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RESEARCH DEP A;RTMENT

NORWICH AREA SITE TESTING

Report No. K.065 Serial No. "1946/1

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Researoh Depart,nent

work done by:; ..... ., . L .F~ . T'aghciJJii. .~d' .

C -l? .' 'geoghegan . ',"

in qonjUriction wi.th . . S .B .' (T) 's J;)epartmen t'~ '.

REPORT NO. K.065

.' Serial"'U6 .'124$4,'., " ..

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NORWICH .AREA SITE TESTING , .. "';' ~'. . .... '

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February, 1946.:.

'·:·F~g. Nos.·.1 - '4~

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INTRODUCTION' . . ::, \ '. . ,,' :.,.,; ; ..

e. I,: ' .. It' was.',prbposed in '19~9 t6 ~!)V~de it relay station fo~, -&h~ ~6r:w.ich ,fl.ist.~.Qt~.··~ 1v:qicn woul~ ~rk on a wavelength of about 215 metres, with a power of about . '. ;15 ·lCW.;P<\)Fls~:9J.esitesfQr suoh a..transIpi.tter we,red.escrib$d i.nResearcl:J. . Report . :No. K.050,):re~ia;L.No.1939/17~ dated 15th JliIUe, 1939 ~" 'It waS' not at that t:iJne p;'oposed to test sites in .the I'egion as i i;;was thought that; this:part of East . ~glia:hada uniforinlygoodground :conductivi ty •. ', Our experience and. , measurements made during the vyar ·.showed1 hOV{eYer,; .. 'th.at the ·~ound. conductivity ID the region. to .~~ .,~~,l:\.t.and north of NorWich is variable, being good over the alluvial.soil: ill the . "BroadS" di'stnctan.d: rather pOor' in other. regions where' there are sand

•. ; Md' gravel depositi.' . ..... . ". .. '.' . '. '. . ! "" I,' " "

.' ]i'(i.'the ,pOS t-Warseririce t'o' ~hi's : ar~ . i;t "is' ,proposed 'to provide .• atfw~ . mi tter ot ··~oW. PoWersY:n,chronised ,either.: w:i;th D.roi twicl:ron'29tm or with .. Broola.\l~ Par.~qo.,34fm~. ";'This"change;!'rom the ·19'39·poiiCy .. i~volved the. selec.~ion of the oos'tpossible ' site forprovidinga~service to :at least NorWioh, Yarmouth and Lowestoi't:under the condi ti0!1:s Of. synchronised working .. ,

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;' .' .A ~it,~.~t·Thorpe wa.s sele.cteq.by S.E.(T),tg ,Departm!3nt as:a' replacement. for the exifiting :,vatt;iJn,e,site at Caley'~wOrks:in·th~cel:ltre, of.Norwich., . This site is close';toNorWichand would clearly provide a site suitable for serving NorWich only:~,al~hpughthe geological subsoil of sand and gr-avel caused doubts of tqe ..... ~ .. : aeria,lefficiency ,ana. local attenuation we would be likely to realise at this 'site. Two alternative sit~s·'were found aft~:r;,' disoussion with Research Department, ;Which were expeoted 1:;0 give a.1:Set:te+, serVice 'in. Lov{.estoft.and Yaim'Ouththanthe' .Thorpe site.'. These.si tes' w~~e· at Bra.merton, •. abput:£i 'tie miles sou~l'),-east Of the centre ofN'orwicll"a:ndat thePostwick Cross Roads, about four and a half miles due east of the'ceritre·:of. NOr.vich on the main road. to Acle and Yarmouth., It was required to com:ple-e~.tl1e',si.te t~stingin th~ minimum.:time. possiblei. and., it was, therefore, necessary. toc~j:~tail:.the.riJ.easUrement work as much . :as. possi bie~' :.' The,. posi i;~OIB .of the~hree·:s~:tys;.·a.reshovm9nFig~4,. whJ.qh .:fs .a map 'reproduced 'from tne Ordnance SurVeYlj#.I':s~pes •.. ··.·At/t'\}.e .. time t.he tes.ts:,yi~:re.carried, out, it waS' expee;,ted that th.E;sft~·Yi~U:lc1.· be r~'g.llired-tor ra(iiating'-Fl1e IIAII ProgI-?llllll8 .:ori29.6.~;';1013 kc/s, and the.;llbl';Pro~_;·.,q:n.267~:?nl;.i122·.,kC/s.l: . Tests were,.jiijerefore, ,c.arrled out on a

". . '., . ... . " " . ,·r .~;" .. " ..... , ~ . >,~ , •• ' ,c" . • <. , ..", " :.. '.' ~'" ,_ _ :..".. ••

.'( > "~.2::' .,<~'t.'':'' -:,;:,: '.~ ,.~~ :. ,.:,': ,~~: ." : 1''<:' ... ;.:;" .. .t,' t; ,':':, .'. ", .,'

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, frequency of 1063'kC/s,wbich 'is ,apptox:UJlately the frequency on which the field, , strength would have"the mean value, fof,~ s?-y,~ 'power, of that on 1013 or 1122, kc/a .. The field 'strengths which will be obtained will be about 10 - 15% higher on:296m than the test values and about 10 - 15% lower on 267m. '

METHOD OF TESTS r , '

< r\I. A mob~le transmitter of~l:>o~t ,g.50" :wat'tsqut.p.p~. power was used~ and ~n.'~~,o~l~!gf " the three s~tes tested was fed into an aerial and earth system' of exactly s:unJ.liijtf' dimensions. 'Measurements on an R.F. bridge of the aerial series impeaance:'at:;.I(l,;;";

, each site gave a oomparisonofthe aerial efficiency, and thus anmdicatfbp.'o:f',' e theliltelihood ,of obtaining a permanent aerial' :aysteirf of reasonably hi~. e:f'fici~ncy.

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At each si te the field a trength measuz:ments takeri. were as follows:

'(a) Polar diagram at 51~n radius.

Cb) Atten~tiop. runs invariousd{rections.

,,(~) IISpot" readings in Norwioh, Yarmouth and Lowe~;toft~, ",

",' The polar diagrmns were measured to check the presence ~f ~y high local <:,-tWri.Uatiori,~n;anydirectiori,from either site. The a~rial,sys,tem usEld. ,for the test was pf .an, omnidirectional type; any distortion of, ,: the polar diagram will be due to'lp~al attenUation. 'Detail's'of the test aerial are given iIj, 'the Appendix.

The atte~uation runs' were made to enableoontours of field strength tabe subsequently plotted if required" Without further comprehensive measurements, , from the ai te finally selected. 'J '

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The "spot"rea:dings were take~at '~elected poin,ts, iri.the three t, Owns, , and chosen so as to pe representative of urban and suburban listeniilg areas.

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RESULTS'

Figs. 1, 2 and 3 arethe.~lan po1ru: diagr~of the Bramerton, Thorpe 'and Postwick sites respectively t' ' 'They show little distortion from any 'one of these. sites, and all, ~thTee si tea may be, consi~ered, to be satisfactory "from this point

, ot', view. ' , , ',' : """, :' ,", "';'" ' .',' ',.' '

.: Th~attenua.tion runs ai-e,not; ;t;'eproduced her~, ~ theyhav~ n~,'imniediate bearing on' the selectioi:l of a su:i.t~1:l:Le' si t,e. ' ,

, 'Ta,bie ':rgives the field:,~,~re~gtp. results in'the form in whidhthey are most use:f\ll for c dmparis on purposes ",in the· selection of:,the best: site'. It will be, ' seen that th~ Tb.orpesi te (B'~'givesa high field streAgth .in Norwich, but does not give such a goo(i field strength in Lowestoft or 'Yarmouth as either" Bramerton or Postwick. The Bramerton'site (A) ana. the Postwicksite (0) give about the same ,

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field stre!).gth in Yann.)uth,butPostvvi;ck isdefini;tely better in both Norwich ~ Lowestoft than Bramerton.Th~ ,~ostwick site is,; therefore, the bes!t for an adeql.late service to NOIWich ,and for ,as goog: a' service as possible to both Yarmouth 'cmd Lowestoft.

Table II shows the differeh,c~'in > aerialimped8nce on the three sites using the same standard aerial and earth system at each site.

, ,," "It will be seen that the totaiserie~ resistance of the aeriaJ, system is only 9.9 ohms at Pos:tvvick,as against about 14.5 ohms at both'Bramerton and Thorpe. The, e calculated, :radiation resistance 6f,the aerial system used (see Appendix for '. " dimensions) is ,2.1 oms" so that, the "deadlosstl resistance of the aerial system is' ,about 7.8 ohms atPostwick and 12~46hnis at .. , ,Bramerton, arldThorpe~ The Post-wick site is :thus tM"pes~.f'Qr' local losses as 'well" as for field strength obtained in the service area. The difference in the tldead loss" resistance would not be signific'ant in determming the effipiency of the aerial system eventually used for this station, unless we were obliged to use low masts and a consequent low radiation resistance.

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Of the :three sites tes.t,ed, Post:wick is ,the,most sui table for synchronised working., ·A2 kVf transmitter,synchronised onl0l3kc/s ,with Droi tWich, will ,provide average -field strengths of about 34, 11. and '7 mY/m in Norwich,Yartnouth and Lowestoft respectively.' )

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eRAR/IX]i . . ~ .

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!.ABLE I

(X ~ 282 metres,f = 1063 kC/s)

Site A= Bramerlon

site B'=Thorpe

Site C = Postwick,

The more important fi~e'S are underlined. "

r'~'~ 'i M-'E e-a~~-·e"""'d~F-ie-l-d-s"-t-r-en-g-t-h ........ r-r-F-i-e~d ~'tre~gth--l -Field strength " , from .' vr.ith . with

I ,I Measuring

Post. j .Mobile Transmitter. 1 kW Transmitter. 2 kW Transmitter. I (Go%) ( 60%)'\ .site Site Site site Site Site I ',Site, Site' Site I 'A B·' CiA , B cl AB' C h __ ~~~,~! ____ ~~----rl--~i~l~--._.--~~~--_r,--

11 6.4 63 -I' 10.7 I 25 I fforwich, East. , Centre.

West. I i 5 19 8. 21 19, ' ! i 3 8 , . 3. 7: ' 12 ' ,I I

260 80 33

Average of 6 po:Lp.ts. 11 !±:2.-1 I •

I i ,22 - &.:2.: . 17. 2 .2,g,

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Yarmouth, North. '/: I', '2;.22 Oentre. '

I • South. 1/1.,7 It Average of ;-I '7 points. 11 b2.2. i H

1.3 \ 1.3 1

I,g I

2.4 I . 8~5 2~3 I 8.5 1.51

1

6.6

1 M I ; ! Lowestoft" North. ,'1.4 0.8 · 1.2 ,5.4 i Centre. 1.45 0.7 1.2 ·4.8 I south. I 1 , 0.7 1.7" 3.9

5.4 5.4 4.2

40 31 14

, 24

9 8.6 5.6

4.5 4.5 6.4

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35 27 17

62.

370 110 47

130

57 43 20

2!t.

12 7.7 13 12 ' 7.7 12 9.5 5.9 8

1:1 7.1 1Q.:.2

7.7 6.8 5.5

6.3 6.3 9

I' Average of . Ij

1= __ 5, PO::_ •.... _ .. , _1 __ ~· ...... lj ____ '....l-_0_·._Z6_ . .....,;1_1_.

4_ . .w..11_, ~_,_4i"--.---.J"----;-.1-I..L __ .;,.,.,..-.--,-"------,.-,0,.

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TABLE II'

Site

A

B

C

'.,

NORWICH AREA SITE TESTING

:lQ4$ .

Base·' -Bramerton

Thorpe·· ..

Postwick,· .

....... -..... ---..... ---~-.....:.~.

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. Aerial Im.2f'dance

14.6- j382

14.5. - J380

9.9-j394

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!'J9RWICHAREA SITE TESTING .

.APPENDIX I

p~ai-ls . of. ,T..?st· Aerial and Earth SystemS

T. aerial supported on tubular masts.

." Mast spacing _ ... - -'-' - - - ~

45 feet

130 feet

Length of aerial top hamper -- - - - - - - 120 feet

Length of aerial dcr~-lead ~.- - - - - ~ ~ 37 feet

Length of wires. of r~dial earth, sys tem, each 100 feet . ..,'

Number of wires in radial earth sys tem 8

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.APPENDIX I1

" Geo graphi9J~;;L Posi tionof Sites

Name of Site: ApprOXimate position:

Lat. i

Long~ . ,Grid reference: Ordnance Survey Map, .6 11

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(Norfolk) . Ordnance Survey Map, 25 11

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(Norfolk) . Land parcel No. on 25" '

map:

Branierton, 5 miles S .E.·

NorWich Cathedral 52 35 09 N 01'23 38 E G 756222

LXXVI.N.W.

. LXXVI. 6

Part of ,172

., Trrpe" 1'2' miles' E.

Norwich Cathedral , 52 3753 N

01 20 10 E G.715270

LXIII.S.E.

LXIII.12·

Part of 88

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Postwick 1 · ,

. (

'4~ miles, E. . Norwich Cathedral

52 37 35 N 01 :24 15 E G 761266

LXIV.S.W.

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LXIV~lO and LXIV .14

Part of. 99,

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DATA SkEET No 13. CIRCUl.AR (POUR C~ATE.

This specification is the property of the • BRITISH BROADCASTING rORPORATION, and may not be repl-oduced or disclosed to a third party in any form without the w ritten p ermiSSion of the CorporatIon.

~WIGHTMA.N MOUNTAIN LTO ART'LL£R _ E . ARTILLERY Row. WESTMINSTER. S.\V. l .

tts.

DATA SHEET Nn 'l '-.IAC"\.J..A P'o ~Il Co.. NATE

This spfl:::ification is the property of the 8:1 IT::::H BROADCASTII'JG CORPORATIO N, and may not be reproduced or disclosed to a third party in any form without the written permisSion of the Corporatlo,!!

__ WU.~""'MAN Mt)UNr~IN I TO

ARTIL.LER..,..C ARTn L'-~r POW. WE'STftro.1IN5Titft . 5 W.1.

•

DA"To\ 'iHlfrT No 13 ~ CIRCUL...An ( POLA~ j C~nOI"' ''''L

~h·S sp"!cification is the property of the :J11T13H 8RC)ADCASTI~,G CORPORATION, 3~cJ may not be reproduced or disclosed to a third P3rty In any form without the written.

WI~HTM"" MOUNTo\.I"-; L Tf"I AFtTIt..LEt.r'( HOUSF, A~nll rF(v Row \I\ol.-.rYINS'TE,R c:, \y 1

perm's_s_' __ on __ o~the corporatlon~~~~~~~~~-r~~~~_~~~~~~~~~~~~::~i'~~:-~:-;r~~~-:~~~;:~~ __ ~::~ ________ __ Q I'

/ /

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ORWIClI AREA S ITE TE~TING.

Fig.' 4.

Report No. S ... i.1 No.

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