Modifying the PRM80 Series Radios

Modifying the PRM80 series radios

Author: Michel G MitauxVersion: 6.1 (July 2002)

Original of this document can be found at: www26.brinkster.com/mitaux80/index.html and at (updated less frequently at this location, but also has info on other two way radios, and scanning info for Australia)

email:

Background

I am always impressed with Philips radios. I think that they are sensibly designed, both from a operation & design standpoint, they perform well, and are quite reliable. Philips, and more recently Simoco who took over the radio business of Philips, and even more recently with "CommGroup" (the result of Simoco dividing into two distinct 'streams' - Simoco concentrates on TETRA, and CommGroup does the normal PMR stuff now), produced many commercial two way radios for use by industry, business & emergency services. Philips also produced CB radios, though these products nowadays are not as prolific as their commercial equipment.

As far as the hobbyist is concerned, Philips produced both 27 MHz and 477 MHz CB radios. (A note for our non-Australian readers: Australia has two CB bands - the 27MHz band of 40 channels between 26.965 MHz and 27.405 MHz, with AM and SSB modes permitted, and the unique-to-Australia UHF CB band, also of 40 channels between 476.425 MHz and 477.400 MHz in FM mode, with semi-duplex repeater operation allowed on channels 1-8 as the outputs, and 31-38 as the inputs. New Zealand also has a similar UHF service on the same frequencies) Indeed, if it were not for Philips, UHF CB repeaters and even the whole UHF CB concept might never have existed today. With the exception of the ill-fated FM321, Philips have not, as far as I know, produced a radio designed for amateur use; not that this matters for much, their fine commercial two-way radios convert nicely for amateur use, and also for those looking for something a little bit different to use on the UHF CB band, too.

In recent times (well, maybe not so recent) the following Philips commercial radios have found their way into hobbyist radio enthusiasts eager hands:

FM828 - a crystal controlled, 1 to 10 channel unit, remote head or single piece that was popular during the 1970s. They are still around today, and are easy to convert into repeaters, but lack somewhat in style & features, and modern day radio designs have the edge on sensitivity and selectivity these days, but the good 'ol FM828 won't embarrass itself.

FM900 - Very popular synthesised 10, 99 or 120 channel units, remote head or single piece units, with various features & options like scanning, Selective Calling (SelCall) and CTCSS, voting and so on. Near bullet proof physical construction, very good performance and easy to operate. Popular with the amateurs on 2 metres, 70cm and with some work, the 70 MHz VHF versions can be converted to 6 metres. Also popular with the UHF CB brigade who want something that little bit special: maybe 25 watts (which is of course illegal on UHF CB) or something that will transmit 5 watts all day long without getting stressed, or maybe chosen for the excellent manners exhibited when faced with an interference laden spectrum. At first, the W1 band (470-490 MHz) radios were the units of choice for CB, but it didn't take too long to discover that the U band (450-470 MHz) or the W2 band (490-520 MHz) units could stretch their legs into the 477 MHz CB band with a bit of encouragement. Someone had also managed to 'hack' the Field Personality Programmer (FPP), the software used to program the RF frequencies / channels and other features onto EPROM for the FM900, enabling the radio to receive frequencies outside the normal designated band of the unit, or to enable 25 watts on UHF CB. The original FPP software didn't allow the radios to venture outside their normal frequency limits, or allow high power operation on UHF CB.

The PRM80

And now we come to the PRM80 units. These are more modern day units (circa 1989) which offer a plethora of features all customisable with software, remote head or single piece units, 10, 64, 100 or 200 channel units, and a trunking option was available, too. Alpha-numeric channel names were available on one model, the 8040. All this in a radio that is somewhat smaller & lighter than the FM900, modern-day styling, highly interference resistant and very sensitive to weak signals. The PRM80 series of radios has only recently been replaced by the Simoco 9000 series radios, though the PRM80 series continues to be supported.

The PRM80 family consists of:

*PRM8010 - a local mount only, 10 channel version with a single digit display (two digits for the trunked version) and only four function buttons, CTCSS and fixed SelCall system.

*PRM8020-alocalmountonly,64channelversionwith4digitdisplay,eightfunctionbuttons,CTCSSandvariableSelCallsystem,andscanning

*PRM8025-alocalmountonly,100channelversionwith4oroptional6digitdisplay,eightfunctionbuttons,CTCSSandvariableSelCallsystem,andscanningandvoting

*PRM8030-aremotemount,100channelversionwitheither4digitremoteheadoroptional6digitremotehead,eightfunctionbuttons,CTCSSandvariableSelCallsystem,DTMFandscanningandvoting

*PRM8030DualMode-sameasthePRM8030,butadditionallycanhavetwotrunkingnetworksprogrammedin(thetrunkednetworkfeatureisnotmuchusetoushobbyists,evenforreceiveonly,sincetheunitmust'register'withthenetwork)
*PRM8040-aremotemount,200channelversion,withalpha-numericdisplayremotehead,functionfullkeypadbuiltin,CTCSSandvariableSelCallwithmemorylist,DTMF,scanningandvoting. TopofthelinePMRunit,producedonlyinAustralia
*PRM8041DualMode-sameasthePRM8040,butcanhavetrunkingnetworksprogrammedinaswellasthePMRchannels.
UKmodels:
*8060Band3(175-220MHz)trunkedvisuallyidenticalto8010
*8070ditto8060butlike8020
*8061datamobilewithoutdisplayforsuchasFireServicemobilising,mainlyE-band(68-88MHz)
Dedicatedtrunkingunitsarealsoavailable,butarenotmuchusetousinthisform.
Theycannotbeusedasstandardtwo-wayradios(iePMRmode),althoughIhaveshownthatwithreplacementofthefirmwareEPROM,theycanbeusedasanormalPMRradio.Othermodsarerequired(0ohmSMDresistorjumpers)toenableSelCallsignalling. Modelsincluded8025T(curiouslylabelledas8020T),8030T,8041T,8042T,8060T,8070T,andsupposedlyamodelthatlookslikea8010. CertainlyadualmodeunitcanbetransformedintoasinglemodeunitbyreplacementoftheEPROMandalteringsomejumpers-notthatthereismuchpointindoingthis,becausethedualmodeunitscanbeprogrammedinPMRmodeanyway.
Variousoptionsarealsoavailable,suchas:
*6digitlocalorremoteheads-usedtoupgradeaPRM8030or8025froma4digithead
*DTMFmicrophone-canbeconnectedtoanyofthePRM80familytotransmit
DTMFtones,usefulforthoseradiosthatdonothavebuilt-inDTMFcapability.
*Controller(keypad)microphone-looksalmostidenticaltotheDTMFmicrophone,
butcanbeusedtoobtainextrafunctionsontheradio,anddirectlyenterSelCallnumbersetc. Thismicrophonewillonlyworkon6digitheads(ie8025or8030withtheoptional6digithead)
*Powersupplyconsoleunit(forremote'basestation'use)
*Modemcard(fortransmissionofdata,andprogrammingtheradiopersonality)
*voicesynthesisercardfortrunkingoperation
*handsfreemicrophonesetup
*covertmicrophone
*numerousoutboardoptions-MAP27datainterface,GPSAVLsystems,etcetc
*andplentyofotheroptionsIwouldn'tevenknowabout
BecausethePRM80shaveonlyjustbeensuperseded,thepricesarestillreasonablyhigh,especiallyfortheW1band(ieUHFCB)models. Youcanexpecttopayanywherefrom$300to$700forasecondhandunit,orslightlylessforotherbands. EventhetopoftherangeFM900FM91W1bandmodelsstillfetchupto$600,fora20yearoldradio!(thoughhalfthispriceismorecommonnow)
Themainreasonwhyradiossuchasthesestillcarryhighpricetagsiseasilyexplained:supplydemand. Demandforhigh-power,ultra-customisableUHFCBsishigh,andtherewasonlyafinitenumberofradiosproduced. ThissituationwasalsoapparentforAbandFM900swhichweresuitableforuseonthe2metreamateurband,althoughhasbeenlargelyovercomerecentlybylargefleetsdisposingoftheiroldFM900units,sometimesforpricesaslowas$10each. (ieVictorianCFA)
Thissituationgotmethinking:sowhycanaVHFFM900beboughtforaslittleas$10,andtheUHFunitsgoforasmuchas$600,andhowdoesthatsituationapplytomyradioofchoice:thePRM80,particularlythePRM8030? Ithoughtthatthissituationwasalittleunfair;kindalikewantingtobuyaparticularmodelcar,thenormalpriceis$5000,butifyouwantitinred,itwillcostthreetimesasmuchormore.
WhatwouldyousayifItoldyouthatyoucanbuyaPRM80inabandthatnobody(almost!)wantseg:aEband70MHzorW4band500-520MHzforasong(try$100to$150),andmodifyittoanybandyouwant? OrbuyafaultyPRM80,onethatdoesn'ttransmitorreceive,andhaveahighprobabilitythatyoucanrepairmodifyitusingthesamemagic? Ifyouareexperiencedinsolderingandhavesomeknowledgeonradiotheory,it'sprettyeasy,andintheprocessyouwillsavesomeseriousmoney. Andyouwilllearnabit,too. Bewarned,however,thisisno'snipadiode'mod-itisafullonretuneinsomecases,andyouwillneedsomeknowledgeonthegenericinnerworkingsofmodernradiocircuitsandtuneupappropriatetestequipment.
GettingtoknowthePRM80
Beforedivingintothemodificationinfo,letslearnabitaboutthedesignofthePRM80. Firstly,thePRM80canbedividedupintothreediscreteelectronicsections:thedisplayuserinterface,theRFboard(bothRXTX)andthesystemscontrolboard. TheRFboardseemstobecommontoallmodels,forexample,ifyoubuyaUbandPRM8010,8020,8025,80308040,youwillfindthattheyallsharethesameRFboard(well,notquite,butcloseenoughformostofourpurposes;theRFboardsfrommost8010sand8020scouldnothandlevotingorRSSI;thatisareceivedsignalstrengthindicator). Notonlythat,buttheinterfacebetweenthecontrolboardandtheRFboardiscommonnomatterwhatfrequencybandunityouget. ThisopensupthepossibilityofgettingaVHFunit,andreplacingtheRFboardwithaUHFone,andgettingtheradioupandoperatingonaUHFband. Oritcanbedonetheotherwayroundtogetaunitcapableofoperatingonthe2metreband. Notonlythat,butyoucanalsogetaUband(becareful,seemorebelow)oraW4bandunit,andgetittooperateonUHFCB. AndjustliketheFM900hackedsoftware,youcanalsoprogramoutofbandfrequenciesorhighpoweronUHFCBchannelsforthePRM80aswell. Letscoverthesimpleconversionsfirst,introducingvarious'tricks'andconcepts,workingourwayuptomorecomplicatedconversions. EvenifyouarenotinterestedingettingyourPRM80ontothe2metreamateurbandforexample,itissuggestedthatyoureadallsectionsanyway,becauseeachsectiondetailssomethingusefulorsomeoperationthatmayberequiredforanotherconversionwhichyoumaybeinterestedin. Let'sbegin:
TheA9bandto2metre(144MHz)amateurconversion:
IfyouarelookingtogetaPRM80for2metreamateuroperation,buyanA9(146-174MHz)bandPRM80,thenallyouneedtodoistore-programthehardwarecodetomaketheunitthinkitisaB0(132-156MHz)bandunit,andthendirectlyprogramtherequired2metrefrequencies. ThistaskiseasyonaPRM8030or8025,sincethesoftwarethatyouusetoprogramthefrequenciesandgenerallycustomisetheradioalsohastheabilitytochangethehardwarecode. Todothisforthe8030or8025,followthesesteps:
1)UsingFPP,readthepresentconfigurationfromtheradio,andsaveitasafile. Thatway,ifthingsgowrong,youcansetyourradiobacktothewayitwasandstartover.
2)Takenoteofyourhardwarecode.
3)Disconnecttheprogramminginterfacecablefromtheradio,andstartanewjob,selectingahardwarecodethatisascloseaspossibletotheoneyoualreadyhave,butthistimeintheB0band. Forexampleifyouhada952500110840,youwouldchoosea952500110841.
4)Programyourradioasdesired,thenwritetheconfigurationtothemobile. Afterasecondortwo,FPPwillaskyoutoconfirmchangeofthehardwarecode-answer'yes'.
Idon'thavespecificinstructionsforthe8010or8020,sinceIhaveneverchangedhardwarecodeswiththeseunits,butIdoknowthattherearetwoseparateprogramsforthe80108020-onetomodifythehardwarecode,andonetosetthesoftwarefeaturesfrequencies.
Ofcourse,ifyouonlywantaccesstofrequenciesabove146MHz,thenkeepingtheradioasanA9bandiseasiest. Or,youcouldevenfiddlearoundwiththeout-of-bandfrequencyprogrammingdetailedbelowtogetaccesstofrequenciesbelow146MHzeveniftheunitisstillprogrammedasanA9bandunit. Re-tuningthereceivefrontendfilters,TXandRXVCOswillbenecessaryforoptimumperformance. TuningtheVHFfrontendiscarriedoutusingthefollowingprocedure:
1)Selectthechannelforthehighestreceivefrequency,andsetupaRFsignalgeneratortothisfrequencyat50uVpd
2)AdjustR557(andR554ifneeded)for18.0VDC+0/-1VatTP403
3)UsingaCRO(ACcoupled)probepin2ofU401,andadjustthetuningcoresofFL400andFL401formaximumwaveformlevelontheCRO,reducingtheinputRFsignaliftheobservedwaveformstopsincreasing. Thewaveformisgoingtobeprettysmall,andis455kHzinfrequency.
4)SelectthechannelforthelowestreceivefrequencyandsettheRFsignalgeneratortothatfrequency
5)AdjustR554formaximumobservedwaveformlevelontheCRO
6)Selectthechannelforthehighestreceivefrequency,andsettheRFsignalgeneratortothisfrequency(again)
7)Re-adjustR557formaximumobservedwaveformlevelontheCRO. OnlyaslightadjustmentofR557shouldbeneeded.
8)Repeatsteps4to7again
9)DisconnectRFsignalgenerator,open(disable)mute,andadjustL404formaximumaudiooutput. Thenusinganoff-airsignal,preferablyonethatisalittleweak,adjustL404forminimumdistortion.
TuningtheVCOsisfairlyeasyforVHF-theprocedureisreproducedhereforyourinformation:
VHFreceiveVCO:
1)Selectthechannelforthehighestreceivefrequency
2)AdjustL407for15.0VDC+/-0.2VatTP402
3)Selectthechannelforthelowestreceivefrequency
4)ThevoltmeterreadingatTP402shouldbesomewherebetween5and13VDC
VHFtransmitVCO
1)SelectthechannelforthehighesttransmitfrequencyandactivatePTT
2)AdjustL445for15.0VDC(AorBband)or16.0VDC(Eband)both+/-0.2VatTP402
3)ReleasePTT,selectthechannelforthelowesttransmitfrequency,reactivatePTT
4)ThevoltmeterreadingatTP402shouldbesomewherebetween3and5volts
Ifinstep4forbothRXandTXthevoltagemeasuredishigherthantherangeindicated,don'tworrytoomuch,solongastheunithasstableRXTXatthehighestlowestfrequencychannels. IfounditeasiertotunetheVCO(bothTXRX)for6voltsat144MHzwhenprogrammingtuningforthetwometreband,sinceitisnotpossibletoobtainanymorethan10voltsatTP402at148MHzorso.
Tuningthereferenceoscillatoriseasy:selectamid-frequencytransmitchannel,activatethePTTandadjustL411(orthetrimcapvisibleintheTCXOmoduleforthosethathavethehigherstabilityoscillator)forthecorrectfrequency+/-500Hz. Don'tforgettore-dothisadjustmentafteryouhaverefittedtheRFshield.
TheUbandtoUHFCBconversion:
Similarly,ifyouwantaUHFCBPRM80,youcanbuyaUbandunit,reprogramthehardwarecodeasaW1bandunit,andprogramtheUHFCBfrequenciesyouneed. JustfollowtheprocedureabovefortheA9bandtoB0bandconversion. WiththeUbandpullinguptoW1band,youwillloosesomesensitivity,however,andifyouwanttolaterfooltheradiointohighpowerTX,thenyoumaysufferfromTXinstability.AnalternativetothisistosimplyprogramintheUHFCBfrequenciesusingtheoutofbandfrequencyentryproceduredetailedbelow. Thismethodwouldprobablybethesaferofthetwo,butwillnotovercomethepossiblelackofTXstabilityorlossofRXsensitivity.
Caution:SometimesaUbandunitjustsimplywon'toperateatUHFCBfrequenciesatall,duetotheVCOsimplynotwantingtobudgeaninch(kilohertz?)above470MHz. IhavefoundthattheUbandunitscanmostlybeencouragedupto474or475MHz,butnotmuchfurther. Ifthereisaneasybutreliable'bodge'jobfixforthis,thenI'dbeinterestedtohearfromyou...
ItispossibletomodifytheRXVCOresonator(andyouwillneedtodosomethingsimilartotheTXVCOresonator,too)toshiftit'scoverageupslightly,maybe2or3MHz,byverycarefullydesolderingandextracarefullyremovingthecentre'plunger'fromtheresonator,and'shortening'theloopontheplungerbyfillinginsomeoftheloopwithsolder,only1or2mmatmost,andfilingthesameamountofftheend. Thenre-inserttheshortenedplungerandsolderasyoufoundit. ThismayjustgiveyouenoughcoveragetooperateaUbandunitatUHFCB,butresultswillvaryslightlyfromradiotoradio.
Ifyouwanttoraisethefrequencyofoperationfurther,youwillneedtodesoldertheentireresonatorandshortenboththecentreplungerandtheresonatorbodyitself-andbecausethebodyismadeofceramicwithasoldersubstratecoating,thiswouldbeanenourmousamountofworkandIthinkitwouldbeeasiertobuyaRFboardinthebandyouneed.
Anotherthoughtwouldbetouseaveryfinefiletoshortentheresonatorin-situ. BecauseofthesurroundingcomponentsandproximityofthePCBatthebottom,youmightneedtodothisatanangle,butdoingsoI'msurewouldreducetheQoftheresonator. Iwonderifa'Dremel'toolwithasanding/grinding/polishingdiscorotherbitscouldgetinthereandshortentheresonatoratanicerightangle? Youcouldthenpaintsomesortofconductivepaintovertheendoftheresonatortocompletethejob. Ihaveseena'liquidsolderpaint'thatadherestoceramicthatlooksidealforthis. Thesearejustmyideas-I'mnotbraveenoughtoactuallytrythemout! Ifsomeonedoeshaveagoatthis,letmeknowtheresults...
Yetanotherthoughtcouldbetoremoveorsubstituteoneofthesmallfixedvaluesurfacemountcapacitors(notanyoftheblackvaricaps)thatsitneareachoftheresonators. Iamnotsureexactlywhichcapacitorsyouwouldneedtomodify,anditmaynotbepossibletoachieveverymuch'pull'. Obviouslyyouwillneedacircuitdiagramtodeterminewhichcapacitorswouldbebesttoachievethis. Again,thisisjustmythoughts,andIhavenotattemptedthisprocedure. Again,ifsomeonedoeshaveagoatthis,letmeknow!
TheW4bandtoUHFCBconversion:
Myfavourite! Re-programmingaW4bandunitintothinkingitisaW1bandfollowstheverysameprocedureoutlinedabove. However,thistime,therearethingsyoucandotoimprovetheperformanceoftheW4RFboardatthelowerfrequencies. Justre-programmingtheunitfromaW4toW1banddoesnotworkforfrequenciesbelowabout485MHz(oratleastthat'swhatIfound),soyouwillneedtodothis:buyseven'R4001' 2to7pftrimmercapacitorsfromAltronics( Actually,buyabout10lotsofR4001-sometimesthelegsofthetrimcapswheretheypassthroughtheceramicsubstrateeitherbreak,orhaveunreliablejoinstothecapacitorplatesandthisisnoteasytofixorrepair(itcanbedone,butyouneedtobeprettygoodonthesolderingiron-fast,accurate,andaslittleextrasolderaspossible,butthatliquidsolderpaintIspokeofjustabovewouldprobablydojustaswell)
WhenpurchasingyourR4001trimcaps,dotrytomakesurethattheyareindeedR4001types(2-7pF). Thesehaveasplashofredpaintonthetop. Look-a-likesandothercolourpaintmarkingsshouldberejected,sincetheyareprobablynot2-7pF. Likewise,otherversionsof2-7pForsimilarvalue,suchastheDickSmithR2940orR2935(theremightbeothersfromJaycaretc)shouldallbeleftalone. Theyarenotphysicallysmallenoughtodothejob. TheAltronicR4001istheonlyoneofit'stypethatissuitableandisreadilyavailable.
NowthatyouhaveyourR4001's,solderingacrosstheresonatormeanstosolderonelegofthetrimcaptothecentreconnectionoftheresonator,preferablynearwherethecentreoftheresonatorissolderedtothePCBandtheotherlegofthetrimcapgoestothetopoutsideoftheresonator,whichisearthed. BecarefulwhenorientingthetrimcaptokeepthetrimcapprofilelowsothatthemetalRFshielddoesn'tshortoutonthetrimcapwheninplace. Alsobecarefulthatthetrimcapdoesn'tshortoutontheedgeoftheresonatororothercomponentsofthePCB. Beneatwithyoursoldering,andusetheminimumamounttoformagoodjoint-toomuchsolder(orheat!)canadverselyaffecttheresonatorsperformance. Averyfinetipsolderingironisamust-ifyouhavetogooutandbuyatipspeciallyforthisjob,doit! Andhandlethetrimcapsverycarefully-theyareveryfragile.
Tuningthetrimcapsisthenextstep. Thisprocessismademucheasierifyouhaveaccesstoasignalgeneratorandspectrumanalyser,butwithcopiousamountsofpersistence,youshouldbeabletotunethemwithoutthoseluxuries. Youwillneedanon-metallictuningwand/adjusterforthistask,Irecommendaceramicbladescrewdriver. Getoneifyoudon'thaveone,oryouwillprematurelylooseallyourhair! YouwillalsoneedtofindsomeshortscrewswithamatchingthreadtotemporarilybutsecurelyholddowntheRFboardtothechassis. Youwillgetvariableresultsotherwiseduringthetuningprocess. Becarefulnottoovertightenthescrews-theymaystriporshearoffcausingproblemslater. Justtightenthemfirmly.
StartwiththeRXVCOresonator(theonebyitselfclosestthecentreoftheRFboardnearthefrontendresonators)-startbysettingtheradiotothehighestreceivefrequencychannel,andtunetheRXVCOtrimcapsothatastrongLocalOscillator(L.O.)isvisibleatthecorrectfrequencyonthespectrumanalyser,orisaudibleonascannerreceiveratthecorrectL.O.frequency(whichwillbeyourreceivefrequencyminus21.4MHzexactly). Repeatthisprocedureforyourlowestreceivefrequency. CheckthatthehighestreceivefrequencyLOisstillbeinggeneratedforthissetting. Ifnot,gobackandforthbetweenthehighestlowestreceivefrequencychannels,verycarefullyadjustingtheRXVCOtrimcap(andR554ifabsolutelynecessary)forcorrecton-frequencygenerationoftheL.O. Ifyouselectyourfrequenciestoofarapart,theVCOmaynotbeabletocope! Havingsaidthat,myconversionshaveineachcasebeenabletospan460MHzto490MHzRXquitehappily-notbadforaboardoriginallydesignedfor494-520MHz. Ifyouareverycarefulwithyourtuningandhavemadegood,neatsolderjoinswithyourtrimcaps,yourVCOforRXcanspan38ormaybe40MHz. Again,useanon-metallicscrewdrivertoadjustR554R557.
Thesecondseriesofadjustmentsistotunethetrimcapsthatyouhaveplacedonthefivefront-endreceiveresonatorfilters. Normally,onUHFatleast,theresonatorfiltersarebroadenoughbythemselves,alongwithvaractorfrequency-trackingtocovertheoriginalbandintended. Hereweareaddingsomecapacitanceacrosstheresonatorstolowertheiroverallfrequencyofoperation. Becauseeachfilterisnowindividuallytunable,youwillbeabletomakethefrontendalittlemoresensitive,attheexpenseofbeingslightlylessbroadband. Notthatthisisamarkedeffect-aftertuningforacentreRXfrequencyof473MHz,Ifoundthattherewasonlyabout1dBperformancelossat465480MHz(yourmileagemayvary,ofcourse). Theprocedurefortuningthefrontendtrimcapsissimilartotheonelistedabove:choosethefrequencyatwhichiseitherinthemiddleofyourdesiredcoverage,orthefrequencyatwhichyouwantabsolutemaximumsensitivity,thenputastablebutweaksignalintothereceiver(don'tforgettodothisonanon-CTCSSchannel,anddisablethemute)sothatitisjustaudible. Thentuneeachtrimcapstartingwiththeonenearesttheantennaconnectorandmovingtothefrontoftheunit,ineachcasetuningforminimumnoise. Ifthesignalbecomeslargelynoise-free,thendecreasetheinputsignalagainsoamoderateamountofnoiseisapparent. Alwaystuneforminimumnoiseusingtheweakestinputsignalpossible. AnothermorescientificwayistoobservethewaveformatU401pin2,whichisproportionaltothereceivedsignalstrength.
Oncethishasbeendone,tunethetinypairofvariableresistorswhichsetthetrackinggainVCOoffset,followingtheprocedureasdetailedintheservicemanual:
1)Selectthechannelforthelowestreceivefrequency
2)SetaRFsignalgeneratortothisfrequency,at50uVpd(ormoreifneededtogetanaudiblesignal),andconnecttotheantennaconnector.
3)UsingaCRO(ACcoupled,10uSperdiv,andthewaveformwillbeprettysmall;50to100mVorso,at455kHz),probeacrosspin2ofU401,andadjustR554formaximumobservedwaveformlevel
4)Selectthechannelforthehighestreceivefrequency,andresetyourRFsignalgeneratortothisfrequency
5)AdjustR557formaximumobservedwaveformlevelontheCRO
6)Repeatsteps1-4again
7)DisconnectRFsignalgenerator,open(disable)mute,andadjustL404formaximumaudiooutput. Thenusinganoff-airsignal,preferablyonethatisalittleweak,adjustL404forminimumdistortion.
Inrarecases,youmayhavetogobackandforthbetweentuningtheRXVCOtrimcapandtheaboveprocedureforR554R557togetarelativelystableVCOoperationoverallyourchosenfrequencies. Asafinalcheck,listentotheL.O.onascannerreceiver-ifitsoundsnoisy(kindoflikearushing,windynoise),continuetuning. AspectrumanalyserhelpsgreatlywithsettinguptheRXVCO,butwithlotsoftimepatience,youcangetbywithjustascannerreceiver. Alsonotethatifyouaretryingtogetyourreceivertocovermorethan20MHz,thetrackinggainadjustmentsmaynotworkquiteasexpected,givinggoodsensitivityattheedgesoftheband,butpoorsensitivityinthemiddle. Ifthishappens,youwilljusthavetofiddletoarriveatasuitablecompromise.
Ifyouarereallysearchingformaximumsensitivityononeparticularfrequency,gothroughtuningthetrimcapsonemoretimeatthatfrequency. Otherwise,youhavenowadjustedtheradioforverygoodsensitivityacrossthebandwidth. Normally,foraW4bandboardmodifiedassuchwillproduceaminimumdetectablesignalofslightlylessthan0.10uV(ieonereallyhotreceiver),andminimummutethresholdof0.12to0.15uV.
(Hint:youcanusea'lowtech'scannerasasignalgenerator-allyouneedtodoistotunethescannertoyourdesiredfrequency+thescanner'sfirstI.F. So,ifyouwantedtogenerateatestsignalat470.000MHz,andyourscannerusesa10.7MHzI.F.,thentunethescannerto480.700MHz,andyoushouldthenhaveaweaksignalbeinggeneratedat470.000MHzcourtesyofthescannersownlocaloscillator. Ifnosignalisheard,alsotry10.7MHzbelowthedesiredfrequency:intheaboveexampletryprogramming459.300MHzonthescanner. Most'lowtech'scannersuseeither10.7,10.8,10.85or21.4MHzI.Fs. Locatethescannerasuitabledistanceawayfromyourradioundertesttoachieveasuitablyweaksignal. Thismethodisnotwithoutit'sdrawbackshowever;anyhand,armorbodymovementcanalterthereceivedstrengthonyourradio,ascanotherpeoplewalkingnearby,etcetcbutwithsomepractice,youshouldbeabletotunetheradioquitewell)
ThelastadjustmenttobemadeisfortheTXVCOfilter. AllyouneeddoistunetothehighestlowestTXfrequencychannels,andtunethetrimcapontheTXVCOfilterresonator(theresonatorallonitsown,ontheoppositesideoftheRFboardtotheRXsection)formaximumTXstability. Ifyoufindthatatfirstthisdoesn'tappeartobepossible,theTXVCOwillneedreallyfineadjustmenttoachievestableTXacrossyourchosenfrequencies,sopersistwithit. KeepinmindthattheTXVCObufferstagethatyouaretuningneedstobeshieldednormally. Becauseofthis,itiscriticalthatyouhavethescrewsinplaceholdingdownthePCBtothechassisinthevicinityoftheTXVCOresonatorfilter. Sometimesthisisnotenough,andyouwillneedtouseyourfingertopushdownonthePCBedgeneartheTXVCOresonatorfiltertoensuregoodearthingcontactwiththechassisduringtuning. Ifyoudoexperienceaproblem,itwillmanifestitselfaseithernoTXatall,orafastpulsingTX,especiallyonkey-up. Ihavefounditeasiertodoanyinitialtuningonlowpower,thendofinaladjustmentsonhighpower. Ofcourse,duringthisstage,alwaystransmitintoagooddummyload. YoushouldbeabletogetyourunittoTXacrossaspanofabout35MHzifrequired. Don'tforgetto'stresstest'yourtransmitter-keythetransmitterupforabout1minuteatatime,thenletitrestforanotherminute,andrepeatthisprocessuntiltheradioisreasonablywarm(nothot!)-ifyoufindthatyourupperorlowerchannelsarenottransmittingorreceivingafterthis,itprobablymeansyourtuningoftherespectiveVCOwasn'tquitecentredinyourchosenbandwidth. VCOsdothingslikethiswhentheygetwarm,soit'sbesttocheckandadjustaccordinglynowwhileyouhavetheradioapart,ratherthanfindoutduringalengthyconversationthatyouhadn'tcentredtheVCOtuning.
Becarefulwiththetuningofthetrimcaps-theyareveryfragile,andbecausethetrimcapshaveno'stops'intheadjustment,thatistheiradjustmentgoesaroundandaroundforever,youwillfindtwotuning'peaks'andeitherpeakshouldtheoreticallywork,butpractically,becausethetrimcapisusuallyveryclose,ifnothardupagainstthemetalshield,one'peak'mayworkoutbetterthantheother. ItreaffirmsmythoughtsthatyoudoneedtohaveabitofRFknowledgewhentuningthesecritters,whichismadesomucheasierwith'real'testequipmentlikeasig-genandCROetc.
Obviously,itwillbeeasiertotuneupamodifiedPRM80ifyourestrictit'sfrequenciestoanarrowrangeieUHFCBonly(andyouwillgetveryslightlyimprovedsensitivity,too). ThetuningbecomesslightlymoredifficultifyouwantPolice468MHzRXonlyandUHFCB,andbecomesachallengeifyouwanttoadd490MHzorlow460MHzfrequenciesintothemix,too. Normally,youwillbeabletogetabout40MHzbandwidthforreceive,and35MHzbandwidthfortransmit,butthiswilltakesomeveryfineadjustingandfiddlingtoachievethisresult. WhenusedintheRFboard's'native'band(ieaUbandboard,unmodifiedandprogrammedasaUband,Imanagedtoget425to475MHzRX,435to475MHzTX)youcanexpectnearly50MHzreceivecoverage,and40MHztransmit,usingsoftware'outofband'modsonly. Thesefigures,ofcourse,relatetoUHFversions.
OneinterestingvariantisthegenuineUWbandunit. Thesecancoverfrom443to520MHzforbothTXRXwithonlyappropriatesoftwareprogramming. Thesensitivityisonlyabout1dBbehindtheotherUHFversions,butmaintainsthissensitivitylevelprettymuchacrosstheband,droopingonlyanother3dBtowardsthebandedges. ThegenuineUWbandunitsappeartoachievetheirphenomenalbandwidthcapabilitiesbyusingnotone,buttwovaricapdiodesacrosseachVCOresonator,andthisisprobablycoupledwithappropriatesoftwarecontrolofthe'VCOpulling'voltagefedtothosevaricaps. Thereareotherchangesaswell,tohelptheVCOcoverthewiderbandwidth,butthemainchangesseemtobetheextravaricapdiodes.ProgrammingagenuineUWbandunitasaW4isprettymuchawasteoftime:TXcoverageislimitedto,strangelyenough,a10MHzareaaround510MHz,butRXisabitbetterat494to530MHz. ProgrammingagenuineUWbandunitasaUbandunitproducessomeinterestingresults:TXandRXfrom435to483MHz,meaningthatthisistheonlyPRM80variant(withappropriatesoftwaremodifications)thatcancoverboththeamateur70cmband,ifonlypartly,andUHFCB,obviouslywithreducedsensitivityatthesebandextremes,about6dBbehindthenormalfigures. ProgrammingagenuineUWbandunitasaTUbandproduces430to480MHz-similarresultstotheUbandonlyasabove. 20orsoMHzcoverageismorenormalforVHFversions.
ThisW4toW1orUWbandconversioncanalsobefollowedinprinciple(ieaddingtrimcapstotheresonators)tolowerthefrequencycoverageofanyoftheUHFunits.
Thetrimcapscanbereplacedusingfixedvaluediscceramiccapacitorsorevensurfacemountcapacitors,seenotesbelowaboutusingthesemodsinaPRM80destinedformobileuse.
ThesinglebandintoUWdualbandconversion:
Well,heresaninterestingone. JustchangingthehardwarecodealonefromasinglebandRFboardtoadualbandRFboard(ieW1intoaUW)sometimesdoesn'twork. Thedividerratioschange,andtheVCOsimplydoesnotalwayslockproperly. However,IhavepersonallychangedmanyaW4bandonlydualmode,12.5kHz radiointoaUWbandunitthatdoesquitehappilyspanfromatleast460to490MHz.TheW4RFboardwasmoddedinmuchthesamewayasdescribedabove:capacitorsaddedtotheresonatorsandcarefuladjustmentoftheVCOandtrackinggainadjustments,andprogrammedasaUWband,dualmode,25kHzunit. Notethechangefrom12.5kHzto25kHz.
YetanotherW4unit,asinglemodetypethistime,didnotmodifywelltoUWconfiguration-ithadtobechangedtoaW1bandonlyunitbecausetheVCOrefusedtolockwhileinUWconfiguration. Idonotknowwhythishappened,itmighthavesomethingtodowiththewaythedualmodefirmwarehandlesthecontrolvoltagefortheVCOs? StillanotherW4bandsinglemodeunitcouldnotbeprogrammedasaUWbandatall(theFPPsoftwarerejectedthehardwarecodechangeasbeingnotcompatible)butcouldbereprogrammedasaW1only. Youwilljusthavetotryitandsee.
IhavenottriedthismodificationusingaW1orUbandonlyRFboardtoturnitintoa'wideband'UWunit,butasimilareffectcanbeachievedbyprogrammingoutofbandfrequenciesintotheunitusingamethoddescribedbelow,withquiteacceptableresultsasdetailedabove(seethecommentsaboutusingaRFboardinit's'native'bandwithout-of-bandsoftwaremodsonly).
TheVHFtoUHF(orvice-versa)conversion:
So,youhaveboughtyourselfanEband(68-88MHz)radioreasonablycheaplyandwanttoturnitintoaUHFCB. Changethehardwarecode,andprogramUHFCBchannelsintothethingwillworkOK,won'tit? YoucertainlywillbeabletofooltheVHFradiointothinkingitisnowaUHFradio,butbelieveme,itjustwontwork! Youcan'tturnafrontwheeldrivecarintoarearwheeldrivecarbyturningtheseatsaroundtofacetheoppositedirectionanymorethanyoucanchangeaVHFradiointoaUHFradiojustbychangingthehardwarecodealone! WhatyouwillneedtodoistoremovetheVHFRFboardandreplaceitwithaUHFRFboard. OryoureplacetheRFboardwithanybandRFboardasyoudesire. WheredoyougetRFboardsinthebandthatyoudesire? Youcantryanynumberofplaces-alocalamateurradiooperator,alocalradioservicetechnician,evenanotherradioenthusiastthatmayhaveaspareRFboardinthebandyouwantasaresultofreadingthisinformation! UnfortunatelyRockbyElectronicshavenowsoldoutoftheirW4bandRFboardsasof13/3/2001. AnothersourcemightbeKeycom,whereW4bandboardscost$50,andgenuineW1boardsusedtocost$120(theyareallsoldoutofW1andA/Bbandboardsnow)whichdoesn'tincludepostage. (there'sthesupply-and-demandtheoryatworkagain). BepatientforareplyfromKeycom-heonlycheckshismailonThursdaynights,soI'mtold.
EvenIhaverunoutofRFboards,andIdon'tknowwhereyoucangetanymore,otherthanKeycom(seewebsitementionedtowardstheendofthisdocument)
Ifyoufindthatallthistuningisabitbeyondyou,Icanhelpoutthere. Ifyouarethetrustingtype,youcansendyourunittomeandIwilltune/modify/settheradioupandreturnittoyou. ormoreinformation.
TheseinstructionsareapplicableforanyRFboardchangeovers,beitfromVHFtoUHF,orVHFEbandtoVHFBorAband,oranyothercombinationthereof.
1) Poweruptheradio,connectyourinterfacecable,andreadthepresentconfiguration
2)Savetheconfiguration,soifthingsgowrong,youcanreverttotheoriginal,andmost
important,switchoffthepower,andremovethepowerplug.
3)UsingatorxT8driver,undoanyretainingscrewsontheRFshieldcoverandremove(ifpresent)
4)UnclipthecontrolboardtoRFboardribboncable,bypullingupontheedgesoftheretainingcollaroftheplasticconnector. Thisshouldallowtheribboncabletocomefreefromtheconnectorveryeasily.
5)DesoldertheantennaconnectionandthepowerfeedthroughfromtheRFboard.
6)Usingatorxdriver,unscrewthescrewsholdingtheRFboardtothechassis. AlsoundothescrewsholdingtheRFpowerdevice(s)tothechassis,andanyothertransistorsordevicesthatmaybehelddownbyscrews.
7)GentlyremovetheRFboard,andputitasideinasafeplace. Whoknows,anotherradioenthusiastmightwanttobuythatRFboardfromyou! Trytofindananti-staticbagtostoreitin...
8)Getyournewboard,andlayitinplaceontoyourchassis,andlookatthescrewholes;seeifthereareany'new'screwholesthatdonothaveathread. IfchangingfromaVHFboardtoaUHFboard,youwillfindthattheVHFchassishastheholespre-drilledbutmaynotbepre-tappedfortheUHFdriverpre-drivertransistorsorthepowercontroltransistor. Ifyoufindthatyoudoneedtotapnewthreads,youwillneedtoremovethecontrolPCBfromtheothersideofthechassis,sothatanyswarfproducedbycuttinganewthreaddoesn'tfallthroughtheholeandendupunderthecontrolPCBandcauseashortcircuit!
9)Onceyouhavecutanynewthreads(ifapplicable)wipecleananyheatsinkcompoundgoopoffthechassisandtheRFdevicesonyournewboard. Abitofmethohelpshere. Youmayaswellgivetherestofthechassisaquickwipeover,too,justtomakesurenometalchipsorswarfetcremains. ApplyathinbutevencoatingofnewheatsinkcompoundgooptotheRFpowerdevicesandtheirmatingareasonthechassis.
10)GentlypositionyournewRFboardintoplace,andreplaceanyscrewsfortheRFpowerdevices,UHFpowercontroltransistor(lookslikeablackplasticencapsulatedTO220device)ifapplicable,andthetwoscrewsneartheRXresonatorfilters(theseareindicatedbyasmallarrowonthePCB)andgentlytighten. Thentightenfurther,butnottootight(thescrewsbreakorthreadsstripquiteeasy). MakesurethatthemetalclipthatactsasaPCBspacerandheatsinkforthesmallpre-drivertransistorontheundersideoftheRFboardisinplace-itiseasyenoughtolose. Ifyoudoloseit,donotuseascrewinthathole-youwillendupbendingthePCB!
11)Soldertheantennaconnectorthepowerfeedthrough,re-inserttheribboncableandlockinplacetheretainingcollar
12)NowreprogramthehardwarecodetosuityournewRFboard(ortosuitmodificationstotheRFboard);youwillhavetotemporarilyreconnectpowertodothis.
13)PerformanymodificationsasyoudesiretotheRFboard,andtune(don'tforgetthoseextrascrewstotemporarilyholdtheboarddownasyoutuneit)
14)Onceagainremovethepowertotheradio,replacetheRFshield,andtightenthescrewsforthisfirmly,butnottootight. NoRFshield? Bettergetone-theydomakeadifference,especiallyifyouareaskingyourradiotospanareasonablebandwidthorareusingtheunitinamobileorRFhostileenvironment,andunstableTXcanresult. AlsonotethatiftheshieldcamefromaVHFunit,notalladjustmentholeswillbepresentforUHFadjustmentsandviceversa. BesttomakeasmanyadjustmentstuningbeforetheRFshieldisreplacedforgood. Onepointtonoteistoalwaysadjustthefrequencyfinetuneaftertheshieldhasbeenreplaced.
ThismethodofswappingRFboardsandmoddingW4boardstocoverW1frequenciesworks,andworksverywell. Hereareafewunabridged,verbatimquotesfromsomehappymodifiedPRM8030users: "JustthoughtI'ddropalinetosaythattheradiohasbeenworkingbeautifullysinceyoumoddedit. AnA9fittedwithaW4boardthatdoesW1frequenciesaswellasanoriginalW18030. IborrowedaW1offafriendforafewdaysandchallengedafewfriendsonradiototellmeonairwhichonewaswhich-theycouldn'tpickonefromtheother!! Iwastellinganamateurfriendofmineaboutitandheputitonhistestbenchandtoldmethatallyourquotedfiguresre:Txpower,sensitivity,etcwerespoton."
andanother:"Justgotbackfromholidays,sothisismyfirstchancetothankyouforaterrificjobyouhavedoneontheradiosIamveryverypleasedtheyworkreallywellTERRIFIC."
andanother:"Workslikeacharm!Thanksagain!"
andanother:"Andlastbutnotleasttheperformanceonnarrowband(12.5)isamasing.Thescarypartishowgoodtherxisona25ksignal,loudandclear"
Severalpeopleoverthelastsixmonthsorsohavebeenmakingcommentstotheeffectthatthesemodificationsare'butchery','performpoorly','havereducedpoweroutput','poorsensitivity','poorreliability'etcetcandthat'genuineW1saretheONLYwaytogo','itdoesn'twork'orwordstothateffect.
Icanonlypresumethatthesepeoplearebasingtheirjudgementonpoorlymodifiedortunedradios,orwanttogeneratesomeprestiegeinowningagenuineW1bandunit. Ihavemodifiedsome150W4radiostoworkonW1band,andnotoncehasanyonecomplainedoftheaboveproblems,andasyoucantellfromtheabovequotesfromhappyowners,theycertainlythinkhighlyoftheirmodifiedunits. Ipersonallytestthepoweroutput,spectralpurityandsensitivityofeachandeveryunitImodifyandhaveyettoseeaUHFW4toW1conversionachieveworsethan -12dBuV(about0.25uV)for20dBquieting,orlessthan25wattsRFpoweroutput(andyes,thisismeasuredwithcurrentin-calibrationequipment). Indeed,mymodifiedW4unitsareslightlymoresensitivethanmygenuineUWbandunit! Ithinkthatputstoresttheargumentthattheyarepoorperformers/poorinthesensitivitydepartment.
Mownmodified8030unitshavebeenwithmeforthreeyearsnow,andareindailyuse,andhavenotsufferedanyproblemsmentionedabove,sothatshouldanswerthereliabilityissue.
IdoagreethatgenuineUWradiosdocoverlargebandwidthsmuchbetterthanW4strickedintobeingUWs,butthisshouldn'tbeaconcerntomostpeoplewhoonlywanttocoverUHFCBandPoliceUHFRXonly. ThemodifiedW4sdothisfunctionexceedinglywell.
Beassuredthatthereareatleast150ofmymodifiedPRM8030sinAustraliathatarelivingproofthattheW4toW1modificationworks,andworksverywellindeed.
Icameacrossone'W4toW1'conversionthathadbeenpoorlydone;therehadbeenway,WAYtoomuchsolderused,andthesolderingironusedwasobviouslytoobigasithadburntsurroundingcomponents. Thecapacitorsusedwerenotinespeciallygoodcondition,andoverallthemodificationhadbeenpoorlyexecuted. Notsuprisingly,theradiodidnotworkverywellatall. Infact,theexcesssolderhadflowedinsidetheresonatorsandhadruinedthem. Likeanything,ifthejobiswelldone,itwillgivegoodresults. Poorworkequatestopoorresults. ThepointIamgettingathereisthattheinformationIhaveprovidedhereisgood,butIdon'thavecontroloverthequalityoftheworkthatothersdowhenusingthisinformation,sodon'tgoblamingmeifthingsgopearshaped. Ifyouhaveanydoubtsastothequalityofyoursoldering,oryourabilitytounderstandandproperlyusethisinformation,thenstop,andgetsomeoneelsetohelpyou,lestyouruinyourradio.
Usinga8010or8020RFboardina8030or8040.
TheonlyapparentdifferencebetweentheRFboardsfromthe80108020tothatusedinthe80308040isthelackofaRSSIline. Thismeansthatyourreceivedsignalstrengthindicatorwillread99whenreceivingasignaland00whenmuted,andvotingwillnotworkproperly. Thereisnofixtothisproblem,butifyoucandowithouttheRSSIandvoting,thenitwillbefine.
Programmingout-of-bandfrequenciesintoyourPRM8025/8030.
Youmayhavenoticedthatyoucan'tprogramfrequenciesoutsideofthedesignatedbandoftheradio. Forexample,ifyouhaveaW1bandonlyradio,andprogramitforUHFCB,theFPPsoftwaredoesn'tallowyoutoprogramin468MHzfrequenciesforpoliceRXonly. Thereisawayaroundit,anditusesabuginthestandardFPPsoftware. Here'showtodoit,withtwospecificexamplesofadding468MHzfrequenciesintoaW1(ormoddedW4programmedasaW1)bandunit:
1)Createyourprofilewithallthefeaturesetcthatyouwant,lessanyoutofbandfrequencies,andprogramthatintoyourradio,andtestthoroughly.
2)Onceyouarehappywithyourconfiguration,lesstheoutofbandfrequencies,re-readtheconfigurationintothePCandsavetheconfiguration. Takenoteofyourpresenthardwarecodeandwriteitdown.
3)Disconnecttheprogramminginterfacefromtheradio
4)Havetheconfigurationopen,andeditthehardwarecode(asdetailedabove)tobeaVHFA9bandunit,ofsimilarhardwareconfigurationtowhatyourunitreallyisnow.
5)Gobacktoeditingfrequencies. YouwillnoticethatyourfrequencieshavechangedintoVHFfrequencies. Thatisfine-ifyoulookcloser,youwillseethattheVHFfrequenciesactuallyrelatetoyouroriginalUHFfrequencies(thedividerratioisthesame)eg476.425MHzinW1bandbecomes155.71250MHzinA9band.
6)Nowthetrickybit:extrapolatetheoutofbandUHFfrequenciestoVHFfrequencies. HintforW1bandunits:467.850MHzbecomes151.4250MHz, 467.875MHzbecomes151.43750MHzandsoonuntil469.425MHzbecomes152.21250MHz. Thedocument
calledUtoV.docwillhelpyouwiththis.
7)Onceyouhavefinishedenteringallyour'VHF'frequencies,press'ESC'then'F2'togetbacktothemenutochangeyourhardwarecode. Changethehardwarecodebacktoyouroriginalone,andthenviewthefrequencytable. Youshouldverifythateverythingisasyouwantitbeforesavingthefile,andwritingittotheradio. Ifyoudoneedtomakechangesorcorrectamistake,youwillneedtochangethehardwarecodebacktoA9band,andeditinthatconfiguration.
8)Don'tforgetthatifyouenteroutofbandfrequencies,youmayneedtoretune(andmodifyinthecaseofUHFversions)theRXVCOtocoverthesefrequencies. Ofcourse,ifyouenterwildlyoutofbandfrequencies,theVCOwillprobablynotcopeatall!
Basedonthismethod,youcouldprogram(note:notoperate)thefollowingranges:
W1bandnormally470-500MHz,canbecome457.000MHzto513.000MHz
Ubandnormally440-470MHz,canbecome427.000MHzto483.000MHz
W2bandnormally494-520MHzcanbecome482.000MHzto538.000MHz
UWbandnormally450-520MHzcanbecome443.000MHzto520.000MHz
Tbandnormally400-440MHzcanbecome392.000MHzto448.000MHz
Ebandnormally68-88MHzcanbecome64.000MHzto92.000MHz
Bbandnormally132-156MHzcanbecome130.000MHzto158.000MHz
A9bandnormally146-174MHzcanbecome141.500MHzto180.000MHz
(toexpandtheA9bandunit,changetoTUbandtogetdownto141.500MHz,andchangetoUWbandtogetupto180MHz)
However,takenoteofthepracticaloperatingbandwidthsasnotedearlier. ThisprocedureismostusefulontheVHFand'modded'W4versions,sinceyoucan,withinreason,shifttheVCOcoveragetosuityourrequirements.
Programmingoutofbandfrequenciesonthe8020and8010issuprisinglysimple-thesoftwarejusttakesthefrequenciesasyoutype! ThesoftwarealsoallowshighpoweronUHFCBwithoutanyproblems,either.
Reallyoutofbandfrequencyentries-andwhatabout6metres?
YoucanuseahexeditorprogramtodirectlyeditthePLLdivider'words'inthedatathatgetswrittentotheEEPROM. Beginbyloadinginthefilewiththe.eprextension,andstarteditingthisfile. Lookforthedatastartingat$1C0. ThefirstpairofbytesistheRXfrequency,thenextpairforTXfrequency,andthenextthreebytesrelatetooptionsforthatchannelsuchasselcall,CTCSS,etcetc. Thenthereisabyteof$FFandthenthenextchannelfollows. Thispatterncontinuestotheendofthefile-youwillnotethatthereisenoughroomfor200channelentries-whichincludesthe100'hidden'votingchannelsthatareavailable. Onceyoufinisheditingthe'words',savethefile,andthenreloadthefileintoFPP. FPPwillcomplainthatthefileiscorrupt-justpressescapetocontinueandyouwillbeabletoseetheeffectofyourchangesinthechanneltable.
Now,whataboutprogrammingfor6metres? Well,Ihavebadnews. Theabovetrickwillonlygetyoudownto58.000MHz. I'msurethatthePLLdividerwouldphysicallybeabletogolowerthanthis,andwithabitofwork,theVCOscouldbeencouragedtogoto50oddMHz,butwhatIsuspectishappeningisthattheprograminthefirmwareisaddingafixedvaluetothe'words'writtentotheEEPROMtocomeupwiththefinaldivisionvaluethatisloadedontothebusandintothePLLIC. Maybesomekindsoulouttherewouldcaretolookdeeperintothesituation,andmaybere-writethefirmwaresothattheappropriatevaluescanbeloadedintothePLL,sothatthePRM80canfinallygetdownto52MHz.
Typicalperformancespecifications:
Youcantypicallyexpectupto35wattsoutofyourPRM80,butsettingthepowerthishighisasurewaytoreducethelongevityofyourPAstage-itwouldbebesttosetthepowerto25wattsandleaveit. Thepowershouldbesmoothlyadjustabledownto½awatt,orevenlessifyoudon'tmindnothavingtheTXindicatorlightup.
Asforsensitivity,mymoddedW4s(narrowbandor12.5kHzversions)intoW1sorUWsturninsensitivityfigureslikethis:
for10dBSINAD:0.12uVor-125.4dBm
for12dBSINAD:0.13uVor-124.7dBm
for20dBQuieting:0.19uVor-121.5dBm
Thesefiguresweremeasuredwithcurrentin-calibrationtestequipment,sothefigures,whilenotlab-accurate,shouldbeveryclose. Asyoucansee,thesensitivityisextremelygood,beingevenslightlybetterthantheverylatestGMEElectrophoneTX4400andthemuchvauntedSawtron999(akaKyodoKG107/EricssonC65/KeyK???),apairofradiosthathaveareputationofhavingveryhotreceivers. Notbadforamodified,15yearolddesign.
IfyouareluckyenoughtohaveagenuineW1(narrowband) unit,theywouldturninsensitivityfiguresapproximately1to2dBbetterthantheabove.
Allthe'normal'(25kHzbandwidth)unitswillshowfiguresapprox.2dBworsethanthefiguresgivenabove.
ForthoseofyouupgradingfromFM900s,thesensitivityisapproximately5dBbetterthanawelltunedFM900.
Theadjacentchannelrejectionisverygood,thisimpressionhavingbeengainedbymyselffromavarietyofreal-worldoperatingconditionsandbymeasurement;itwasfoundtorequriea750uVsignaltostarttocausebreakthroughonnearbyfrequencies. (TheKyodoKG107cameoutslightlybetterat1580uV). Receiverblockingisalsopracticallynil.
Youcanexpectabout20MHzflatresponseRXbandwidthoutofthePRM80UHFversions,andabout15MHzfortheVHFversions. (Ha!TheSawtron/Kyodoonlymanagesabout5MHzflatresponse!)
Performancesummary:
ThisisalistofthePRM80RFboardsforUHFCBgiveninorderofreceiveperformanceasitrelatestosensitivity:
1)GenuineW1,12.5kHzbandwidth(theoreticalonly,I'veneverseenaW1narrowbandRFboard,buttheyareknowntoexist)
2)W2,12.5kHzbandwidthmodifiedwithtrimcapsandcarefullytuned
3)W2,12.5kHzbandwidthmodifiedwithsurfacemountcapacitors
4)W2,12.5kHzbandwidthmodifiedwithdiscceramiccapacitors
5)GenuineUW,12.5kHzbandwidth,nomodificationsneeded.
6)GenuineW1,25kHzbandwidth
7)GenuineUW,25kHzbandwidth
8)W4,25kHzbandwidth,modifiedwithanycapacitor
ProgramminghighpowerforUHFCBfrequencies.
Note:doingthisisverynaughty! Itis,infact,illegal. But,itispresentedtoyouherefor'educational'purposesonly. Besides,giventhattheprocedureissimilartoprogrammingoutofbandfrequenciesasabove,itprobablywouldn'thavetakenyoutoolongtohavediscoveredthistrickanyway. Letspresson.
Justliketheprocessforprogrammingoutofbandfrequencieslistedabove,youcanreadtheconfigurationfromyourradio,disconnecttheprogramminginterface,thenusingFPPchangethehardwarecodetoasimilaronebutinaVHFA9bandunitthathas25wattsasstandard,andtheneditthechannelsforhighpower,leavingthefrequenciesandeverythingelsealone. Thenchangethehardwarecodebacktoyouroriginalcode,andyouwillseethatyourUHFCBfrequenciesarenowavailablewithhighpower. Donoteditanythinginthechannellistafterthispoint. Saveyourhighpowerconfigurationtodisk,andthenwriteittotheradio. Don'tforgetthathighpowerTXismoredemandingofyourpowersupplyandofTXVCOfiltertuningoftheradio,sobesurethatboththeseareasarespot-onandfullytestedstablefirst,especiallyifyouhaveonlybeenoperatingyourradioat5wattsbeforehand.
Whenadjustingthepoweroutputoftheradio,R581setsthe'high'powersetting,normally25Watts,andR578setsthe'low'powersetting. MakecheckanyadjustmentstwicebecausethereissomeinteractionbetweenR581R578. Donotadjusttheradioformorethan25Wattsoutput-theunitwilllastlongerifyoudo. Ifyoutendtowafflealot,thenI'dsuggestthatyoubacktheoutputpowerdownto15Watts. Ofcourse,ifyouwishtoremainlegal,thenthereisnothingtostopyoufromsetting'high'powerat5Watts,and'low'powerto1orlesswatts,andyourradiowillbeabletotransmitatthesepowerlevelsnearlycontinuouslywithoutbeingstressedatall. Itisamazinghowfareven100mWwilltravelgivenagoodantennacoax. Notethatthetransmitarrowwillceasetolightupbelowabout500mW,buttheradioisactuallystilltransmitting,ifyoudecidetosetthepowerthatlow. IfyouwishtoprogramhighpowerforUHFCBonthe8010or8020,justenterthepowersettingto"H"-that'sit. Theprogramdoesn'tcomplainatall,strangelyenough!
Programmingin12.5KHzstepchannelsona25KHzradio:
Nomatterwhattheband,justenterthe12.5KHzstepfrequencyasyoudesire. Itwillwork! Notethatthisdoesnotmagicallynarrowyourreceivefiltertosuit12.5KHzchannels,norwillitdecreasethedeviationtosuit12.5KHzchannels. Tobetransmittingonsuchchannels,youwillneedtoreducethedeviationtosuitthenarrowerbandwidthsinvolved. Forreceive,eitheryoucanputupwithreducedadjacentchannelrejection,orreplacethefilterstosuit. Andyoureallyshouldgetahigherstabilityreferenceoscillator,too. Thisisnotaneasyjob!
Conversely,ifyougetyourhandsonaradiounitthatisintendedforoperationon12.5KHzchannelsandwanttouseiton25KHzchannels,youwillneedtoincreasethedeviationsothatyoudon'tsoundsoquiettoeveryoneelse. Strangely,the12.5KHznarrowfiltersdon'tseemto'clip'thewider25KHzchannelsonreceive,butifyoucomeacrossasignalthatisnotdead-centreonfrequency,thatsignalwillsoundscratchy(commononUHFCBwheretheoperatorhasblindlyadjustedeveryadjustmentincludingthefrequency'netting'inanattempttogetmoreRFpower/deviation/everythingelse). Andhavingthehigherstabilityreferenceoscillatordoesn'thurtonelittlebit. Thereareotherdifferences,butthesearesominorthatyoushouldn'tbeconcernedaboutthemwhenusinga12.5KHzuniton25KHzchannels.
Othermods:
Thereareothermodsthatyoucandothathavenothingtodowiththeradiosideofthings. Youcanmodifythedisplaybacklightcolourbyeitherchangingthelightbulbswithin(theprettycoloured1.5voltgrainofwheatbulbsfromDSECat.P8120-P8124aregood,butmakesuretouseacurrentlimitingresistor-Isuggestatleasta68ohmresistorforthetwobulbsinserieswhenpowereddirectlyfromthebacklightswitchingtransistorsupply,otherwiseyouriskburningthebulbsoutprematurely)orbyremovingtheexistingbulbsandapplyingathincoatofpaintofyourownchoice. Greenlooksnice,asdoesblue.
ThereisamuchbettermodificationforthedisplaybacklightcolourdetailedatthePRM80-seriesyahoogroups,thisuses3mmblueLEDs.Takealookat:

YoucanalsoaltertheLEDbacklightsofakeypadmicrophone-justobservethepolaritycarefully. Theuseofdiffused,standardoutput(ienotthesuperbright,narrowbeamtypes)LEDsworkbest. Ichosetokeepthestandardgreen,butblueLEDslookgood,too,andIimagineyellowororangewouldbequiteOK,too.
Ialsofoundthattheminimumvolumefromthespeakerwastoohighforaquietenvironment. Therearetwomethodsaroundthis-oneistoplaceanattenuatingpadbeforetheaudioampinsidetheradio,butmypreferredmethodistouseapadinlinewiththespeakeritself. Thatway,youcanquicklyremovethepad(whichcanbeassimpleasa27ohm5wattresistorinthehotaudio line)ifyouneedto. Oryoucansimplyuseasmaller,lessefficientspeaker,butthesedon'tsoundasnice. Bytheway,Ialsoreplacetheaudioconnectortoastandard3.5mmaudiosocketplug,whichmakesiteasytochangecomparespeakers.
Ifyouareremovingthemikecoverconstantlytoexperimentwithreprogrammingtheunit,youmightwanttouseapairofsharpdiagonalcutterstoremovethetabthatlocksthemikecoverinplace. Thismakestheremovalofthecovereasyusingjustfirmfingerpressureratherthanhavingtoresorttoasmallscrewdriverallthetime,andthecoverwillstillremainfirmlyinplaceduringnormaluse. Awordofwarninghere:constantlyreprogrammingyourradioisnotagoodidea. Apparentlythereisafinitelimittothenumberoftimesaradiocanbeprogrammed;oneunitIwasplayingaroundwithwasworkingfineandIwantedtomakeonesmall,finalprogrammingadjustment. Oncethatwasdone,theradioneverworkedagain,emittingaconstantbeep-boop,anditwasn'tduetomis-programminginanyway. FaultfindingindicatesacorruptedEEPROM,whichcanberecoveredbyusingspecialsoftwarewhichIcannot'giveout'-youwillneedtoemailmeifthishashappenedtoyou. Sobewarned! Themoreyoureprogramtheradio,themoreyouruntheriskofsomethinghappeningthatcorruptstheEEPROM.
ThevolumeknobofthePRM80shasnopointeronitforyoutoseeroughlywherethevolumeissetto-whichisofcourseveryeasilyrectifiedbyadotofpaint,asmallsticker,orremovingtheknobandcuttingafinenotchinitwithafinefileorhacksaw.
Customcreatingalabelforyourdefinablebuttonsiseasy-justfiddlearoundwithyourchoiceofwordprocessortocreatealabel,printitout,andfititundertheclearplasticbezel. Youwillneedtofiddleheapstogetthespacingright,buttheendresultlooksgreat,andisverypracticalindeed. Alaserprinterproducesthebestresults.
Ifyouliketowafflealot,youwillfindthattheheatsinkwillwarmupconsiderablyevenonlowpower. Thiscanberemediedbyusingasmall12voltCPUfanfittedtotheheatsink. Useapairifyouarereallyworried. I'venotdonethistomyunit,andsohavenotexploredhowtoaffixthefanstotheheatsink. Maybeacustommadebracketcouldbemadeup,orsomeothercowlingorthelikecouldbefashionedfairlyeasily.
Ihavenotinvestigatedthisnext'modification'-Ihaveheardthatthe64channelPRM8020scanbeprogrammedwithmorethan64channels. Thisdoesn'tsurprisemesincethePRM8030normallycanonlyhave100channels,butwiththeV4'Xtra'versionofFPPyoucanuseupto160channels-apparentlyachievedbysacrificingmemoryusedforholdingvotingchannelsfor'normal'channels. HowdoesoneachievethistrickonthePRM8020? Iwouldn'tknowmyself,butitprobablyinvolveshackingintothebinaryimagethatgetswrittentodisk,andaddinginyourextradata,andthenwritingthisbacktotheradio. Thebinaryimageforthe8020isimpossiblysmall,andwhenIexaminedit,Icouldn'tseeany'idle'datatofillintogaintheextrachannels,butthenagainIgaveupmachinelanguageprogrammingsome10yearsago-it'sgoingtotakebettermindsthanminetofigureitout. LikeIsaid,Icanonlytakesomeeducatedguesses,butIhaveheardfromareliablesourcethatitcanbedone. Ifanyonehashardinformationonif/howthisisdone,pleaseemailmeandletmeknow.
Morethan10channelsforthePRM8010?
I'venottriedthis,butothershaveandtheysaythatthisworkswell.IfyouhavealatermodelPRM8010withaversion2controlboard,youcanreplacethehead/displaywithaPRM8020type,thenreprogramthehardwareasaPRM8020andeffectivelyturntheradiointoa8020,thenreprogramthesoftwaresideofthings,completewith64channels. Tocheckifyouhaveaversion2controlboard,lookforIC203,theEEPROMthatstoresthechannels. IfthisICisaNMC93C566(8kmemory)thenyouareinluck,thismodificationispossible. IftheICisaNMC93C556(2kmemory)thenyouareoutofluck. Itwouldappearthatradiosproducedaftertheearly1990shadthe8kchipinthem.
AligningthemuteforthePRM80series:
Thisadjustmentcanbeverycritical:getitwrong,andyourmutewon'topenuntilasignalislargelynoisefree. Getitright,andthemutewillopenonveryweaksignalsindeed,althoughyourresultswillvaryslightlyfromunittounit.
Firstly,setyourmutetolevel02-thisisveryimportant. ThenadjustR455anti-clockwiseuntilthemuteopens,andwhitenoiseisheard. Then,VERYslowly,turnR455clockwiseuntilthemuteclosesagain,andstopthere. Ifyouregularlyoperateyourradioinextremesoftemperature(inacar,forexample),thenyouwillfindthatyouwilleitherhavetooccasionallyoperateyourmuteat04levelorevenhighertomutereliably,orintheabovetuningprocess,advanceR455onlyslightlypastthepointwherethemutecloses,andsacrificesomemutesensitivity. Thereasonforthisisthemutenoiseampisslightlytemperaturedependant-heatseemstocausethemutetobecomereluctanttoclose.
Settingthemuteusingtheseinstructionsproducesaverysensitivemute,andmaynotbesuitableforoperationinahighnoisefloorenvironmentsuchasinSydneyorMelbourne. Ifyoufindthisisthecase,youwillneedtosetthemuteat04or06orevenmoreinFPPasyourdefaultsetting. Thatwayyoucanstillhaveaverysensitivemuteifyouneedit,butundernormaloperation,themuteshouldbehaveitself.
SelCall(SelectiveCalling)decodewiththePRM80series:
SelCallisasystemwhereyoucanmuteyourradioandkeepitquietevenwithmultipleotherusersonthesamechanneluntilyouarecalledbyanotheruserwithyourSelCallnumber. Thenyourradiowill'un-quiet'andyouwillbeabletohearyourcaller. ThisfeatureiscommononUHFCB,andissometimesusedon'real'two-wayradionetworks. AsimilarfeaturecalledANI(AutomaticNumberIdentification)sendsaSelCallburst,morecorrectlyknowninthisinstanceasanANIburst,toidentifywhoiscallingeachandeverytimethePTTispressed.
ThePRM80seriesiscapableofbothSelCallandANI,andifconfiguredprogrammedcorrectlyiscapableofdisplayingreceivedSelCallandANInumbers. Beforeyougettooexcited,youwillneedaPRM8030or8025,anditispreferabletohavea6digitdisplaytype. Infact,SelCallwithonlya4digitheadisapaininthebum! Youcansendfixednumbersbuttosendvariable(ieuserentered)numberstakesalotoffiddling,anddecodedisplayrequiressomespecialtricks. SelCallbecomesmucheasierwitha6digitheadandmatchingcontrollermike. ThiscombinationonlywillallowyoutodirectlyenterSelCallnumbers,anddecodedisplaynumbersdirectlytothedisplay. Justincaseyouwerewondering,theDTMFmike(theonewiththeLED)cannotbeusedforSelCallentryoneither4or6digitheads-onlythecontrollermikeiscapableofdoingthis. Infact,thecontrollermikewillnotreallyworkasacontrollermikeon4digitheads-itcanreallyonlybeusedasastandardmike. Sopracticallyspeaking,it'sa6digitheadandcontrollermikeornothing,sofarasSelCallisconcerned. VerylimitedSelCallfunctionalityisavailableto4digitheads.
(thisnextsectionwillbeofmostvaluetothoseinterestedinusingSelCallontheAustralianUHFCBband-readersfromothercountriesmaywishtoskipthissection)
WhenaSelCallsuitableforUHFCBissent,itissentusingtheCCIRformat. ThereareminorvariationsinCCIRformat,butthesedonotmatterhere. TheoldestSelCallschemessendonlythenumberbeingcalled,usuallyafivedigitnumber. Newerschemessendaninedigitnumber,thefirstfivenumbersbeingtheradiobeingcalled,withthelastfourdigitsbelongingtotheradiodoingthecalling. Withthisscheme,theSelCallnumbersusuallystartwitha1ie15678. Thatisthereasononlyfourdigitsofthesendingradioissent-youcanassumethe'missing'firstdigitisa1. Theverylatestschemesuse10digits-thefirstfivebeingtheradiobeingcalled,andthelastfivedigitsbeingtheradiodoingthecalling. UHFCBsthathavea10digitschemeoftenhavethecapabilitytochangethefirstnumberoftheirSelCallidentity,soyoucannolongerassumethatthefirstdigitisa1.
Sowhywasthisshortexplanationneededhere? ThePRM80SelCall/ANIdecodefeatureismostusefulwiththe5or9digitformat,wherethefirstnumberofaSelCallidentityisusuallya1.
ToenabletheSelCall/ANIdecodingfeature,youwillneedtobecomeamemberofyahoogroupsontheinternet,andonceyouhavesignedupasamember,specificallythe"PRM80-Series"andthe"AustralianPMR"groups,youwillbeabletodownloadaversionofFPPcalled"version4extra"from

Thisisnotan'official'releaseversion,andassuchisnotsupportedbyPhilips/Simoco. Youcanalsofindthissoftware,andaDIYprogrammingleadat:
Onceyouhavethisversion,openthe'master'configurationfile,andenteryourdesiredpersonalityfortheradio. Onthe'SelCalldecodeoptions'page,youcanenteryourindividualidentityifyouwish,andthenkeep(orchangeifnecessary)thegroupdecodeto1vvvv(or3vvvvorwhateverfirstdigitsuitsyourrequirements). Youwillneedtostartfromscratchusingthis'master'file,as'reading',editingthen'writing'yourpresentconfigurationdoesnotwork,asIhavefoundout. Youmaywanttoalsoprogramafunctionkey(ifyouhaveonespare)as'GroupSelect'whichwillona6digitdisplayshowthelastnumberdecoded. Notethatthenumberdisplayedisinmostcasesthe'called'identity,anditwillonlybedisplayedforabout6seconds. Thereisanexceptiontothis:iftheselcallbeingsenthas10digitsandboththecalledandcallingnumbersbothstartwitha'1',thenthePRM80willdecodethefirstfivedigits(thecallednumber)anddisplayitverybriefly,andthenreplaceitwiththenext5decodeddigits(thecallersnumber).
Ifyousetthedecodeidentityto1vvvv,itwillofcourseonlydisplayidentitiesstartingwitha1. Ifyoutrytouseamasterfilethathasalldigitsasvvvvvthenthedecodefeaturedoesnotworkproperly. Ihavetriedseveralotherconfigurations(ieFvvvvv,1Fvvvvvetc)totrytodecodeallfive'calledidentity'digits,butbelieveme,1vvvvistheonlymethodthatworksproperly.
Anotherbenefitofusingthisprogramistheabilitytoprogram160channels,althoughthechannelsabove99aredisplayedontheLCDashexadecimal. Ifyouarehandywith'hexedit'typeprograms,youcanwritechangestothe'master'filethatyounormallywouldn'tbeableto,suchasthedecodeidentityofvvvvv. (Rememberthatevenusinghexedit,vvvvvstillwillnotwork...)
Irecommendusingalaterfirmwareversionofyourradioforthesefeaturestoworkproperlywiththe'extra'versionofFPP. Itriedtouseanearlyversionfirmware(V2.11,singlemodeunit)andfoundthatthemutesettingoperationwasstrangeindeed,aswellassomeotherquirks. Also,lock-upsanderraticoperationwasnotedwithversion4.6firmwareondualmodeunits. Theverylatestfirmwareversionsasat13/3/2001are:
SingleMode(PMR)-Version3.95(3502-362-06539.5)
DualMode(MPTversion)-Version5.0(3502-362-07195)
DualMode(ANNversion)-Version1.8e(3502-362-07202e)
Incaseyouwerewondering,theMPTisbyfarthemostcommontrunkedversionofthedualmoderadios. ItisinterestingtonotethattheV5.0MPTdualmodefirmwareincorporatesV3.81PMRfirmware,whichisnotthelatestversionforPMR. OnethingtonotewithV3.95PMRfirmwareisthatyounolongerneedtoprogram'keypadmodeselect'toafunctionbutton-usethekeysequence:digit-star-digit. Forexample,ifyouprogrammedRSSIon/offaskeypadfunction9,thentoturnitonwithoutusingtheusual'mode'untilyougettheflashing'F'andthenpress9,youpress9*9. Thiswillsaveyoufromhavingtouseupanextrabuttonasthe'mode'button,butonlyifyouwantjustthekeypadfunctions. IfyouwanttousethekeypadforSelCallentryorDTMF,thenyouwillstillneedtoassignabuttonontheheadfor'mode'select.
Ihaveuseddualmodefirmware4.7andsinglemodefirmware3.6withoutproblems,soIwouldsuggestthatyougetatleastthesefirmwareversionsasappropriate. Ihaveprovidedtheseversionsoffirmwareasbinaryimagesfordownload,aswellastheverylatestversions. Justlookwhereyoudownloadedthiswordfile(lookfor"8030firm.zip"whichdespitethenamealsohasfirmwareforthe8025).IhavefoundthatV4.7(dualmode)andV3.6(singlemode)tobereliableenoughformypurposessofar. Byallmeanshowever,tryusingthelatestversionsifyouwant.
Notethatyoucannotputdualmodefirmwareinaunitthatwasadedicatedsinglemodeordedicatedtrunkingunit,evenifyouchangethe0ohmjumpersunderneaththeEPROM-theEEPROMICwillnothavesufficientmemory.
ItisalsopossibletodisplaySelCallnumbersonfourdigitheadsusingthe'GroupSelect'feature-sometestingIhavedoneshowedthatthefourdigitheadswereabletodisplaytworeceivedSelCalldigits,andthatusingthe'GroupSelect'buttonyoucanviewtheothertworeceivedSelCalldigits,butyouneedtodisableorturnoffanyotherfeaturethatusesthetwosmallerdigitssuchasRSSIfirst.
Someotherparametersthatmaybeofinterestisthat,normally,SelCallonUHFCBconsistsofthefollowingparameters:
Tonelength:40msLeadinTone:1LeadinTonelength:400ms
(actually,thereisalsoa40msgapofsilencebetweentheleadintoneandtheselcalldigits-usetone'F'tosendsilenceduringthesequence-butmostradioscancopewithoutthissilenceperiod,sosendingofSelCallsentereddirectlyfromakeypadcontrollermicrophoneispossible-youcan'tsend'notone'ortone'F'usingthekeypad,butyoucanprogramittoapre-assignedsendidentityinFPP) CMLCCIRformatasusedbythePRM8030isthemostcompatibleformattouse. Ofcourse,thePRM80istheultimateinconfigurableUHFCBradios,soyoucandosomeprettyperversethingswithSelCall..!
Anothertrickthatsomeonehasdiscoveredisthatyoucan'group'call10000SelCallidentitiesallatoncebysendingsomethinglikeF1AEAExxxx,wherexxxxisyourcallingidentity. YoumustprogramthisasapresetSENDidentityalongwithaleadintoneof1. (justliketoneF,youcantsendtoneA,thegroupcalltone,fromthekeypad,whichiswhyyouneedtoassignittoapresetsendidentity) ThisworksforanyonewhohasaSelCallcapableUHFCBthathasgroupcallfacility,andtheyhavenotdisabled'groupcall'facilityintheirradio.
Anothertrickthatcanconfuseothersoutthereistosetthe'acknowledge'numberto1vvvvwithadelayofabout2seconds. Doingthis,coupledwiththeabovedecodedisplayfeature,willcauseyourPRM80tore-sendaSelCalltosomeoneelsewhohasjustthemselvesreceivedacall. Useless-yes. Still,itisanotherfeaturethatisonlymadepossiblebytheultra-flexibleSelCallschemeintegratedintothePRM8030.
WhenfiddlingwithSelCallonthePRM80FPP,neverusethe'Validate'feature(F8key)-thiscanmessupyoursettingsandyourSelCallmaynotoperateasyouexpect.
ConvertingadedicatedtrunkingunittoaPMR"normal"unit:
ByremovingthetrunkingfirmwareEPROMandreplacingitwitha'singlemode'PMRfirmwareEPROMandthenresettingtheRAMandreprogrammingtheunitwithyourrequiredinformation,youcanconvertadedicatedtrunkingunittoaconventionalPMRunit. Youmight(notalways)needtofiddlewithsome0ohmjumperslocatedundertheEPROMtogetthingsgoing(removethetwosidebyside0ohmjumpers,andre-installone0ohmjumpertothepairoflandsnearpin1oftheEPROM) Youmayalsoneedtolookatinstallingsomemore0ohmjumperstorestoreSelCall(R338andR946-bothlocatedjustslightlytothefrontoftheFX439offeachfrontcornerofthatIC)
ThereissupposedtobesomerecentversionsofFPPforthetrunkingseriesofradiosthatallow'conventional'ornormalPMRchannelsinthetrunkingradios. Ihavenottriedthismyself,butitprobablywouldbeagoodshorttermalternativetofirmwarechanging. FullPMRfunctionalityisn'tavailablethroughthismethodandyouonlyget32channels,butatleastyoucouldgettheradioupandrunningonyourdesiredchannels.
An8030Tcanbeconvertedbyeitherusinga8030singlemodeEPROMor8030dualmodeEPROM. Again,youmighthavetofiddlewith0ohmjumpers. Ifconvertingtoadualmode,leavethetwosidebyside0ohmjumpersinplace,andinstallanewonetothelandsthatarelocatednearpin32oftheEPROM. Itwouldbesafer,however,totrytokeeptheunitusinga512kEPROMbyusingasinglemodeEPROM,andprogrammingtheradioaccordingly.
ThePRM8025T(forsomereasonlabelled8020T,butwhenyouopenitup,itlooksjustlikean8025)canbeconvertedtoPMRmodebyobtainingthe8030PMRfirmwareandloadingthisontoa512kEPROMandusingthis. Inmyexperience,Ihaveconvertedthree8020TstoaPMRunitbyusingthe8025/8030singlemodefirmware,butadisplaychangeisnecessary. Youneedtoeitherfinda6digitlocaldisplayunitanddiscardthetrunkingonly4digitlocaldisplayunit. Oryoucanprogramtheunitasan8030remote,andchangesomecomponentsaroundtoacceptagenuineremotehead(4or6digitremoteheadPMRdisplayunit). Inotherwords,youperformalocaltoremoteconfigurationmodification,andyoualsodothetrunkingtoPMRconversion. Thelocalheadisdiscarded,andaremoteheadreplacesit.
Itisnotpossibletokeeptheoriginal4digitdisplayunitfromatrunkingunit(either8020Tor8030T)andhaveitworkunderPMRmode. However,some8030Tsdidhaveheadsthatwouldworkeitherway,butmanydidnot.
ImprovingtransmittedaudioonthePRM80series:
WhenIhadaFM91,IfoundthatthestandardmicrophonesoundedOKwitheveryoneelse'svoiceontransmit,exceptmine. Forwhateverreason,myvoicetookonagravelly,harshquality. Thefixwasdeceptivelysimple-replacethestandarddynamicmicrophoneinsertwithanelectretcondensertype. IfoundasimilarthinghappenedonsomePRM80units,andthefixagainwasthesame. Replacingthestandarddynamicmicrophoneinsertwithanelectretcondensertypeiseasy,justmakesurethatyoubiasthepositivesideoftheelectretcondenserinsertviaa100kohmtrimpotfromthe+8voltsupplythatyouwillfindinsidethemicrophonepreampboard,andpassthesamepositiveconnectionfromtheelectretinsertviaa0.01to3.3uFtantalumcapacitortothe'hot'sideofthemicrophonepreampinput. Yourchoiceofcapacitorthatyouusewilldependonhowmuch'bass'youwantforyourtransmittedaudio-thehigherthevalue,themoreemphasisonbasstherewillbe. Thiswillalsobedependantontheelectretinsertitself. Experimentwiththisvaluetoreachthebestqualityforyourvoice. Ifyoufindthestandardmicrophoneworkswellforyou,thenthereisnoneedto,norrecommendedtodothis. Ihavealsofoundthestandardmicrophone(ienon-controller,non-DTMF)soundsbetter,too,sotrythisifyoudonotneedtheextrafunctionsofferedbymicrophoneswithakeypad. Youwillnevergeta'hi-fi'soundlikethatoftheSawtronrangeofradioswiththePRMs-theyfilterthetransmittedaudioveryheavilyindeed-300or500Hz(dependingonCTCSSinstallation)to2550Hzforthe12.5KHzradios,or3000Hzforthe25KHzversions. Comparethiswith100Hzto5000HzforatypicalUHFCBwithoutCTCSS.
Anotherproblemthatisnoticedisanaudible'tick'ontransmiteverytwosecondsfortheremoteheadmodels. Thisiscausedbythedatalinesontheremotecable'crosstalking'intotheaudioline. Asolutionistokeeptheremotecableasshortaspossible,whichofcourseimpliesacustommadecable. Anothersolutionforthosewhocan'tavoidlongcablerunsistoreplacetheaudiolineoftheremotecablewithashieldedone. Thediagrambelowwillshowyouwhichconductortoshield. Again,acustommadecableisrequired. Thesetwosolutionsdon'tentirelyeliminatetheproblem,butcanmakethe'tick'almostimperceptible.
Basedonthediagramabove:
Pin1:Transmit(microphone)audiofromheadtotransceiverbody
2:Ground
3:Lowlevelspeakeroutput
4:+9VoltsDC
5:Micground(sameaspin2)
6:On/offcontrol
7:RXdataintotransceiverfromhead
8:TXdatafromtransceivertohead
Pleasefollowthepinoutsabove,onwhichIhavebasedmytableabove. Ihavesearchedhighlow,andnotfoundadefinitivepinoutfortheRJ45connector. ForeverydiagramIfound,Ifoundanotherthatwastheopposite. Whoeverisrightorwrong,Ihavebasedmyfindingsonthediagramabove. Notethatthesepinoutsarefortheremoteinterfacecablegoingbetweenheadbodyoftheradio,NOTthemicrophoneconnector.
Toreducethe'tick'inducedintothetransmitaudio,shieldthewirethatconnectsto'pin1'withtheshieldconnectedto'pin2'. Onlyshieldthemicrophoneaudiowirebyitself. Donothavetwoearthpathsviapin2(possiblycreatinganearthloop). Youcouldtryusingpin5astheshieldearthinsteadofpin2ifyoufindpin2doesnotproducesatisfactoryresults.
Anotherpossibilityistousea'straightthru'RJ45twistedpairLANpatchcableWITHOUTanycrossovers. Unlessyouknowforsuretherearenocrossovers,donotusethissortofcable,asdamagetoyour8030willresult. Thiswillnotbequiteaseffectiveastheabovemethods,butdoesgivesomeimprovementatleast.
AddinginascramblerintothePRM8030
AddingascramblertothePRM80isaninterestingexperience. Thereisprovisionforaccesstothetransmittedaudiobeforepre-emphasisandtoreceiveaudioafterde-emphasisvia0ohmresistors(oneontopofthecontrolboard,oneunderneath). Thereceivedaudiolevelatthispointisfairlyhigh-6voltspeaktopeak,soyourscramblermustbeabletohandlethathighlevel,oruseadividertoattenuatethelevelintothescrambler,anduseanop-amptoboostthelevelbacktotheoriginal. Thepointsare:R952forTXaudio(inputtoscrambleronthelegtowardsthefrontoftheradioboard,outputfromscramblerconnectstothelegthatisclosesttheERPOM),andR227BforRXaudio(inputtoscrambleronthelegtowardstherearoftheradioboard,outputfromscramblerconnectstolegtowardsfrontofradioboard). R952isa0ohmresistorthatislocatedonthetopsideofthecontrolboard,nexttoR322(micgainadjustment)andR227Bisa0ohmresistorontheundersideofthecontrolboard,nearwherethe5voltregulatorisconnectedtotheboard. OnceR227Bisremoved,theaccesspointsforthisresistorcanactuallybefoundonthetopsideoftheboard,makingscramblerattachmentreasonablyeasy. Obviously,youneedtoremovethese0ohmjumpersto'break'theaudiopathandrouteitthroughyourscrambler.
However,thepreferredaccesspointsareafterpre-emphasisfortransmittedaudio,andbeforede-emphasisforreceivedaudio. Thisispreferredtogivebetteraudioquality,andisvitalforanyunitsthatusedigitalsignalling(syncsignals)ortruedigitalmodulationmethods. (Truedigital? Wow,you'vefoundaprettyhighendscrambler!) Theaccesspointsherearenotsoconvenient,bothbeingontheundersideofthecontrolboard,andbothpointsneedtohavetrackscutorsurfacemountcomponentsliftedtobreakthepathsforaccesstotheaudio. Thepointsare:betweenR377B(a4.7ksurfacemountresistor)andR325B(a680ksurfacemountresistor)forTXaudiowiththeinputtothescramblerfromR377BandoutputfromthescramblergoingtoR325B. Obviously,youneedtocutthePCBtrackthatjoinsthesetwocomponents,whichcanbefoundontheundersideofthecontrolboard,neartheremoteinterfacesocketonthePRM8030. ForRXaudio,youneedtocutthePCBtrackthatjoinsR216B(a10ksurfacemountresistor)andC214B,withtheinputtothescramblerbeingfromR216BandoutputfromthescramblergoingtoC214B. Thesecomponentsarebothlocatedontheundersideofthecontrolboard,nearthesurfacemountICLM2904whichistheICclosesttheinputDCpowerconnector.
Gettingthewirestotheseaccesspointsfromthetopsideoftheboardwherethereisroomtomountthescramblertotheundersideoftheboardwhereyouconnectintotheradiocircuitryisbestachievedbyroutingthewirestotheundersideoftheboardnearorbetweenthevoltageregulators,andifnecessaryfilingasmall'channel'intheshieldingridgesofthechassisforthewirestofitthroughtoaccesstheareaoftheboardthatyouneedtoconnectinto. Itwillallbecomeclearonceyouremovethecontrolboardtoaccessthepointsontheundersideoftheboard. Alittlebitofdoublesidedtapewillhelpkeepyourwiringforthescramblerinplace. Seephoto8030DMCR.jpgtogetanideaofwhatthisisallabout.