Spectrum Analyzer for VHF/UHF AmateursConstructing a Home-Made UniversalHF-Module

•

by E. Berber iCh, DL B ZX

The description 01 th e 11'11 apecl rum ena "lyle, , t th e VHF·UH F Convenl lo n 1976 inMunich, end In VHF COMMUNICATIONShtd to • la rge num ber of I,n, r, 'r om Ime ·leur, th el wi,he d 10 COO"'ut! s uc h •spectrum 1 "11y" " Unlor1u"e 'e" . th, con­struc tion d,"iCuttl. ' wilh r••pect to theAF·j"pul module , end the , me n It.qul ncyrlngl:' 01 the lir.t ve" lon we'. not r••lIyab le 10 ..Usty th e dem and s th ll w.,.pl aced on It. The dlveiopme"t and con­, truc ll on 01 • sull able RF·lnpul module I,•• Irem '" d iNlcult tor redio emltlur. th. ,do nOI h .",. I CCI . I 10 • ' erg. I mo unl 0 1• • pe nal ve me••uting equipme nt (QAL).For thl , , ••ton, I " " eence pucn we .

d l ve lo pe d th aI Un be r• • lIze d lol ling con.vI"lion,1 module. a"d eompo"e"I• . Thl." ew de. lg" we. de.erl~d . l lhe VHF·UHFCcmlle " lio" 1980 I" Mu" leh 8" d I. "OW 10be de. er ibed '" Ih'. 8111(;Je.

I . METH OD OF REALI ZIN G THIS AIM

In orde l to d isplay a Wide frequency I<m911at one tim e, It IS necessary to use a hll:,lhI lf st mt errn eo.ere treq uency (IF) and anOSCillato r that can be swep t electronicallyover a correspondmgly Wide range Thereare several possibilities 01 aVOiding co n­st eucncn 01 these entreat modules

111 IF

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101m.. . .

•r*o-l~_0. kl).l6:X! l,l f<l

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DL 8 ZX

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, 1.1. U•• er Industr .a' RF·Modu l..

Comp le te "ng muers lor 50 U ,U lI availableon Ihe markef thaI can be us.ed up 10 veryhigh uequences VCO-modules a,e al,oavailable lor the VHF to SHF range ThereQUired hlgh ·pa SS and low-pass I llIerl . aswell as calibrated allenualoll are alsoavaIlable I rom well -known companies Fig. tshows the use 01 suc h compo nent, ,n con­junction with a spectrum analyzer IS A,IThe only , bullmporlanl d isadvantage 'I thepri ce 01 these modules. whi ch " usu ally larmore than IS aveuetne lor one I hobby

1.2. U• • 0'. Cab le -TV·Tuner

Special luners are manulachHod 101 cableteleVISIOn (CATV) tha I can be Tuned co eu­nuously n om 40 10 300 MHz and ooe reteWith a l ' fsllF ot 600 MHI CATV ·luners alsohave good large-signal hand lmg capablli­l ies

Flgur. 2 glvH the block diagram or a spec­l rum analyzel uSing a CATY ·Tuner Th iS SAcan co ver the Irequency range 01 0 1 10 40MHz, and 40 10 300 MHI In lwO swllchablebands Howevel. It IS nol easy to ob tamsuch tuners Irom lhe servi ce departmen t orme TV·manulacturers, or CA TY·companles,presumably, because they think one Wishesto lap mtc lhelr cable syslem Without poly·mg the monthly lees I FOI lhl S reason. ui eaumor allempled 10 fmd a furlher soluil on10 me problem

1.3. UHF-TV ·Tuner •• Tun able Flr ltIF · ...mplifler

A spectrum analyzer can also be realizeduSing a UHF-lunel Irom a TV·lece,velSmce It IS to be used In a measuring sys·lem haVing a hIgh dynam.c range , a TY·nmer should be round haVing lalge·slgnalhandhng capabili ties , tnar do es no t use ase ll-e llci led ml.er A Iur tne r advan tagewould be 8 lunab le Inpul Circui t and a 75 ~J

IF·outpul

As lar as lhe autho' knows . no separateUHF· tuner ISmanulactured In Germany . bulhe lound it SUitable rcoer tn a Japanese TV·recei ver Th.s used a UHF-tuner uSingmerar-ptate chambers WI!tl tunable InputS1age . as well as possessing a separaleosclilalor and diOde rtuxer ThiS lunti r IS

readi ly avai lable In Germany " om lhe ser ­vice departmen ts 01 lhe targest man-orderco mpa ny

For those reade rs tnet ere not able toobtain such a luner. II IS pOSSible Ina t lhlscould be obta.ned lo r you In Germany allOw cost

Figure 3 shows the I ,nal SOlution rn thelorm 01 a block diagram In order 10 aVOIdespenerve ccacer ewncnee. each rrequencyba nd possesses ItS own mpu t connec to rThe range SWllchmg IS made al the mput 01Ihe l une r w llh me aid 01 PIN-d iodes Ino rde r 10 coram a constan t sensitivi ty ove,the wh ol e lumng range . the lu ner mu slhave a slightly , lop ing freq uency response

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DL 8 ZX

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f--FiC-': ,f -.q ,..., ,.. -_ ~

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The me8sl,lflng accuracy IS mainly deter ­mmed by thlll characle"S!IC

As can be seen tn the block diagram. threefrequency range s 01 apprO~ lmalely 400MHz eacf are obtamed In a Simp le mannerA lower band from appro.,malel)' I MHz(lower cu i-oil frequency 01 'he ml.-ar usea lto 400 MHz (I). the dlrecl tuning range 01tne tu ner 'rom approxImately 430 to SOOMH z (II) . and IInall y an upper band (UI) re­pr esenting Ihe Image frOQuency 01 thelower band , WhiCh covers Irom 1230 to1600 M Hz

Of course, an UHF-SHF-conslruclOfS '0'1' ,11have noticed lha l the mos t ImpOrtan t fre­quency ran~ In me orde r Of 11500 MHZ.w h iCh IS used as ioce t-osc-uaror freQuencyto r vl rl uaUy au rruercwave amateur band s,IS nOI co vered For thi S reason me 800MHz OSCillator IS des Igned to be lunableIrom 710 10 800 MHz ThIS meanllhat II IIpossible 10 sh, tl me Irequency range scree­wh at w hen the meer IS used (preml,,-oper ­atlon) Th IS hrsl loca l c sc.uercr cou ld be10C~ed to a 72 MHz crystal OSCl ll l to r usmoa PLL -ClrCVlt In cor uuncnon With a ewac n ­able diVIder (by ten or by eleven ) II narrow-

FIg. 4: Fr.qu.ney pl.n lor Ih. Iln. 1, pKlrum .n.'yl" . hown In 1''9 - 3

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2030 ''00

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FIQ. ! :" to-.p... f ln., !Of' ""fe IL 1 • L 01 , .ectl)S """ 10",. fOO U ,tropHne_....,f.c:lllled by M,,,_nl

• band ' ,lie,. are used ,n the I,'s ' If IheMmeuur•• • r. absoluTely neceuary te••uP­p,eumg ,,,. Inter1ereoce dev.ahon

Figur. .. ahowI .. frequenCy pia'" whIc hallowa tw o further ' reQlAflCY r.no_ 10 Moblaone<! USIng .. leCond lOcal OSCillaTorTheM renoes IIV) ancl (V) na~e It,ll notbeen reah zed by Ine au thOr

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2. THE FINAL CIRCUIT '~-----..

As "as .I'~ been menllOl"eCl !hI' IP« ­' rum " 10 be constructed as g'ven ,n Fog 3Furthe r det,lllia are no w 10 be g,ven regard_Ing ....11101,11 modules

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OlB ZX

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Fig. • :Ctl.,ect.,lltlCof II'Ie to- .ea-"I,n., II'''.'' In Fig. 5

0 1 COY''', these "al"," a l. only p.nenlwhen th e s trlph".. a re glued to • me l,,1l urface The 100 U line was telected lo rthe 10w· pllSl hne , ,n Older 10 Obta,n thesmallest poas'ble ConSIIUCI,on The _s­Uled a nenuallOn Curve ISg,yen In Figul. S.

.. 7 nH78 nH

6011100 U

The IOW-Pd!lS utter to, 450 MHz " con­Ilrueted tn a metal·plale case 01 37 mm •111 mm The mduc tances (FI';IUf. 5) conillto lIO-called Z-ll rtpS manu faclured by M,ni ­mou nt These sell-adnes,Ye epo.y-glasa' ,br. S",PI w,lh co pper coa ling ar. 01"0111 ­

able ,n apprournlI lely 100 mm length 101the ....nCu. lITlpec:lancn (SO U . 60 U 75 U ,and 100 Ul Defined 'nductances can bemanufaClured USIng theM , trops and ItltItanow,ng Inductance va''''" ......e'. calcula,­ed lor Ihe varlOOS "r,pl'ne w,dthS t,mpe­dane")

50u 39nH.7SU S8 nH

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Fif 7:P,....' .., mod"..with IHF 1111111......hn., ."d PIN ­diode ••llell

2.2. 1100 MHz Hlgh·P... Flll lr I nd MI.lr

The SHF hlgh ·pass I lll er. PIN·d,Ode SWitch .ring moer, and a 3 dB allenuator lor theIF-ou tput are combined as sho wn In Fig. 7to teem a Mpreml lerM mOdule The high·pass ind uc tances L 5 and L 6 have an m­euctence 01 4 nH and have been cons truct ­ed In pr mted technology

The arrangement c t the components IS verycri tical in this module II the crOSI- lal k be­

tween tne three channelS IS 10 be kept to alow value For this reason. • preml lfH 'board was developed that may be des­cribed la ter .

2.3. Ol clllator Moduli

The local OSCilla to r Ir equency 01 710 to 800MHz IS I lr stly generated In a ' ree·runnlngosc illator as shown In Figurl 8 The resc ­nen t ci rCUit Induc tance L 2 comprises a 3cm long p iece 01 15 mm d,a Iilver.platedco ppe r wire A verac tc e diOde type BB lOSIS co upled to thiS line and uS&d lor luning

The OSCillator drives «uc an apenOdlcbutler With feedback . and a 3-5Iage low·pass I ilter The fil le r IS construc ted In thesame manner as the Inpu t lo w· pass nuerfor fange l; Inductances L 7. L 8. and 1 9are a smgle piece 0 ' 100 U IInpline ontowhich the capacitors are soldered With aspacing 0 ' 17 mm each

2.4. IF·Amp' ifle r and Sel ectivity

The Inst IF 0139 MHz prOVided by lhe tunerIS too lo w 10 obtain a high Image rejec tionFor tt ns reason . the dynamiC range 01 lhe,nd,calo r was limited to 80 dB ThIS meansthat only 8 stages of tne hnearllogar,lhm, cIF·amp li fle r 018 ZX 000 (VHF COMMUNI­CATIONS 2/t9n) are used

In the case of the author's prototype, Itleccnversrcn to 10,7 MHz WIIS nOI ceee inorder to avolCf unw anl ed reception pointsWhen USing an op l,mum cceeeucncn.however. It IS posSible 'or double ccrwete­Ion 10 be eeanzeo satls 'actonly In order toImprove selechvlty The advanlages 01u eee measures were discussed In lhe pre­vio us pubtrcenon . as well as ,n (3)

In the case 01 the aulhors proto type, onlylhe selectiVity of the 39 MHZ-CirCUIts 15euecnve The rMultlng overa ll bandwld lh 01appro xrma tetv 600 kHz IS 100 WIde lornarrow- band displays Unfortunalely . nocomme rCially available crystal fil ters areknown for a 'r equency of 39 MHz. crys lalti llers are available lor 35 4 MHz I B 8kHz (Philips). 41 MHZ I B 7 kHz (Toyo ­com). bu t are too 'ar Irom lhe required Ire­quency 01 39 MHz

For th iS reason. the aultlor cal culaled andco ns tructed a helical bandpass 'liter for 39MHz lo r the prototype syslem Lcw-cepecr­ranee rela ys are used 10 , wl lch thiS f,tlermto tne Signal palh when feQUlred (Fig 31

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fig, a:An 800 MH t vee

221

fig . 9 shows one stage 01 the IF'3mpl, !,erDL 6 ZX 003 whIch has boon mod,ll~ rOf39 MHz Inductance L I coosete o t 11 turns01 04 mm d,a couon-co...e-ec. enamelledcopper wIre, wound on a 4 3 mm COil tor­mer wllh ViOlet core II the Inductances areenc losed In cans that are nol lao smatl, It ,spossibl e lo r the sc reening pane ls betweentne IndIVidual slages to be deleted

A shori descnpt,on 01 the IU'ea. llog8f1!h­rmc IF-ampli fIer '5 no w to be 9, ...on , amce IItorme the heart 01 the spec trum analyzer

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O. .... lopm. nl 01 In. IOll, ••,h ml(: se. "

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Dl. 8 ZX

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Fig , . :TtI.lf ' ''·II''01 modul.OL I Zl( 003• •• mod il l. d10. 311 MHI

In order to ob taIn a dB·hnear (In o therwor ds a logari thmiC) scale over a largedynarmc range, It IS poSSIble to use a so­ca lled succeYlve rec ti lier amphl,er It con­Slsls Of !leVeral Identical ampll lier stagesWith a cuut-m recti he' The ampli tlers areconnec ted In series and are adj usted lo r10 dB per stage A stage With an Inpu timped ance In the order 01 lero U adds thetecuner currents and passes them on to theV·ampllfler of an OSCIlloscope Figur. 10shows th e developmen t of the vlf1ually,deal c a-nneer scale

A voltage·hnear display II also poss,ble andthIs II the reason 10' lhe deSigna tionlinear/loga'l thmlc ampll l,er ThIS can beselec ted With SWitch 5 1 (Flguf. 11) to fmdthe ampli fie r st"gf> 2 to 9 that II Stili operet­mg tn Its hnear range, accordmg to themput level

The Impedance eoove-te- (LM 324) IS fOI.lowed by an active low -pass " ite' Withvariable bandwrotn , equipped With a cern.pensa ted operational ampli ',er type L 141lor stablhly reasons A meter IS also con­nec ted here for readmg 011 the amplitudevalue o f an IndiVidual spectral nne . which IIusually more accura te than when uSing anOSCi lloscope

2.5. IF·p,.tamplif ler

The croce ml ler used In the UHF-tuner hallQUIte a good IMge-slgnal handling capa ­bility. but elh,bll ll a convors.on 1055 For

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FI'II 11: G.n.r'lIon ol lh. Y.,llIn,1 ,nd Indlc, lo r circuli

thIs reason. a lew-norse preampll tler assho wn 10 Flg u,e 12 IS connec ted 10 r-oot ofThe linear/ logari thmiC IF-ampli fIer

An addi tional ' Iller can be connec ted at tneou tput Of thiS arnputra r fo r ImprovlOg serec ­ltVlty. If me nner IS bridged. resister Ad ISprovided to compensate tor the converstc nloss 01 t t us fil ler rn the passband range Inlh ,s manner II IS possible to adJusI theove ra ll gain 10 be me same In every operal ·109 mode ,

Th iS crrcuu is also able to co mpensate 'orgam uuctuanons durlOg prem-x -cperauon

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FI'II . 12, IF.p ,. , mpUfI.r 10 . 39 MHz

by allering lhe G z-vorteqe Trimmer resrs ­tors are orovrcec for tms. wh 'Ch are swnch­eo With a tenner water of SWIIch 52 All m­cuctancee are wound on 4 3 mm era coilfor me rs wl lh vroret cores

2.6. Deflect ion Module

Since most OSCilloscopes do not nave anou tpu t fo r sawtoom voltage , Ihe ceuecnonvo ltage is gene rated In the spec trum ana ­tyler Specrahsts can lhus USE' an aocruonarposSlblll ly or equahltng the luning votlagefor trequancy-hneae dIsplay on lhe x -ans

DL 8 ZX

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dulctor " I J.... ' 1_.- ~ ,- - --Ewl ~ CO 4016- (C0 4066)

R6180k

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11 ~I-

5, ~1 1fS (27~i

" 0'0'11k

PJ15k

B20~

5k6

, 10 '0'

59.

-

already cause a " aq uency Shill 01 , MHz

3. CONSTRUCTION DETAil S

All modulM should be cons truc ted Inmetet-ptete cases , and all DC and avo.c­' raq uency vcnecee should be led via teec ­l hrough capac llors In order 10 achieve lhalevery module IS RF-Ilghl All modules arel hen accommodaled In a co mmon metalcase, w hose dImenSiOns are sulllclenllylarge so that any mterecncn between themodules can be compensated lo r bychanging tee ccemcn 01 lhal module In thecase A large number 01 very strong trans­mi llers (SW. IIHF-brOadCasllng . Til ) are tobe fou nd In Ih,s Wide 'raquency range. andIt IS necessary to ensure that these are no tInt roduced InlO the System It IS alsonecessary '0 prOVide a co wer-nne ' ,Iler. butttns IS only 01 ad vantage when rne rest 01the case IS RF-t,ght

The de scription given In IIIsouacre layout 101 Ih,s C!fCU,!

The au th or used a ceuecnco moclulp alldnSClibad ,n Ill, thai was mootuoo !IO thlltlho x -oeuecnoe frequency " continuo uslyvariable (Figure 13) Th iS IS m.lde With theta noe m -potennomet e r P 1 Th iS lldlusl.lh,lI·ty 15 reql./I.ed lo r millchmg 10 the IranSClenlbehaVIour 01d,IIerenIIF-,.ltefs

The oeuecuco module also gen erat es anV·level lme. as well as a br,gh\rle ss·markc.on the X -a~15 The OSCilloscope usod musthowever possess DC·coupled X IlOd y .amplifiers due to Ihe slow proce ssespresent

•

The 'u rt her proc ess ing 01 lhe x -neuecucnvonaee. as well as the general 'o n 01 tholun,ng voueoe lor tne UHF -tuner IS g,vlm InFigure 14 II should be mentioned 'oat 'h elunmg vollago must be extremely nee 01

i l norse and hum volla9~ , Since 60 mil Wil l

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2N1613

0680

t l< X-ou tpu t-=-OL 8 ZXoil. 9"'........ •, (I'f"O .~! 27~- 'OV • __

27k -= _= .'ID3> 1) 10: 'Ok • - , . 2LV2

t l1 7 . -<=}- . ~~ ~.10: ~ • • 10 ' I" 00tx; 'lll OJ9k 1 = 10: • .. '"11 - 1k 1.1<""",7

- 0 ~. ..OQ!_27k ~ ....,.... 15k F • , l M 32l. 271.1.

o--C:) .. ~. -- . . -. 0

Sa wtoo th Inpu f 1" " 1S0p= I.....J :~':010k ~" . .. ~ _ . .....

10 k ':' 11 '4 __ c=:J- .~ 1k""1-c'J.llE'-;- " "-: 'Ok .; 11 , = t?\._.....~. :r-=- ..- 2 N370':f-<

1.'!Z. ~ =""7.. ov~ -'(IV ' 1< 50,.· 1QV

4. SENS ITIVITY, CALIBRATION

The aul hof a prolotJpe was designed 10' •ma ..,mum Input VOl tage of 30 mil lor lu ll ­sca le md,cal l()l'l (freq uency range til r lMotwo premuer ·rllOgeS I and III exhibIt anadc!,!fonai aflenual lOn of apprOximately 10ea. whIch 'It'l 'IS the dyf1am ,c range 10 10dB This lou was compensated 10' - wIlh."IImllS - by usu'Ig an I F·preamphl~1 1_251 wh OM ga,n was ...aflable F'xed allen u ­8104'·hn kl Of • bulll -,n cahbr ated a ltef'!ua lOI

can be used !of i1ltenUilltng 1'110"'" InputIe\oels SUCh allenualors .re a....,lablecommerCIally trom appro_ OM 350 ­

When !he Irequency d4N',alt on 's sw' tched0 11 ' I IS poss,ble to use l he spectrum anaIy l er 85 measunng rere'vt' r In th Is taMtne VCO can be I wepl manually USing aroteonomet.., The bUIII ·,n meter then md l·cates the rever Sin ce me spec trum analy,!"ope,ales In a dB ·lInea, manner . tne meterwoll not require a specrar cali bratIOn

The mOdulato on 0 1 'ad,o s,gnals can bemonitored usmg SUitable dem(ldulal o, sconnec ted to lhe IF-output

F,nally IIII pou<ble 10 prOVIde a Ireq uencymarker l o r lhe IreqU4lflC)' a••s wtll ch 15 lOO­sely couplud 10 the Input Fo r Instance. th.,

ca li b ra tion spec tru m genera tor cescneecby DC 6 HY wou ld tMI SUolable lor th'l

The spectrum anal ylltf could be e .tendedby anumbet' 0 1 lurther pOlSl b,IoIIM t.....,al low Ih,. syslem to be e deoOed 10 lorm aversahle and Jfle'pens,... me8surong s)"5t('fTllor radiO ama teur . ()l COU,y 'I IS nol abll"10 compete w.l h ".pens,.... prolO'lSSlOllalanalyle,s

The au thor and the publishers wou ld I! ~e tohea r your v 0ew5 on ,mprOVlng or Slmplo'ylngconstruCtion. and on any addltoons thaIcome to mind

5. REFERENCES

III E Berbero ch .OL 8Zx A Spec trumAna'yler lor Amateur Ap plocatoonsVHF COMMUNICATIONS 9.Ed,hOn 211977, pages ,l 09 ·120

(2) M Arnoldt Er/eugung yon Spek trum­d arSlellungen im UKW ·B'Ir " .chFunllschau 1977 Ed,toon 11. pag" 489

(3) Or Ing W SChmillSpe ll l rum .Analysa torenElelllron ,ll ·l ndusl ro " Ed,hon 12 /1919and 111980

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Eugen Berberich, DL 8 ZX

A Spectrum Analyzerfor VHF/UHF Amateurs

Part 2: PC-Board for the Premixer Module

In Edition 411180 01 VHF COMMUNICATIONS,th••uthor d••c rl~d • Iplctrum .n.IYZlrlorhoml conltrucllon lot th. thr.. fr.qu.ncyr.ng,. of: 1- 400 MHz, 430 - s ee MHz, .nd1230-1eOO MHz. A ,o-n1lect pr.ml..t w..r.qulr,d for th.low.st.nd hlgMlIlr.qulncyrlng'l. Th, po,ltlon of tM componlnl, InIhll modul, II rlth,r crlt lc.1 If the crOIl·tlrkb,tw"n the chlnn.1111 to b' k.ptlow. Th..uthor Informed u, In th. orlglnll Ittlcll thaihi would d', crlb, I prov'd PC-board for th.praml..r modul,. In Iddltlon to thla , tunh.tdetafla ar. to bl glvln r.gardlng a 38 MHzh.Ucal IIlll r with O-multlpll.r lor thl Intar­m.dlata fr. qul ncy of thl 'plctrum In.lyzer.

1.CIRCUIT OF THE PREMIXER

Th. circuit diagram giv. n in Figur. 7 01 thlorigInal artlcl, w.. lurthar Improved In th.d,vllopment 01 the finll Vl riion whichII InownIn Figur. 1.

Swllchlng dlodel type BA 182 (or BA 283) .rlUled lor IWitchlng thl Irequ.ncy r.ngel. Thehlgh·pall fllt.r lor Ir,quency r.nge III (1230 ­1600 MHz) comprllal printed Inductl nc.. (L 5and L 8) and thr•• c.ramlc capacltorl (C 1

23.

C 3). Th. SChottky ring mixer type SAM·5 (Mini.Circulll) requlr.. In oaelllllor power 01 7 dBm(5 mW). According to Ih. dlta Ihell, lhe InputIrequ.ncy r.ng. il 'rom 5 10 1500 MHz.According 10 thll. thl pr.mi... r will not op.r.teoptlmumly In th.l..l 100 MHz of rang. Ill . The.Il.nullor linkcomprllingr..il lora A5, A6 .ndA 7 provld... wld.ba nd, ohmic l. rmlnll ion IIth,outputo'th, ring ml...r(plnl 3 I nd4). ItII notnee....ry to procur. , ..otic r..lltanca v.luil inorder 10 achl,v. an ....ct 3.0 dB allenulllon;when ullng lh. glv.n v.lu" , a good matching IIoblalned with 3.15 ea . Fln. lly, It ahould b.m,nllontcl th.l the v.luel at both chok.. AFC 1.nd AFC 2 .re not critical.

••CONSTRUCTION

PC·bo.rd DL I ZX 004 W.I developed lor lhepr.mlx.ar. Th. dlm.nllOnl .r.35 mm .. 70 mm,Ind It II double-coaled, (I" FIg. 2). Thecomponl nt . id. of tha bo.rd II In lh. lorm 01 •conllnuou. ground lurfac., which I. onlybrokan.round thl connection f••dl 01 the compon.ntlthal.r. not grounded, With lh. aid 01. drill. Themodul. mUll be complately Icreaned bymounting il ln • conv.ntlon.1metal box.

OLe ZXco,

<>#,,'

fl; . I :The"........module h•• lho..........nng tnp.IIITwo olll'lHe .tori""" wffll .....lid 01 • wldeunclling ",I• .,. lhe 1"lrelcan be dlrectl, COft­Meled 10 It\<tlu _wtll'loul con....,.,IotI.

Thr.. ,Mdlhrough capac,1Oft ancllrvtl mlnlAtur,eoa_i-' connectorl are i~ In lhe SIde~neI• . II re(lulrltd ,11 is poNItH lor coaxial cableto ~ a.rllC lly SCl6(Mre<l to th. PC-t>oIrd and 10 bepauec:llhrough the aICl.p.lneI ollhe bel_ Ullngtubu lar nv.tl

3.A HELICAL AtTER FOR 39 MHzWITH Q·MULTIPLIER

A39 MHzIF·p,..mpl,h" wUlho\Iwn In Figur.'2ol lh. ong ,nal publicatIOn. The neIIC.' ' ,Ile' withQ..mult,plt't 'I now10 be dllCf'bed to allow thl'

amph"., 10be rMtZed

FIgu~ 3 shows • twe).SI~ NI'IClPUS flit.,ll'I*:lalrom IO-CIII«l NliCal eire..-" w!'IOM rllgha il iO be increaMd lu l'1l'1et' "'ling. Q-mult,ploerIt is eqUipped Wll h the high-power FET P 8000(p 8002). The CIrculi a.agram shoWl 1!'Ie (ran­Slstor and OII'l4tr parts OUliida of ,,,. !mil" c.rCulllor c..nty; hoMvef,lM lrnSlltor, tru.. chok..,I, rma~ . .. ........ as the bypUt capacltOrt

and 'Hislor are aclually tnl ,alled .,lIun lhe two­chlimbM bel_ OM f..clthrough C4lpacllCW, each,conn«:llthe CirculI 10 lhe ope.alng VOllege and10 the pot~hOl'neter 10. edjuSlment 01 the ().multlphel' .

•IDL8Zx

00.

10 0110 0(10l p '. JP

.­f Fig . 2:TN PC-bo.,d 01IN p..mio.,,. doutM-cNlItd.net ,.'nl1.r..d 'n. !!WI.' U".

•Qm·.m_f"oAIlI_

L- - - - _ 70 J231

VHF COMMUNIC" TJONS ~1&1

Low -c.ap QC, tan<:'

CoupI"'1l ...". rndthl'Oullh-, CJ 5, /

C2 e'

" ",,,L2 : L1,,,

FI';J , 3:T.....O·II.g. h'llcai mlfr..... Ith Q.multlpll" lor th.39 MHz IF.

The helical bandpass filter 15 deSigned torinstallation In IWO metar-ptete cases whosedimensions are 74 )< 111 )< 50 mm (dimensionsot Ihe cover). The inductances are constructedas tonows:

L. 1: 21 lurns ot silver.plated copper wire ot1.S mm dia.. wound on a 25 mm termer .sell-supporting. coil tap: 1 turn trom thecotd end,

L. 2: As L 1, bUI coil tap al4 turns from tne coldend.Inpul and outpul coupling : one lurn , each ,01 insulated wire at the cotd endol L1, or l2.

tn order to avoid any mlcrophonic -type euectsdue to shock, Ihe two coils should be suppofledby PTFE·suppoflS or strips at the center .

The mouctances are putted out to approximately3/4 ot Ihe length or the case. and broughl 10resonance by adjusting the ceramic tubulartrimmersC 1and C 2, A coupling wire is providedbetween Ihe hot (capacitive) ends ot the coils .Trimmer C 3 extends the wire to term a capac i­tive vollage divider which allows the coupling tobe varied.

A compromise must be found between lhe slope01 the passband curve and slability. Since alladjustments affect each other, a swept-fre­quency system can only be avoided if one hasconsiderable experience in this type 01 adjust ·ment, The alignment is carried oul aller attothermodules are operahng correctly . The alignmentIs made by connecting an input signal and aUgn·ing the module according to the indication on theoscilloscope .

The sOltOrs and slall 01 VHF COMMUNICATIONS would like to wish att readers a happy andprosperous New Yelr.

Weare sorry thlt you have received this edition too late. but this was caused by the unfor tunate eeeinat our printer . Mr. Gert Reichenbach , who fell sick and died whilst preparing this edition,

23.