band. The pow er output how ever w as insufficient fo r reliable long range perform ance and a very annoying shortcom ing of these beacon s is the presence of zones of minimum sign al caused by interference betw een the direct rad iation and the one reflected by the surface of the s e a 8). From an earlier p ap er of D. G. K iely and W. R. C a r t e r 4 *) it w as alread y known th at very deep fadin g w as m easured in the propagation of 3-cm w av es over a seap ath during experiments carried out betw een July 1950 and Jan u ary 1951 betw een S elsey B ill and E a stn y F o rt E a st, n ear Portsm outh harbour A study of the resu lts of the w ork carried out in developing b ro ad b an d ram ark beacons show s clearly th at mainly three facto rs w ere responsible for the fa c t th at a generally accep tab le solution fo r a ram ark could not be reached. These fa cto rs w e r e : The non existence of an (electrically) tunable b ro ad band oscillator w ith sufficient pow er output, of sim ple design and w ith a minimum o f circu it requ irem en ts The existence of zones of minimum signal, m aking on-off coding am biguous and confining the operational use seriously The alm ost com plete m asking of the r a d a r picture a t sh ort ran ges (see e.g. fig. 1 of A) ). 1) A Racon beacon for reception by Civil Marine Radars by C. Randall- Cook (A.S.R.E.). Journal of the Institute of Navigation, Vol. VII, No. 2, April ) A.S.R.E. Technical Note TX/ "Installation of Experimental Ra- marks in Lighthouses by N. Bell. 3 ),,The use of Radar at Sea. The Institute of Navigation, London, Hollis & Carter 1952, pp. 165 s.s. and fig ) An Experimental Study of fading in propagation at 3-cm wavelength over a sea path, D. G. Kiely, M.Sc., and W. A. Carter, B.Sc., Proceedings I.E.E., London, Vol. 99, Part III, No. 58, March 1952.

13 A ramark beacon for use with marine radars Development in the N eth erlan ds 3.1. In 1953 the developm ent of a high p ow er b ro ad ban d r a m ark w as sta rte d bv the N ed erlan d sch R a d a r P ro efstation (N eth erlan d s R a d a r R esearch E stab lish m en t) a t N oordw ijk. A t th at time a special tube becam e av ailab le, produced by Philips, Eindhoven, known a s the m ultireflex klystron. This tube p ro duces 10 W a t t s of continuous R.F.p o w e r a t 3-cm and can be tuned over a band of 180 M c/s a t the rate o f e.g. 50 tim es per second. A p a rt from this sim ultaneous m odulation w ith fre quencies of the ord er of kilocycles is p ossible. D evelopm ent w as b ased upon the follow ing con siderations: Z o n es o f minimum or no sig n al should be elim in ated U nam biguous on-off coding should be provided R eduction of the m asking of the r a d a r picture a t short ran ges should be pursued These considerations m ay be enlarged upon in the follow ing p aragrap h s Elim ination of zones of minimum signal. This effect is caused by the interference of the direct rad iation and the one reflected by some plane e.g. the su rface of the sea. T h eo retically it is p o ssib le to elim inate this effect by using the principle of diversity transm ission. F o r the purpose of testin g out this system under operational conditions, a ram ark tran sm itter (fig. 6), which w ill be described in some d etail in 4.3, w as tem porarily in stalled in the sem aphore a t IJm uiden. The output could be sw itched by m eans of a w aveguidesw itch to one of tw o aerials of a b ro ad band slo tted w aveguide type (see 4.2 and fig. 8) the lo w est one being 54 ft above mean w aterlevel, the highest one being 21 ft higher. The ram ark sign al w as observed on a D ecca M arin e R a d a r type 12, in stalled on b o ard the buoyage ten der Z aan d a m which v essel w a s m ade av ailab le for the experim ents through the co-operation of the D irecto r of P ilo t age of the d istrict. D urin g trials the effect of minimum signal zones could be observed and it w as alw ay s possib le to receive the ram ark sign al again b y sw itching over to the other aerial. A solution for operational use is the follow ing. It is a go od practice to duplicate shore b ased electronic n avigational aid s. This ap p lies as w ell to r a m a r k s; therefore in practice there w ill be tw o tran sm itters av ailab le an y w a y as p a rt of the beacon equip

14 284 J. ML F. A. van Dijk, N. Schimmel and E. Goldbohm ment. The b e st solution, and an economic one a t the sam e time, w ill be to have tw o ram ark tran sm itters, each connected with its own aerial and to choose the aerial heights such, th at the w an ted effect w ill be reached for varying heights of ships ra d a r aerials as met in ships in stallations. In case of breakdow n of one of the tran sm itters, there w ill still be a ram ark signal, be it w ith the lim itations of the presence o f a minimum signal zone, which is alw ay s b etter than com plete interruption of the service. A lthough there has not y et been sufficient time av ailab le to in vestigate the effect of the diversity ae rial system over longer periods in resp ect to the big fluctuations of sign al strength over a se a p ath as experienced by single aerial system s (4) it is very p robab le th at this problem is solved a t the sam e time, reducing the w an ted R.F. pow er to som ething of the order of 10 W a tts B ecau se of the elim ination of minimum signal zones, onoff coding becom es a p ractical proposition. O u r belief is, th at com paritively long off-periods, divided by sh ort on-periods w ill be ad equate fo r fulfilling the ta sk of a ram ark, e.g. 50 seconds off (or even longer) and 10 seconds on. In this case on the av erage the ram ark signal w ill be d e picted tw o to three tim es consecutively during each period of 1 minute w hich is sufficient to ta k e a b earin g. This type of coding is to be p referred above the one using various H.F. m odulation frequencies, becau se the shape o f the signal (d ots or d ash es) depends to a high extent on the range scale used on the m arine rad ar. A p a rt from the p o ssib ility to overcom e m asking of the ra d a r picture a t sh ort ran ges by application of a su itable H.F. modulation frequency in conjunction w ith the F.T.C.-circu it of a m arine ra d a r, an on-off coding a s outlined above leaves the r a d a r picture under the w o rst circum stances unaffected during a t le a st 80 /0 of the time The provision of F.T.C. circuits in marine ra d a rs which can be sw itched on to overcom e the effect of serious rain clutter h as become more and more a stan d a rd featu re of modern ship's rad a rs. It m ay be sta te d th at the m odification to provide existing ra d a rs which have not this featu re incorporated with such an an ti-rain clu tte r device is on ly a m inor one. A n in v es

15 A ramark beacon for use with marine radars 285 tigation into the time con stan ts of F.T.C. circuits in presen t d a y sh ip's ra d a rs has shown th at they differ rath er w idely. T h eoretical considerations follow ed up b y some experim ents have show n th at an H.F. m odulation of 5 10 kc/s seem s a good com prom ise to ensure the elim ination of the ram ark signal from the P P I picture by sw itching on the F.T.C.-circu it. In the prototype equipm ent, described in some d etail in 4.3, a w ide range of m odulating frequencies is av ailab le. The siting of a ram ark is very im portant in view of the eventual m asking of ship's r a d a r pictures. W e are of the opinion th at the main purpose of a ram ark is the provision of m eans to the u ser of marine r a d a r to identify insufficiently ch aracteristic targ e ts along a coastline to prom ote the possibility of establish in g his position with the aid of his ra d a r. In this resp ect the beacon can be situated on such a site th at shipping w ill never come closer than sa y 3 miles from the beacon, elim inating in this w ay the m asking and cluttering up of the picture through side- lobe effects to a g reat extent. W e are aw are of the fact th at this policy could not a lw a y s be follow ed but in the m ajority of case s ad v an tage could be taken of this method for a great deal. In case of ram ark s installed on ligh tvessels the situation is different, ships p assin g them gen erally rath er close. A p a rt from the possib ility of using the F.T.C. circuit an intelligently chosen on-off coding might p ro ve sufficient under th ese circu m stan ces B a se d upon these con siderations an experim ental ram ark w as built (fig. 6) and w as used during some sea-trials with the buoyage tender Z aan d am '' mentioned above. A t the time the photograph s, which are reproduced in this rep o rt w ere taken, the low est H.F. m odulation w as 75 kc/s, which w as not sufficient to ensure com plete elim ination of the ram ark signal, as show n on the photograph s (fig. 2). It m ay be state d th at the perform ance of a ram ark beacon from the u sers' point of view is governed to a ver3r g re a t extent by the perform ance of the m arine rad a r. The an gu lar w idth of the ram ark signal is entirely dependent on the rad iatio n p attern of the r a d a r aerial, its sidelobe level being of param ount im portance a t sh orter ran ges. It should be rem em bered th at the sidelobes on the ram ark signal as depicted on the P.P.I. have only h alf the atten uation expressed in db w ith resp ect to the main beam in com parison w ith the sidelobes visible of ra d a rta rg e ts. A p a rt from the m arine ra d a r as such, the siting on board

16 286 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm Fig. 1. Range Scale P.P.I.: 3 N.M. Beacon Range: 2.3 N.M. Beacon modulation frequency: 75 kc/s without Fast Time Constant. Bad sidelobes visible over 270. Fig. 2. Range Scale P.P.I.: 3 N.M. Beacon Range : 2.1 N.M. Beacon modulation frequency: 75 kc/s W ith F.T.C. Beacon signal considerably reduced. Picture unfortunately disturbed by yawing of ship. Fig. 3. Range Scale P.P.I.; 25 N.M. Beacon Range : 15 N.M. Beacon modulation frequency: 300 kc/s. W ithout F.T.C. Bad yawing of the ship visible on ramark and 3 coastline echo signals. Fig. 4. Range Scale P.P.I. : 10 N.M. Range M arker through beacon: 7,5 N.M. Beacon modulation frequency: 75 kc/s. W ithout F.T.C. Picture di-sturbed by yawing. Fig. 5. Range Scale P.P.I. : 25 N.M. Range M arker : 3 N.M. Beacon Range : 21 N.M. Beacon modulation frequency : 300 kc/s. W ithout F.T.C. Yaw ing of ship. Fig. 6. Complete Ramark equipment in standard 19 rack as used during the experiments. Beacon aerial type slotted waveguide is also shown. Fig. 7. Close up of Philips multireflex klystron with magnet and w aveguide. Fig. 8. Semaphore at IJmuiden. Both beacon aerials can be distinguished on the long vertical waveguiderun in the centre of the picture.

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19 A ramark beacon for use with marine radars 287 the ship is of g reat influence. The p ossibility to receive indirect rad iation, reflected from p a rts of the sh ip's su perstru ctu re spoils the chance to receive a clean ram ark sign al and ra d a ra e ria ls in stalled close to a sh ip's m ast or other steel stru ctu res m ay suffer seriously in sidelobe perform ance a p a rt from the fact th at unw anted large d ead an gles are p resen t a t the sam e time. U n fortu n ately the ae rial siting on b o ard the buoyage tender Z aan d a m " is in this resp ect fa r from ideal, although the sp e cial ta sk this v essel h as to fulfil, m ade another siting virtually im possible. The aerial w as in stalled on a console in fron t of the very heavy bipod m a st; a t the time of w riting this rep ort it w as tried to im prove conditions b y the in stallation of an oblique deflector p late betw een the aerial and this m ast. D urin g trials ran ges o f 27 n.miles w ere achieved, which w as beyond the ra d a r horizon under the prevailing circum stances. 4. D escription o f the ram ark-eqnipm ent 4.1. The ram ark equipm ent consists of tw o main p a r ts: The aeria l system The ram ark tran sm itter. B oth p a rts w ill be described in some detail The aerial p ro p er of the ram ark consists of a b ro ad b an d non reson an t slo tted w aveguide, which rad ia te s a n arrow beam ap p rox, norm al to the a r r a y in the v ertical plane and a w ide beam (g reate r than 180 ) in the horizontal plane giving coverage along e.g. a straigh t coastline. In ord er to obtain optimum gain o f the aerial system, the length of the a rra y h as been determ ined consistent w ith such a w idth of the v ertical beam, th at the variation of sign al strength on the horizon does not exceed approx. 3 db during a sw eeping cycle of the oscillator. This variation origin ates from the fact, th at the direction of m ax. radiation in the v ertical plane v aries w ith the frequency o f the oscillator. This is a ch aracteristic inherent to non re so nant aeria l a rray s. W h en the o scillato r sw eeps through the marine r a d a r band, the vertical beam sw eeps through 1,5 degrees. The aerial m entioned above h as been chosen to give a v ertical beam w idth of 1,3 degrees. T rials have shown, th at the system h as am ple gain and th at

20 288 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm indeed a reduction of the gain w ith a fa cto r of 3 or 4 w ould leave an am ple m argin fo r operational use. In the case of lightv essels a w ider v ertical beam w ill be n ecessary an yw ay owing to the rollin g o f the ship. A lthough this can be com pensated by simple m eans (gim bals) a w ider beam than 1,3 degrees seem s ad v isab le. A lso ligh tvessels w ill require an om nidirectional horizontal radiation p attern of the aerial. This can be achieved by a m o dification to the slotted w aveguide system. Concluding, the follow ing specification m ay be su g g e ste d : H orizontal p attern D ep en d s on local situation of R am ark. O n straigh t or alm ost straig h t coastlin es a 180 coverage is p referab le. This is easily achieved w ith a single slotted w aveguide. O n ligh tvessels 360 p attern s are required. M odification to the ae rial w ill provide a solution. V e rtical p attern E ssen tially only coverage of the horizon is n ecessary. T h erefore narrow beam high gain aerials are p ossib le (in the v ertical plane). H o w ev er w ith regard to frequency sw eep requirements and reduction of sidelobe interference on n earby ships (ow ing to sidelobes of the ships r a d a r aerial) the gain and vertical beam w idth should be lim ited. A com prom ise value is 4 5. O n ligh tv essels a w ider v ertical beam (15 20 ) is n ecessary or a simple stabilization of the aerial should be used (gim bals). P olarization H orizontal, since polarization for m arine r a d a r is horizontal. D iv e rsity T o reduce the in terferen ce effect a s m entioned in a d i versity system of tw o aerials has been tried in p ractice. A t the IJm uiden experim ents the top aerial w as a t 75 ft above mean sea level, the bottom one a t 54 ft. B oth aerials rad iate incoherent frequencies, which can be used to ad v an tage to in crease m ark space efficiency The ram ark tran sm itter (fig. 6). The nucleus of the tra n s m itter is the Philips m ultireflex k lystro n, which is show n with

21 A ramark beacon for use with marine radars 289 its asso ciated m agnet in fig. 7. This k lystron of all g la ss construction produces 10 W a t t s of continuous w ave R.F. pow er w ith operating voltages of 2 ]/2 to 3 k V. The efficiency is rath er high and am ounts to approx. 20 /0. The reso n ato r of this k ly stron consists of a Lech er system incorporating a conducting ribbon, perpendicular to the m agnetic field. The oscillating fr e quency of the k lystron is determ ined by the L ech er system and the position of the ribbon. W hen an altern atin g current, e.g. 50 cycles A C is fed through this ribbon, this elem ent sta rts to vib rate in the m agnetic field resulting in a fa st frequency sw eep o f 180 M c/s, the klystron covering b y these m eans the com plete m arine ra d a r band. The com plete equipm ent is housed in a stan d ard 19 inch rack and cabinet, which is ab out 4 feet high. In the top p a rt of the cabinet the o scillato r unit is housed. A frequency m eter and a pow er output m onitor are built in. The second ch assis from the top con tain s the m odu latin g circuits and a m onitoring o scilloscope fo r checking the m odulation and the perform ance of the k ly stro n over the frequency band. The av ailab le m odulation frequencies are c/s fo r the low frequency p a rt and 5, 10, 20, 40, 80 and 160 kc/s for the high frequency p art. The next ch assis contains the n ecessary sw itching gear, fuses and other protective m eans w ith asso ciate d pilot lam ps. The fourth one houses the voltage stab ilisatio n circuits, regu l ating the supply v o ltages fo r the m ultireflex klystron. The pow er units are located in the bottom p a rt of the cabinet. In this experim ental equipm ent a large num ber of built in m eters are provided for checking all im portant currents and voltages. The to tal pow er consum ption is 400 W a tts. 5. Conclusions The follow ing conclusions have been obtained during investigations w ith the abovem entioned equipment. It is estim ated th at 10 W a tts of R.F. pow er is sufficient for operation al use under all conditions. D urin g the trials sufficient evidence has been collected th at a d iversity ae rial system p ro vides the possibility to cancel the effects of minimum sign al zones. The judicious siting of the ram ark beacon e.g. 3 miles from n avigable channels w ill su b stan tially reduce the m asking effect

22 290 J. M. F. A. van Dijk, N. Schimmel and E. Goldbohm on a ship's P.P.I. In case this policy cannot be follow ed for obvious reaso n s, the F.T.C. circuit in marine r a d a r in conjunction w ith a ram ark beacon of ap p ro p riate H.F. ch aracteristics can be used to ad v an tage. It is known th at under certain circum stances distance inform ation is d esirab le. A beacon providing this facility opens the possibility to elim inate all beacon sign als on the P.P.I. betw een the ship and the beacon s position. The solutions, know n so fa r all suffer from satu ratio n of the be aeon and com plexity of the equipm ent either on shore or shipborne. B a se d upon the resu lts hitherto reached w ith the new type o f ram ark, which does not exclude the application of the re sponder principle, fu rth er developm ent w ork is in p ro gress which m ay lead, a s an altern ativ e solution, to a new type of beacon, giving range inform ation a s w ell, a t the sam e time takin g full ad v an tage of the featu res of the ram ark a s outlined in this publication.

23 September Deel 20 - No The Scenioscope * a new television camera tube by P. Schagen *) SUMMARY Further investigations on the image iconoscope type of television camera tubes have led to the development of a new camera tube, the Scenioscope. The target in this tube consists of semi-conductive glass, which makes the supply of negative charge possible from the signal plate through the target material to the surface of the target. The influence of the resistivity of the glass and of the thickness of the target sheet on the performance of the tube is considered. The sensitivity of the Scenioscope, which is at least five times as high as that of the image iconoscope, is also partly due to a considerably higher secondary-emission coefficient of the target coating. Perfect picture quality with a very low noise level can be produced with an incident illumination of a few hundred lux (f/d = 2), whereas recognizable though noisy pictures without appreciable spurious signals have been made with light levels as low as 15 lux. Introduction A few y e a rs ago some p ap ers on television cam era tubes w ere read a t a meeting of the N ed erlan d s R ad io G en o otsch ap, which w ere subsequen tly published in this journ al (1). From a com parison of the various cam era tubes, presen ted in these p ap ers, it ap p eared th at the im age iconoscope could produce excellent pictures, provided th at the illum ination level w as not much below ab out 1000 to 1500 lux. A lth ough this ligh t lev el is not difficult to e sta b lish in te le vision studios, the a rtists m ay find the com paratively high tem p eratu re, due to the generation of h eat by the lam ps, som ew hat troublesom e. In th eatres etc., w here the norm al illum ination of the stage is insufficient for this purpose, the in stallation of extra lighting for a television b ro ad c ast is a rath er expensive and som etim es a lso a difficult p ro ced u re. The only television cam era tube capable of producing accep tab le picture quality a t an incident illum ination level of a few *) Philips Research Laboratories, N.V. Philips Gloeilampenfabrieken Eindh oven-netherlands

24 292 P. Schagen hundred lux ap p eared to be the im age orthicon. A p a rt from its higher sensitivity, how ever, this tube show s some distinct d isad v an tages com pared w ith the im age iconoscope. F o r this reason furth er in vestigation s w ere m ade in several research lab o rato rie s in E u rope, w ith the aim o f increasing the sen sitivity of the im age iconoscope, while a t the sam e time m aintaining its excellen t p ictu re q u ality. In the Philips' R esearch L a b o ra to rie s a t Eindhoven, these in vestigation s have resu lted in the developm ent of a new television cam era tube, the Scen ioscope" (2). A lthough this tube show s a close resem blance to the im age iconoscope type its outw ard dim ensions are exactly the sam e -, a fundam ental difference in its mode o f operation h as yielded a gain in sensitivity of a t le a st a fa cto r 5 over the im age iconoscope. F u r therm ore the ultim ate limit to the use oi the Scen ioscope" a t Fig. 1 Diagrammatic cross-section of the image iconoscope. L - lens; P < - photo-cathode; 5 < - coil of the magnetic electron lens; T target (mica); C collector; E > - scanning beam supplied by an electron gun of which only the cathode, K is shown in the diagram; F focussing coil; D deflecting coils; S P signal plate; R s signal resistor. low light levels is set by the decreasin g signal-to-noise ratio and no longer by the spurious signals, which ap p eared in the im age-iconoscope p ictu res. The Scen ioscope" produces excellent pictures, p ractically free o f noise, a t an incident illum ination lev el o f a few hundred lux, w h ereas during lab o rato ry te sts noisy though recognizable pictures have been m ade w ith light levels a s low a s 15 lux.

25 The Scenioscope, a new television camera tube 293 The im age iconoscope The mode of operation o f the Scenioscope m ay be explained b y first b riefly recallin g th a t o f the im age icon oscope. In this tube (see figure 1) an optical im age is projected on a sem i-tran sparen t photo-electric cathode. B y m eans of a combined electric and m agnetic lens every photo-electron, em itted under illum ination by a certain picture elem ent on the photocathode, is accelerated and directed to a corresponding elem ent on the target. The photo-electrons striking the ta rg e t release more than one secondary electron each, thus form ing a positive charge im age on the target, which is scanned by an electron beam, stabilizing one t a r get element a fte r another a few volts above collector potential. P a rt o f the slow secon dary electrons, released b y fa st photoelectrons or by the scanning beam, are captured by other ta r get elem ents, w here the poten tial m ay locally be even higher than collector poten tial. This redistribution effect is respon sible for the grad u al drop in potential o f each ta rg e t elem ent betw een successive scan s. A s this poten tial becom es low er, the energy of an increasing Fig 2 Effective secondary emission factor ipejf) of an insulator, plotted against the energy ( of the primary electrons. & eff 1 when Potential Vpr V1 or Vpr Eg 3 is one or two volts higher than the collector potential Vcoll* Vo is the potential at which the flow of secondary electrons to the particular target element is completely cut off. p a rt of the secondaries, released by the photo-electrons, is sufficiently high to let them escape to other ta rg e t elem ents or to the collector. The effective secon d ary-em ission coefficient, àeff> thus in creases and so does the contribution o f each photo-electron to the ch arge im age. Figure 2 show s schem atically the relation betw een beff and the poten tial of a targ e t element, w h ereas figure 3 show s, also schem atically, the poten tial variation of a ta rg e t elem ent betw een successive scan s, with and w ithout illumination

26 294 P. Schagen Lim itations to the sensitivity o f the im age iconoscope Fig. 3 Potential V of a target element in the image iconoscope, plotted against the time t, in the frame period between two scannings. Curve drawn as a solid line: photo-cathode not illuminated. Curve drawn as a dotted line : photocathode illuminated. Both curves start at the stabilizing potential Vstab ( V2, The redistribution effect ap p ears to be essen tial for the operation of the im age iconoscope. W ith o u t the re sulting drop in poten tial the ta rg e t elem ents, once stab ilized, w ould indefinitely retain their stabilization potentialw ith beff 1- under electron bom bardm ent. This effect, how ever, also se ts the lim it to the sen sitiv i ty of the im age iconoscope fo r the follow ing reaso n s: a. Since the fa ll in poten tial see fig. 2) and approach V 0 asymptoti o f a ta rg e t elem ent is entirely cally. By the end of interval V determ ined by the lim ited drops to V'0 or V"Q. The contribution to the output signal is V 0 > f V'0, num ber of slow electrons cap tured by this element, the effective secondary-em ission coin creases only g rad u ally from efficient of the photo-electrons beff ~ 1 d irectly a fte r each stab ilization by the scanning beam. The illum ination can th erefore not be a s effective a s it w ould have been if the poten tial dropped more rapidly. b. ^V ith increasing illum ination the poten tial of the ta rg e t elem ents falls even more slow ly and these elem ents w ill, as a resu lt, a ttr a c t more redistribution electrons which p artly neutralize the effect of the photo-electrons. c. F o r different p a rts of the ta rg e t the redistribution current to the ta rg e t elem ents v aries, resulting in the production of,,spurious sig n als, which do not correspond to the illumination. T hese spurious sign als only d ecrease both in ab solu te value and relative to the picture sign al w ith increasing illum ination. The minimum light level, w here the im age iconoscope can still produce an accep tab le picture, is therefore determ ined b y the presence of these spurious sign als and not b y the decreasin g sign al-to-n oise ra tio.

27 The Scenioscope, a new television camera tube 295 P ossible methods o f in creasin g the sensitivity A m ethod o f in creasin g the sen sitiv ity o f the im age iconoscope follow s directly from the above considerations. I f the potential of a ta rg e t elem ent can be m ade to fa ll more rap id ly a fte r stabilization, the effective secondary-em ission coefficient, def/, of the photo-electrons w ill reach its maximum value sooner and the photo-electrons can, as a result, contribute more to the form ation of the charge im age. In creasin g the beam current A possible w ay of obtaining this effect seem s to be given by increasing the redistribution current. This m ay be achieved b y increasing the current o f the scanning beam. The signal output of the tube does in fa c t rise w ith the beam current, but only to a limited extent, since the in creased redistribution current is more a ttracte d by the illum inated elem ents with their higher poten tials. The signal-versus-beam current curve show s a maximum (3), w h ereas the spurious sign als increase even more rapid ly than the picture signal, m aking this m ethod im practical. The drop in potential w ill therefore have to be achieved by m eans of a supply of negative charge to the targ e t elem ents, which is independent of the scanning beam. Show ering the target w ith slozv electrons A more p ractical solution of this problem h as been reached in the B ritish P.E.S.-p h otico n (4) (P h oto-e lectrically-stab ilized ) the G erm an R iesel-ik on o sk o p (5). In this tube the envelope surrounding the ta rg e t has been provided w ith a sem i-tran sparen t photo-cathode, which is kept a t co llecto r p o ten tial and is illum inated by a circle o f in can descent lam ps. The resulting drizzle (hence the G erm an name) of slow photo-electrons reach es the target, w here a few auxiliar3r anodes, placed along the sides, direct m ost of these electrons to those p a rts of the targ e t, w here the redistribution cu rren t is too sm all. The initial in crease in sen sitiv ity, ca u se d by the more effective secondary em ission of the photo-electrons, is p artly counteracted, how ever, by the preference of the slow electrons for the illum inated ta rg e t elem ents w ith their higher poten tials. O n

28 296 P. Schagen the other hand an im portant ad v an tage over the norm al image iconoscope is the n early com plete absence of spurious signals. F o r this reason the P.E.S-p h oticon is claim ed to need about h alf the illum ination of the im age iconoscope fo r good picture quality. Supplyin g negative charge through the target W ith the tw o above m ethods of forcing the poten tial of the ta rg e t elem ents to fall more rap id ly a fte r each stabilization, negative charge is supplied by slow electrons reaching the elem ents from outside the targ e t. A nother p ossibility is the supply of negative charge through the ta rg e t itself. The idea o f employing a ta rg e t with some slight conductivity w as originally p roposed both in E n glan d and in G erm any, before the secondvworld w ar, to increase the sen sitivity of the iconoscope, and w as first realised in an experim ental tube, the,,h alb leiter- Ik o n o sk o p (6). B ecau se this principle w as not applied in the m ost ad v an tageous manner, how ever, it never led to a p ractical tube. In the P h ilips R esearch L a b o ra to rie s the principle of supplying negative charge through the ta rg e t has been applied to the im age iconoscope. This h as resu lted in the developm ent o f the Scen ioscope, which w ill now be discussed in more detail. Mode o f operation T h e S c e n i o s c o p e The fundam ental difference betw een the Scen ioscope and the im age iconoscope is found in the ta rg e t structure. The thin sheet of insulating mica in the im age iconoscope has been re placed by a slightly thicker sheet of sem i-conductive g lass, which is b acked w ith a conducting layer, the signal plate. A photograph of a m ounted ta rg e t is show n in figure 4. The sign al p late is given a low er poten tial than the collector anode, w h ereas the ta rg e t elem ents are stabilized by the scan ning beam a t a few volts above collector potential. The re su l ting poten tial difference betw een the ta rg e t elem ents a t the surface and the signal p late a t the b ack of the ta rg e t sheet cau ses a current to flow through the targ et, which p artly d isch arges the ta rg e t elem ents betw een successive scans. The p o ten tial of these elem ents will, a s a resu lt, fall more rap id ly a fte r each stabilization. The ta rg e t elem ents now only capture re d istribution electrons while their poten tial is not more than a few volts

29 The "Scenioscope, a new television camera tube 297 I lie target I rom 50 to scanned is of the,,scenioscope is a skin 70 it thick, on a metal ring. The 45 x 60 mm. I he signal plate is a ol slightly conductive size of the rectangular layer of metal on the glass area back of the target. below stabilization potential, w h ereas the discharging current through the ta r g e t continues to flow throughout the time b e tween tw o successive stabilizations, provided that the re la x a tion time R 0C0 o f the ta rg e t m aterial is sufficiently long com p are d w ith the tram e period. Since the current through the targ e t is independent of the location o! the element on the target, this current does not cause spurious signals. The redistribution current to an element should therefore be kept as sm all a s possible, com pared with the current through the target to avoid these spurious signals. This is a fundam ental dilference with the image iconoscope, where the redistribution effect is essen tial. In the Scen ioscope it is only a secondary efleet, which has to be avoided a s much as possible. The schem atic diagram in figure 5 show s the poten tial of a

30 298 P. Schagen Fig. 5 / and 2 arc V f(t) curves, as shown in hg. 5, lor the image iconoscope, j and ^ refer lo the Scenioscope, with slightly conductive target, signal plate potential negative, y lor a non-dluminated, and lor a faintly illuminated photo-cathode. targ e t elem ent, w ith and w ithout illumination, betw een tw o successive scans. The corresponding curves lor an im age iconoscope have a lso been given a g a in lo r com parison. From the above con siderations it lollow s th at a rapid tall in potential of the targ e t elem ents is d esirab le lo r tw o r e a s o n s: a. The effective secondary-em ission coefficient, dr/ / f of the ph oto-electron s w ill reach its maximum value soon er, thus increasin g the se n sitiv ity of the tube.

31 The Scenioscope, a new television camera tube 299 b. The redistribution current w ill be sm aller and spurious sign als w ill therefore be avoided. There are tw o w ay s of increasing the speed at which the poten tial of the ta rg e t elem ents d r o p s : increasing the current through the targ e t, and d ecreasin g the capacitan ce of the t a r get elem ents to the sign al plate. The perm issible current through the ta rg e t is limited b y electro ly sis of the g lass, which cuts dow n the life of the tube. Furtherm ore local sm all differences in ta rg e t thickness m ay cause spurious sign als of a different nature, the am plitude ol which is, of course, proportion al to the current through the target. A d ecrease in capacitan ce of the ta rg e t elem ents to the sign al plate corresponding to an increase in ta rg e t thickness is lim ited by the requirem ents of good picture resolution and ol a d esirab le gam m a in the output ch aracteristic, as w ill be show n late r. The resistivity an d thickness o f the target Since the targ e t m aterial in the Scen ioscope is not completely insulating, but sem i-conducting, p a rt of the positive charge built up b y the photo-electrons on the various targ e t elem ents w ill also be lo st by conduction before the next scan ning. The effect of this conduction on the charge im age has been studied in a recent p ap er (7), the resu lts of which w ill be sum m arized here. The conductivity of the targ e t m aterial h as tw o effects on the charge im age. In the first place, im age charge w ill leak through the ta rg e t to the signal p late and w ill be lo st before it can be rem oved by the scanning beam and contribute to the output signal of the tube. This resu lts in a lo ss of sen sitivity, which is determ ined b y the relaxation time R 0C0 of the targ e t m aterial, w here R 0 is the resistan ce and C0 the capacitance betw een the su rface of the ta rg e t and the signal plate, both per unit targ e t area. Figure 6 gives the relativ e sign al output as a function ol r/r 0C0 w here r denotes one fram e period (0,04 sec in the E u ro peon telev ision sy ste m s). I f the lo ss of sen sitivity m ay not be more than about 10(>/0, figure 6 show s th at the value of r/r 0C0 m ust not exceed 0,25. W ith a d ielectric co n stan t o f the g la s s of 6 to 8, this condi-

32 300 P, Schagen Signal current (ƒ* : on relative scale), plotted as a function of t/r 0C0, for values of J\0 and Co consistent with an Is equal to 90 /0 of the maximum value (t/r oco= 0.25). tion requires a minimum specific resisitiv ity p of the g la ss of p f2cm. O n the other hand p should not be too high, since this might, fo r the sam e targ e t current, introduce picture defects a t the edges ol targ et, which w ill be d iscu ssed later. The upper limit of p has therefore been chosen a t about p = 1012 Qcm. *) Secondly, positive charge w ill flow from ta rg e t elem ents w ith m ore illum ination to n eighbouring elem ents w ith le ss illum i nation, w here the p oten tial is low er. This is a conduction current across the target, resulting in a loss of picture resolution, which n atu rally affects the sm allest picture d etails m ost. If, fo r instance, the picture w ere to con sist of altern atin g strip s ]with more and less illum ination and a given co n trast, this conduction acro ss the ta rg e t w ould d ecrease the depth of m odulation in the charge im age w ith decreasin g w idth of the strip s. In order to stu d y this effect more closely, a relative depth of m odulation M m ay be defined as the ratio of the depth of m odulation in the charge im age ju st before the next scanning for a w idth D of the strip s to th at w here h alf the ta rg e t is *) N.B. The specific resistivity of glass varies with the temperature. The values of p mentioned above apply to the working temperature of the tube, which should therefore be kept between certain limits. For the Scenioscope this temperature range has been chosen between 35 and 45 C. The corresponding values of o at room temperature are roughly between 1012 and Qcm.

33 The Scenioscope, a new television camera tube 301 R elativ e m odulation depth AI o f the potential im age on the target, plotted again st A / D (A = thickness o f target, /) w idth o f beam s in a picture com prising b lack and w hite beam s), w ith t/r 0C0 as p aram eter. F o r r/roco = 0.25, the value 1. A /D m ust not exceed roughly R elati ve m odulation depth M in the output signal o f the S cen io sco p e in the centre o f the picture, plotted again st the num ber o f lines per fram e N. illum inated and the other h alf is not. M m ay then be calculated for different valu es of r/r 0C0 as a function of A /D, w here A rep resen ts the thickness of the target. The re su lts ol th is calcu latio n a re laid dow n in figure 7. The diam eter ol the sm allest d etails in the picture is equal

34 302 P. Schagen to the diam eter of one picture elem ent, corresponding to the w idth of one scanning line. F o r a television system w ith 625 lines, this diam eter equals about 75 [x on the ta rg e t of the Scen ioscope. If the relative depth of m odulation M in the finest d etails of the charge im age on the ta rg e t is not allow ed to be more than 10% sm aller than on an insulating target, figure 7 show s th at w ith r/r 0C0 = 0,25, A /D should not exceed the value 1. The thickness of the ta rg e t A should therefore not be more than ab o u t 75 ju. In the "S c e n io sc o p e / A lies betw een 50 and 70 fx and the picture resolution actu ally o b tained differs v ery little from th at obtained w ith the im age iconoscope. Figure 8 show s the relativ e depth of m odulation in the uncorrected output sign al of the Scen ioscope for the centre o f the p ictu re a s a function o f the line num ber. The influence o f the negative sig n a l p late The electric field above the su rface of the target, which d raw s the secondary electrons to the collector, determ ines the stabilization poten tial of the various ta rg e t elem ents. W ith o u t special precaution s the field n ear the edges ol the scanned ta rg e t are a might be con sid erab l3r reduced b y the influence of the negative sign al p late. This w ould lead to a low er stabilization poten tial for these elem ents. The current through the ta rg e t w ould be sm aller and the scanning beam w ould accordingly deposit less positive charge during stabilization, sim ilar to the effect of more illum ination. In order to avoid bright edges show ing in the reproduced picture, it ap p e are d d esirab le to surround the scanned ta rg e t a re a w ith a conducting fram e, which can be given a poten tial sligh tly below th at of the collector, thus effectively screening the negative signal p late. I h e adjustm ent of the scanning p attern on the ta rg e t w ithin this surrounding fram e becom es more critical, how ever, w ith an increasin g negative p oten tial on the sign al p late. F o r this reason the specific resistiv ity of the ta rg e t m aterial for a predeterm i ned ta rg e t current is lim ited, as w as mentioned above. The output ch aracteristics o f the Scenioscope O nce the resistiv ity of the ta rg e t m aterial and the thickness of the ta rg e t have been chosen, the ta rg e t current depends on the negative poten tial of the signal plate. This current de-

35 The Scenioscope, a new television camera tube 303 C u rve d raw n a s a solid lin e : I s as a function oi Ifth fo r the S cen io sco p e, w ith the leak age current II through the g la ss target a s a p aram eter (ƒ/ m easured in d ark n ess). C u rve d raw n a s a dotted lin e : Is for im age iconoscope term ines the maximum output signal of the tube, because for the elem ents w ith the highest illum ination the photo-current can, a t m ost, replace the charge leaking a w a y to the signal p late. W ith a sufficiently high ta rg e t current the poten tial of a ta rg e t elem ent with little illum ination fa lls so rap id ly th at be/ f reach es its maximum value dmax sh ortly afte r each stabilization. The output ch aracteristic of the tube, show ing the sign al current I s as a function of the photo-current Iph> is a t first a straigh t line (gam m a = 1). W ith increasing illum ination the drop 1n poten tial of a targ e t elem ent d ecreases and de/ / of the photoelectrons reach es its maximum value later, while finally bmax s not reached a t all. A s a resu lt the output ch aracteristic show s a grad u al satu ratio n, the shape of which is determ ined

36 304 P. Schagen b y the capacitan ce of the targ e t. F o r a sm aller capacitance (thicker targ e t) and equal ta rg e t current, the satu ration a p p ears a t higher photo-currents, and the ch aracteristic will bend more sh arp ly. AVith a g re a te r cap acitan ce the poten tial drop is sm aller and the satu ratio n sets in a t low er photo-currents and is of a more g rad u al nature. This sligh tly reduces the sen sitivity (less signal-current for equal photo-currents) but offers tw o ad v an tages. In the first place the gam m a of the tube is now sm aller than unity for a g re a te r p a rt of the output ch aracteristic, sim ilar to th at in the im age iconoscope, thus com pensating lo r the gam m a ^>1 of the cath o d e-ray tube. T he output sign al needs no gam m a-correction in this c a se. The second ad v an tage of the more grad u al satu ratio n in the output ch aracteristic is gained by the fa c t th at the -maximum output signal now correspon d s to much higher photo-currents, thus increasing the co n trast ran ge in the scene which the tube can still reproduce. W ith the perm issible ta rg e t current of ab o u t 0.5 jua and the chosen ta rg e t thickness of 50 to 70 ju, the sh ape of the output ch aracteristic ap p eared to be very favou rab le. Som e rep resen tativ e curves are given in figure 9 lo r three values of the ta rg e t current. The ty p ical output ch aracteristic of the im age iconoscope type 5854 has also been given lo r com parison. Sen sitivity W h e re as the increase in sensitivity of the Scen ioscope over the im age iconoscope is m ainly due to the m easu res d ealt with above, an im portant gain in sen sitivity h as also been achieved by the con siderably higher secondary-em ission coefficient of the target. It ap p eared possible to cover the su rlace of the g lass ta rg e t sheet with a very thin lay er of m aterial w ith a d,nax of 10 to 11, com pared w ith the value of 4 to 5 in the im age iconoscope, w here the mica ta rg e t sheet w as coated w ith a thin la 3rer o f m agnesium oxide. The output ch aracteristic of figure 9 show s th at the sen sitivity of the Scen ioscope is not fa r below the maximum sen sitivity which is th eoretically possible with such a sy ste m : the ratio of I sjiph a t the low er end of the ch aracteristic is about 7, w hereas the theoretical value of Isjlph for bmax = 1 0 equals about 11.

37 The Scenioscope", a new television camera tube 305 W ith decreasin g illum ination the picture quality d eterio rates only by the d ecrease in signal-to-noise ratio and not b y the spurious sign als, a s with the im age iconoscope. P erfect picture q u ality can be produced a t an incident illum ination level on the scene of a few hundred lux w ith a lens of f / D = 2. *) In lab o rato ry te sts w ith some tubes this picture quality w ith a very low noise level could even be m aintained below 100 lux, and recognizable though noisy pictures w ere m ade with light lev els a s low a s 15 lux. A p a rt from the difference in sensitivity, the Scen ioscope and the im age iconoscope w ill obviously have sev eral featu res in common, since the photo-cathode, the electric and m agnetic lens, and the electron gun providing the scanning beam are identical. The m ethod of varying the field of view with electrical m eans (electric zoom " lens (8)), discussed in the p ap er on the im age iconoscope ( 1), can also be applied to the Sceniosco p e. References 1) H. Bruining, P. Schagen en J. C. Francken, Opneembuizen voor televisie. Tijdschr. N ed. R adio Gen. X V I-5, Sept ) P. Schagen, J. R. Boerman, J. H. J. Maartens en T. W. van R ij s s e 1, De Scenioscope, een nieuwe opneembuis voor televisie, Philips T ech. Tijdschr. 17, 173^ 182, Juni ) P. Schagen, On the mechanism of high-velocity target stabilization and the mode of operation of television camera tubes of the image-iconoscope type, Philips Res. Rep. 6, , ) ]. E. Cope, L. W. Germany and R. T h e i 1e, Improvements in design and operation of image iconoscope type camera tubes, J. Brit. Inst. R ad. E n grs. 12, , ) R. T h e i 1e, D ie Signalerzeugung in Fernseh-Bildabtastrohren, Arch, elektr. U ebertragung 7, 15 27, und , ) G. K r a w i n k e 1, W. Kronjager und H. S a 1o, Ueber einen speichernden Bildfanger mit halbleitendem Dielektrikum. Z. techn. Phys , ) P. Schagen, Limiting resolution due to charge leakage in the scenioscope, a new television cam era tube, Phil. R es. Rep. 10, , June ) J. C. Francken and H. Bruining, Nieuwe ontwikkelingen aan de beeldiconoscoop, Phil. Tech. Tijdschr. 14, no 10, , Oct *) It h as to be taken into account that the u sefu l a re a o f the photocathode in the Scen io sco p e, as w ith the im age iconoscope type 5854, h as a diam eter o f 2 cm. The depth o f focu s in the p ictures o f the scen ioscope w ith f / D 2 is therefore com p arab le to that in the p ictu res o f a tube w ith a diam eter o f the photo-cathode o f 4 cm (like the im age or- thicon) w ith a lens apertu re f / D = 4.

38 I

39 September Deel 20 - No Electromagnetic Theory of Moving Matter II by E. J. Post * ) SUMMARY The p resen t p ap e r develops program m e B o f the previou s p ap e r and p roceeds from the first order com patible G alilei kinem atics and the no aeth er point o f view. The developm ent benefits from a general distinction betw een p h ysical quantities applyin g in general to phaenom enological theory. T h is distinction, w hich is b ased on the N eum ann principle o f cry stal physics, su ggests a d e finition o f state q u an tities and m atter q u an tities. The discu ssion sh ow s that state quantities a p p e ar only in the field equations and the tran sfo r m ation form ulae o f the state quantities. The equations o f state on the oth er hand con tain both q u an tities. The application o f these principles e ase s the w a y to the m athem atical form ulation given in the previous p ap er. In the la st sections, theory B is applied to som e cases w hich cannot be solved by m eans o f the usual classical form alism labelled as program m e A in p art I. Introduction A s mentioned in the previous paper, the im possibility of e sta blishing a velocity with resp ect to em pty space is contained in the tran slatio n al invariance of the em pty space perm eabilities e an d /t. o o The other startin g point, the G alilei kinem atics, is contained in a general kinem atical form ula, which w ill be discussed a t the beginning o f the n ext section an d ap p en d ix I. The distinction and definition of state and m atter quantities is covered by the follow ing r u le s : I. A state quantity gives inform ation about the state of a medium, independent o f its p ro p e rtie s. II. A m atter quantity gives inform ation about the p ro p o rties of a m ed ium, independent of its state. The criterion fo r this distinction is indicated b y the ap p lication of the N eum ann principle. The m atter quantity is subjected to the N eum an n prin ciple, the sta te q u an tity is not. The N eu- * ) C en tral L ab o ra to rie s N eth erlan d s P.T.T.

40 308 E. J. Post mann principle claim s th at an y physical p roperty of m atter should be in varian t fo r the group of sym m etry operations determining the sym m etry class of the substance in question. E lectric and m agnetic fields are state quantities in the sense of this distinction, relative perm eabilities e and fx are m atter quantities. The la tte r are diagon al ten sors w ith identical elem ents on the main diagon al fo r isotropic (and cubic) su bstan ces only (see appendix II- fo r application s of the N eum ann principle). R ule I im plies the follow ing rule about the tran sform ation equations of sta te quantities. I I I. The tran sform ation equations of state quantities are independent of the nature of m atter, otherw ise they w ould co n trad ict rule I. A sim ilar statem en t can be m ade about m atter quantities. IV. The tran sform ation equations of m atter quantities are independent of the sta te of m atter, otherw ise they w ould con tradict rule II. R u les I I I and I V are obvious and w ell know n fo r a ro ta tional change of coordinates, the direction cosines are the p a r a m eters of the tran sform ation in this case. They are, how ever, equally true fo r a tran slatio n al change of coordinates, the mutu al velocity of the coordinate system s being the p aram eter of the tran sform ation. The preceding considerations su ggest the follow ing classification of electrom agnetic m edia, including em pty space. a. Em pty sp ace: The equations of state D = ee and B = (1) o o are in varian t fo r the group of ro tatio n s, im proper rotation s and tran slatio n s of coordinate system. b. Isotropic m atter : The eq u atio n s of sta te D = e e E and B = y [i IT (2) o o are defined w ith resp ect to a coordinate system fixed in the su bstan ce. They are in varian t for the group of p roper and improper rotation s only. c. A nisotropic m atter: The equations of state D = e e H and B = f t (x H (3) O o are defined w ith resp ect to a coordinate system fixed in the

41 Electromagnetic Theory of Moving Matter II 309 su b stan ce. They are invariant fo r the group of sym m etry operations of the medium in question. The m atter quantities e and ft are ten sors with, a t m ost, six independent elem ents, if there is no sym m etry. It w ill be clear from equations ( 1), (2) and (3) th at the equations of state contain sta te quantities as w ell a s m atter quantities. The state quantities of a medium are re quired to s a tisfy the field eq u atio n s. It w ill a p p e a r in the next section th at field equations contain state quantities only. This lead s to the follow ing r u le s : V. A field equation is independent of the nature of m atter and independent of its motion. V I. An equation of state relate s the sta te of m atter to its p roperties,an d henceforw ard contains both state quantities and m atter quantities. The fe atu res sum m arized in the six given rules are useful notions to keep in mind fo r an easy developm ent of program m e B. The physical p aram eters of em pty space e and fx are obvio o ously not regard ed as m atter quantities. Im proper definition of state quantities as w ell as poor inform ation ab o u t the equations of state m ay im pair the form al distinction m ade in this section. T h e so called piezo-electric effect of some isotropic su b stan ces (B arium T itan ate) f.i. is the product of the electrostrictive properties and the biasing field. It w ill be clear th at this lead s to m atter quantities imp ro p e rly defined in the sen se o f this section. 2. T ran sform ation equations an d fie ld equations E xperim en tal observations are m ade on physical sy stem s of finite size rath er than on fields. The in tegral law s of F arad a y - M axw ell, and M a x w e ll s extension (displacem ent current) of the law of B io t-s a v a rt, are the resu lt of o b servations on m acrop h y sical system s. The m athem atical an aly sis of these circuital law s invokes the concept of the time derivative of flux. The flux xp is related to a corresponding vectorfield A b y the su rface in te g r a l: V = ƒ A. d a (4) A change of xp w ith time can be brought about by tw o independent sources i.e. the intrinsic change of the field A w ith time and the change in position and shape of the su rface o

42 310 E. J. Post w ith time. The differentiation is expressed by the follow ing w ell estab lish ed m athem atical form ula, if the tw o sources operate sim ultaneously (see appendix I). 4 curl (AXv) 4 v - div d a tics. The first term in the in tegran t This theorem is b ase d on the principles of G alilean kinemada correspon ds to the indt trinsic change w ith time of A, the others are cau sed by the motion of the surface o w ith the velocity v. It is im portant to note th at the integration and differentiation commute, only if the m otion is uniform. E quation (5) provides the essen tial m athem atical tool to tre a t the circuital law s in their gen eral form. They a r e : E '.d% B. da F a ra d a y -M a x w e ll (6) H \ d % - o S D. da o B io t-s a v a rt (7) The line in te g ra ls in the le ft hand m em bers w ith line element d\ are su pposed to be the resu lt of experim entel o b servation. The contour of these in tegrals m ay be in motion with resp ect to the chosen coordin ates. This su ggests th at the m easurem ents are m ade in a fram e of reference having a velocity w ith resp ect to the original coordin ates. The sym bols E ' and IT are, therefore, provided w ith a dash to em phasize this distin ction. The sam e holds fo r the current den sity s', as the current is defined as the am ount of charge p assin g the aforem entioned con tour p er unit o f tim e. The situation is different in the right hand m em bers w ith the m agn etic an d electric inductions. I t w ill be c le a r from the considerations in appendix I th at the fields B and D are defined in the chosen coordinate sy stem itself. The application of S to k e s' law and theorem (5) to the eq u a tions (6) and (7) giv es: f curl (E ' v X B ). da / x. da ) o (8) curl (H ' + v X D ) d a = f9d ) ^ 4- s da, (9)

43 Electromagnetic Theory of Moving Matter II 311 use being m ade of the fa ct th at the divergence of the m agnetic induction d isap p ears, w h ereas the sam e operation on D yields charge density q. *) A statio n ary contour of the line in tegrals w ould have led to the e q u a tio n s: curl E. da o c) :"_B. da ot ( 10) curl H. d a = O D. do + ƒ s. do, I Ool ( 11) containing a set of coherent field quantities. U sin g the term i nology of the previous section w e m ay s a y ; the state quan tities E, B, D, H and s are all defined w ith resp ect to the sam e fram e o f referen ce. It is obvious th at the follow ing tran sform ation s are sufficient to reduce the equations (8) and (9) to (10) and (1 1 ): E ' = E + v X B ( 12) H' = H - v X D (13) s' = s - qv (H ) The corresponding field equations fo r a set of coherent state quantities are consequently: curl E = B (15) curl H = s + 3D a/ (16) The n ecessity of the form ulae (12), (13) and (14) is su ggested if we consider, th at the tran sform ations should form a group i.e. the resu lt of tw o consecutive tran sform ation s again should have the form a s given in (12), (13) and (14), the velocity p aram eter being the vectorial sum of the velocities of the tw o individual tran sform ation s. This togeth er w ith the requirem ent of the existence of an identical tran sform ation, restricts v ery considerably the possibilities for the addition of an arib itrary gradien t field (curl grad = 0) in the form ulae ( 12) and (13). The an aly sis of the group properties of the equations ( 12), (13), m oreover, inform s us ab o u t the first-order nature of the tran sform ation i.e. all term s of second-order and higher should *) The divergence la w s are not affected by a tran slation.

44 312 E. J. Post be discard ed. This w as to be expected, recalling the G alilean kinem atics a s one of the startin g points of the theory. The derivation of the tran sform ation s and field equations has been independent of the presence of m atter, confirming the rules I I I and V of the previous section. M oreover, if the eq u a tions ( 12) and (13) are true in em pty space, they still hold ii w e m ultiply them w ith the em pty space perm eabilities e and /jl. o o U se of the tran slatio n al invariance of the la tte r lead s to : D' = D + efivx H (17) o o B' = B - ejuvx E, (18) o o application of rule I I I a ssu re s their independence of the p re sence of m atter. The first circuital law can be ex p ressed in term s of a sc ala r and a vector potential, thus enabling the right hand m em ber to be tran sform ed into a line integral. U se oi the corresponding theorem fo r the differentiation of a line in tegral (see ap p en dix I form ule V I ) lead s to a tran sform ation of the sc a la r p o ten tial op. op = op v. A, (19) A being the vector potential. It is a peculiar featu re th at (19) like (14) is not subject to first-order restriction s to m aintain its group p roperties. The charge d en sity q and the vector p oten tial A on the other hand have the p ro p erty of being (G alilean ) in varian t for tran slatio n s. 3. The equations o f state o f non-conductive isotropic m atter The equations of state of moving isotropic m atter are easily derived using the tran sform ation form ulae (12, 13, 17, 18) and the equations (2) fo r statio n ary isotropic m atter. I f we tak e the reference system X ' fixed in m atter, the equations of state w ith resp ect to this system are B ' = pcpt H \ D = ee E ' (2a) o o Introducing a coordinate system X having a velocity u with resp ect to X ' fixed in the m aterial medium y ie ld s: (B spivl XE) = pijj, (H u X D) o o o (20) (D 4- sfiu X H) = e(e + u X B ).

45 Electromagnetic Theory of Moving Matter II 313 The equations (20) constitute the equations of state of a moving body. It is possib le to tran sform (20) into an other first-order form which is more elucidating from a p h y sical point of view. R earran gem en t of the term s in (20) g iv e s: B = /jl/jl H + e/m X E jujuu X D o oo o (21) D = E /Al X H + U X B. o o o o The equation (21) expresses the inductions B and D in the field strength s H and E except fo r the la st first-order term s in the right hand member /jlfixx X D and + U X B. B ecau se o o of the first-order nature of (21) the D and B in the latte r term s can be replaced b y the zero-order approxim ations B = fi/m H and D = E. The resulting equation, w ritten in an apo o propriate "fo u rterm in al" ap p earan ce, is the desired equation of state of moving isotropic m atter. D = E [ilfl l l o o JU ) u X H B = + JUJU I ux E + o o [X F o r [x I, the equations (22) are reduced to the em pty space equations of state (1), and as is to be expected, u = O m akes (2) the equations of isotropic statio n ary m atter. It should be noted th at F resn el's convection coefficient I, a p p e a rs \ as a ty p ical featu re in the cross-coefficients of (22). It is convenient to have the inverse set of eq u atio n s: E = D + (i - uxb \ U J i (23) H = -fi - - U X D + - B \ fl J fl JU The cross con stan ts in (22) and (23) rep resen t the "g y r o scopic" properties of moving m atter. It is interesting to know th at a fourterm inal device b ase d on the sim ultaneous application of the R öntgen and W ilso n effects w ill constitute a non-reciprocal netw ork. Tellegen (1) p o stu lated the follow ing relation betw een the state quantities of a hypothetical non-reciprocal statio n ary medium.

46 314 E. J. Post D = s E + y H B = y E + /jl H The fe asib ility of statio n a ry m atter having a y 7^ O d eserves a discussion from the point of view of the second law of th erm odynam ics. A n application of N eum ann's principle show s th at a gyroscopic" effect (coefficient y) cannot exist in statio n ary isotropic m atter (see appen dix II). There are still other se ts of equation s of state with E, B and D, H, resp ectiv ely a s the dependent v ariab les. This lead s to the follow ing e q u a tio n s: E = B = D + juju (1 - ) u X H fl o + juju i u X D + ^ H /LL (25) D = E ( 1 ] U X B o o \ jbi J H = - eeii )u X E + B O \ fl j fll ju This la st choice of v ariab les is more ap p ro p riate fo r the an aly sis of w ave motion in moving m atter. 4. Wave propagation in m oving 7ion-conductive isotropic m atter The gen eral case of a rb itra ry directions of convection and w ave p ro p agatio n is som ew hat cum bersom e and involved. The essen tials, how ever, m ay be studied fo r the one dim ensional case. The elim ination of the succesive sta te quantities betw een the M ax w ell equations and the equation s of state gives the follow ing asym m etric w ave eq u atio n : I d2 fl/bi dx2 o o a/2 - f - 2V I - /U a a 1 (27) The function ip stan d s fo r any of the sta te quantities. A w ave solution xp = yj exp i(cot kx) o co = circu lar frequency k = w av e num ber (28)

47 Electromagnetic Theory of Moving Matter II 315 y ield s the frequency equation k co2 = EEJUjU 2V 1 _ \ (okt (29) Solving for the phase velocity u cojk and rem em bering th at first-order term s should be m aintained only, lead s indeed to the correct form ula of d rag I ---- ) ; u 1 / { in medium ( 3 0 ) EfX) ) EE/UjU \ at rest o o An experim ental check of this form ula for electric and m agnetic perm eable m aterials su ggests an experim ent in the range o f cm w avelength s. Form ula (30) cannot be derived on b a sis of a th eory A (see p art I). 5. M iscellaneous applications The scope and significance of the tran sform ation form ulae are no doubt m ost read ily ap p reciated if w e an aly se the m a them atical and p h ysical consequences fo r other field quantities, which can be derived from the fundam ental set E, B, D and H. L e t us sta r t with polarization P and m agnetization M. A coherent definition of these quantities su ggests th at ( P ; D ) and ( M ; H ) have pairw ise the sam e dimension. The follow ing definitions sa tisfy this requirem ent: dcf def B P = D e E ; M = - H (31) o fj, o The definitions (31) togeth er with the 'tran sform ation s lead to the follow ing tran sform ation rules fo r P and M : P ' = P EjLLV X M 0 (32) M ' = M + v X P U sin g the eq u atio n s (12, 13, 14, 17, 18, 19 an d 32) the fo l low ing sc a la rs (or densities) can be found having the p ro p erty of tran slatio n al invariance : E '. B' = E. B (33) D. H' = D.H (34) P'. M = P. M (35)

48 316 E. J. Post E. D' - H. B = E. D - H. B = Z, (36) E \ P' + M '. B = E. P + M. B = Z s '. A' q' 9' = s. A g cp = Z m It is a known, m atter independent p ro p erty, of electrom agnetic w ave motion th at E I B and D ih. E q u ation s (33) and (34) claim this to be true (as a first-order effect) for moving m atter a s well. Sim ilar con siderations ap p ly to (35). The expression (36) is the L agran g ean of the electrom agnetic fie ld ; it is due to its invariance th at the H am ilton in tegral dx dt d t time element dx = sp ace elem ent has an invariant meaning. E quation s (37) give the expressio n s for other L agran g ean densities L\\ and Z,ni which are relate d to the forces exerted on m atter. They d isap p ear, identically, in em pty space. In a lin ear medium E = \ (E. D + H. B) (39) is an adequate and allow ab le definition of energy density and def = - { ( E.D + H. B)I + ED + HB *) (40) defines M ax w ell s tensor of "electro-m agn etic str e ss in m atter It should be noted th at 55 is not n ecessarily sym m etric if (E; D) or (H; B) h ave different directions (an isotropy). E n ergy tran sp o rt S and momentum G are defined by the usual equations : def S = E X H (41) def G = D X B (42) The tran sform ation s of the sta te quantities and the definitions (39)... (42) lead to the follow ing tran form ation s of E, S and G 1) The sym bol I stan d s fo r the unit d y ad ic, and the d o tless ju x ta position o f tw o vectors (e.g E D ) stan d s for G ib b s d y ad ic product. The dot m ultiplication o f a vector into a d y ad ic (ten so r) (e.g. v. E D ) gives anothor vector. In gen eral v? ). v, i.e.? > is asym m etric.

49 Electromagnetic Theory of Moving Matter II 317 E = E v. G ejuv. S o o (43) S ' = S \ E v. 55 (44) G ' = G - sjuv E - e/i^d. v (45) 0 0 o o The tran sform ation s (43), (44) and (45) are p erfectly general, independent of the nature of m atter, in accordance with rule ( I I I ) of the introduction. The condition of linearity has been im posed to sim plify the physical in terpretation s of the quantities defined by (39) and (40). P lease note th at the velocity v ap p e ars a s a p refacto r of 5> in (44) but a s a p o stfacto r of 5 in (45). This m eans th at the as3rmmetry in anisotropic m atter is a calculation al featu re in the tran sform ation s of energy tra n s port and momentum. The p h ysical significance of (43), (44) and (45) m ay be more readily appreciated by the follow ing applications. The vectors S and S give the rate a t which energy is a b sorbed per unit a re a and unit time on absorbin g screens having a m utual velocity v. There are [two contributions which account for the difference betw een S and S ; v E is the extra absorbtion due to the tran slatio n al motion of the screen and v. represen ts the rate of w ork perform ed by the rad iation forces (radiation pressu re). In a pure w avefield the time av erage of the Poynting V ector S can be expressed in term s of the p aram eters of the w avefield : S = E g- g = group or en ergy velocity (46) In a m oving body w e ex p ect S' = E ' g ', (47) and g should be co rrelated to g according to the general fo r m ula o f F izeau convection. Th is can be verified indeed, if we use the w ave expressions for G and 5> corresponding to (46) and (47) for S. They a r e : E = energy density k = w ave vector co = circular frequency g = group velocity U sin g (47) together w ith (43) and (44), and substituting the expression (48) and (49) fo r G and < > w e o b tain :

50 318 E. J. Post S' E g E w v. kgii/co g v v. k g/co ^ E E v. k E/co ejuv. g E i - v. k/a> e/u v. g 0 0 o o This gives the first-order expression : g=g-v+ /iv.gg, (50) o o which is identical to the first-order resu lt obtained by m eans of the relativ istic theorem of velocity addition for a rb itra ry directions of v and g (ref. (2) p273). A ppendix I There are tw o contributions to the to tal time derivative of a su rface integral. O ne is due to the intrinsic time dependence o f the v e cto r field A, the oth er is due to the change o f p o sition of the surface w ith resp ect to the coordinate system. This lead s to the definition form ula : d dt A. d o = da Lim I A. d o I A. d o 0/ -d a + A t ^ o ~ a 1 I o ' The second term in the righ t hand mem ber can be calcu lated using G a u sz theorem fo r the cylindrical volume gen erated by the motion of the su rface (see figure 1). K eepin g in mind th at the vectors do' and do are pointing in the sam e direction, G au ss' law applied to the volume of figure 1 gives : Tim e differentation o f a su rface integral A t j (div A ) v. d o = j A. d o' j A. d o + A t J A. d X v II The la s t in tegral can be tran sform ed according to a w ell known vector r u le : A. ^ X v = - A X v. d = - / curl (A X v). d o, the tran sform ation into a su rface in tegral is done by m eans ol S to k es' theorem. Su bstitu tion in II and rearran gem en t of term s y ie ld s :

51 Electromagnetic Theory of Moving Matter II 319 j A '/< t / { v div A + curl A X v }. ^ = \. d o j A. I I I Su b stitu tin g I I I in I gives the d esired form ula. or -{-[curl (A X v) 4- v A 1 i d a I V A sim ilar form ula can be derived fo r a volume in tegral ƒ gdx. T akin g g = div B, ƒ g d x = ƒ B. d o. The form ula can be applied to obtain the time derivative of this in tegral over a closed su r face a. Then w e o b tain : rem em bering div curl O. The case of a line in tegral cannot be derived from form ula I V in an unique w ay. A sim ilar an aly sis, how ever, gives (see ref. (2) p i 29). d dt A.d % v X curl A + g r a d v.. d \ V I The equation s IV, V and V I are sp ecial cases of a more general theorem : L e t the integral V have an in varian t meaning. The field 0 is, except for an explicit time dependence, m oreover su b je cte d to a d eform ation, d e fined by the vector field v d t, then the time derivative of ip is i The sym bol stan d s for a sim ultaneous d eferen tial invari- V an t of 0 and v, known a s the L ie derivative (see ref. 3, ch apter II, 10, and p. I l l problem II 10, 11). A ppendix I I The re is a fundam ental m athem atical difference betw een the linear vector function e relatin g E and D and the linear vector

52 320 E. J. Post function 7 relatin g D and H. The difference is cau sed by a m athem atical distinction betw een the electric and m agnetic field quantities. The simple physical devices of a p air of opposite point ch arges and a coil w inding w ith current, which generate an electric and a m agnetic field, respectively, em phasize alread y strongly the different nature of the tw o kinds of fields. The m entioned distinction is usually of no consequence unless one in vestigates tran sform ation behaviour with resp ect to im proper ro tatio n s (properties of m irror sym m etry). The conventional notation of vector an aly sis does not account fo r this diiference in behaviour. M ath em atically it implies th at the m agnetic fields are b etter represen ted by bivector quantities. The bivector can be regard ed as the vector product of tw o ordinary vectors. The cu stom ary procedure in vector algeb ra, to identify the resu lt of this operation w ith an ordin ary vector, is correct, only if coordinate system s are considered which are m utually related by proper rotation s. An inversion is a w ell known exam ple of an im proper r o ta tion. The inversion reverses the positive directions of the coorordinate axes of a system of reference. This im plies th at the three com ponents of a vector change their sign, if the coordinate system is subjected to an inversion. R ecallin g the exam ple of the vector-product, it w ill be clear th at the com ponents of a ^ vector are not affected if the system of reference is subjected to an inversion. H ence the consequences of an inversion for the equation of state of T ellegen s medium (2d) a r e : D = - E + 7 H B = - 7 E + /.H A pplying N eum ann s principle, this equation should be identical to the o rigin al one (24) if the medium is su p p o sed to be iso tropic. The resu lt of the identification is 7 = 0, w h ereas e and /u are allow ed to have arb itra ry valu es different from zero. The distinction betw een the linear vector functions and /x on the one hand and 7 on the other is know n in ten sor an a ly sis a s the difference betw een a ten sor and a pseudo- or W - tensor. A recent text ab o u t this su bject (ref. 4, p. 159) gives the inform ation required about the possible existence of a gyroscopic effect (W -ten so r) on b a sis of N eum ann s principle for an y of the 32 cry sta l classes.

53 Electromagnetic Theory of Moving Matter II 321 Conclusion an d Acknoivledgement A sem i-classical ap proach dispensing w ith the concept of aeth er h as been given by P ro fe sso r E. G. C ullw ick in his book : Fundam en tals of E lectrom agn etism " (5). The presen t p ap er gives an attem pt to extend this ^point of view to the specific field o f m oving m atter. The auth or is indebted to P ro fe sso r C ullw ick fo r am ple and stim ulating correspondence and to P ro fesso r J. P. Schouten and M r. L. A. W. van der L ek fo r m any helpful and valu able discussions. References 1. T e 11 e g e n, B. D. H., Philips R es. R eports 3 (1948) p. 81. T e 11 e g e n, B. D. H., Tijdschrift Nederlands Radiogenootschap, 13 (1948) p. 73 (dutch). 2. M a d elung, E., M athematical T ools for the Physicist, Berlin N ew York, Schouten, J. A., Ricci Calculus, Berlin London N ew York, Schouten, J. A., Tensor A nalysis for Physicists, O xford, Cullwick, E. G., The Fundamentals of Electromagnetism, Cambridge U niversity press, 1949.

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55 323 N IE U W E U IT G A V EN D e redactie ontving de volgende nieuwe uitgaven: Electronenbuizen voor batterijontvangers door E. Rodenhuis. V an microfoon tot oor, door G. Slot. Gegevens en schakelingen van ontvang - en versterkerbuizen, deel 3B. door N. S. M arkus en J. Vink. Vacuum V alv es in Pulse Technique, door P. A. Neeteson. In een der volgende nummers zullen deze uitgaven besproken worden. Boekbesprekingen Second Thoughts on Radio Theory door Cathode R ay of W ireless W orld". U itgegeven door Iliffe and Sons, London biz., 15 x 22 cm. Prijs 25 sh. Reeds jaren lang verschijnen in W ireless W orld regelm atig artikelen, ondertekend met de schuilnaam,,cathode R a y, waarin allerlei onderwerpen op radiogebied op bevattelijke wijze worden besproken; het is daarbij de bedoeling van de schrijver om te laten zien dat ook in vrij elementaire onderwerpen bij nader inzien bijna steeds meer in zit dan men wel gedacht had. V andaar de titel,,second Thoughts on Radio Theory van dit onlangs verschenen boek, waarin om streeks 40 van die artikeltjes uit W m eless W orld, w at bijgewerkt en gemoderniseerd, zijn sam engevoegd. D oor de heldere en vaak geestige wijze w aarop de kwesties gesteld en besproken worden, zullen alle geïnteresseerden op radiogebied ook de meer ingewijden met genoegen dit boek lezen. E. O. Radiobuizen Vademecum, door Dr. J. A. Gijsen. Uitgegeven door P. H. Brans, Antwerpen, 12de uitgave, 381 p ag., 20,5 x 29 cm. Z oals bekend is het Buizen-Vademecum dat geregeld door de uitgeverij Brans te Antwerpen wordt uitgegeven sedert 1952 gesplitst in drie delen. De negende uitgave die in dat jaar verscheen w as uitsluitend aan zend- en ontvangbuizen gewijd. De 10de uitgave (1953) behandelde vervangingsbuizen en in 1954 werd de trilogie voltooid met de 11de uitgave, welke Televisie- en speciale buizen behandelt. T h an s ontvingen wij de 12de uitgave, een herziening van het in 1952 verschenen 1ste deel: Zend- en ontvangbuizen. Het voorwoord vermeldt dat men de gegevens van een aantal oudere buizen heeft laten vervallen. Uit het feit dat b.v. van de oude Philips A en B series nog tal van buizen zijn opgenomen moge blijken dat ook degenen die gegevens van verouderde buizen zoeken deze v aak ook in de nieuwe uitgave nog kunnen vinden. O ngetw ijfeld zullen velen zich het nieuwe werk aanschaffen gezien het aan tal nieuwe zend- en ontvangbuizen dat in de laatste drie jaren aan de markt verschenen is. H.

56 324 Uit hei N ederlands Radiogenooischap V E R G A D E R IN G E N Sinds het verschijnen van het vorige nummer had op 17 O ctober te H ilversum een vergadering plaats waarbij als sprekers optraden Ir K. Rodenhuis met als onderwerp: Levensduur en betrouw baarheid van radiobuizen voor professionele toepassingen, en D r Ir A. van W eel over het onderwerp: Fazelineariteit v an televisieontvangers. V O O R G E ST E LD E L E D E N G. Gaikhorst, C oosje Buskenstraat 32, Vlissingen. (P Z E M, M iddelburg) Ir L. Krul, Jan M aetsuyckerstraat 63, Den H aag. ( P T T ) C. A. vsmit, Sandenburgstraat 194, Den H aag. (P T T ) N IE U W E A D R E S S E N VAN L E D E N Ir M. P. Breedveld, p/a Thierensw eg 13, N aarden. R. Y. D rost, Rembr. v. R ijnstraat 73, W eesp. Ir J. A. Hammer, K oepelw eg 30, N oordw ijk a/z. D r Ir E. W. van Heuven, p/a N.V. Philips Gloeilampenfabrieken, Lichtgroep, Eindhoven. Ir J. A. K oster, Leenderw eg 319, Eindhoven. Ir J. J. Schreuders, H ofbrouckerlaan 22, O egstgeest. Ir C. J. H. A. Staal, B oerhavelaan 57, Eindhoven. Ir M. Steffelaar, Jonckbloetlaan 13, Eindhoven. Ir J. D. H. v. d. T oorn, V a n B ergenlaan 4, W asse n aar. Ir L. R. M. V o s de W ael, L aan van O ostenburg 49, V oorburg. Ir A. W ieberdink, van Sw ietenlaan 10, Eindhoven. Ir M. Ziegler, c/o Philips Chilena S.A. de Productos Electricos, Casille 2687, S an tiago de Chile (C h ili). O U DE N U M M E R S G EV R A A G D Een onzer leden mist van deel 10 het vierde nummer en van deel 11 het eerste nummer. D egene die deze nummers af zou kunnen staan w ordt vriendelijk verzocht zich met de hoofdredacteur in verbinding te stellen.