[MRCA] PRC-127

[Ray Fantini]

I would have thought that somebody on here was familiar with the 127 being it's a fairly common radio, and maybe they would know what the reference oscillator is set to and what frequency it should be. Don't know about that radio but have worked on several things where everything is packed tight but perhaps you can look around and see what's in there. Any crystal oscillator will have its frequency stamped on it and there may be some form of a compensating capacitor to correct it?
RF

From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On Behalf Of Robert Newberry
Sent: Tuesday, July 30, 2013 9:29 AM
To: mrca at mailman.qth.net
Subject: Re: [MRCA] PRC-127


My freq counter says at 136.000 programmed. Reads 136.00199. Programmed 160.0000. Reads 160.00225.

It is also off consistently by approximately that much on all channels.

Apparare Scientior
Paratus Communicare
-N1XBM
On Jul 30, 2013 8:42 AM, "Ray Fantini" <RAFANTINI at salisbury.edu<mailto:RAFANTINI at salisbury.edu>> wrote:
Important after thought, if the radio is on channel on any channel the reference oscillator is correct! Check the error on the lowest programmable channel around 136 MHz and the highest channel 160 MHz and although the percentage of error may be different if there is no error on some channels and error on others it's not a reference problem, in that case you have a divider problem and throw the radio away! But if you see a consistent error that increases with frequency like your describing would assume that your reference oscillator is a little off.
Ray F

-----Original Message-----
From: mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net> [mailto:mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net>] On Behalf Of Ray Fantini
Sent: Tuesday, July 30, 2013 8:30 AM
To: Robert N. Newberry; mrca at mailman.qth.net<mailto:mrca at mailman.qth.net>
Subject: Re: [MRCA] PRC-127

It's pure speculation on my part not having worked on a 127 before but most synthesized radios built around that time are designed around an internal fixed reference oscillator and a programmable divider chain that controls a PLL. Being that the radio will channel and if it accepts program changes would assume that the divider chain and PLL are all working and it may just be that your reference oscillator is not on frequency. Be cautious because a small change in the reference oscillator will result in a big change in operating frequency. Al lot of stuff produced back in the seventies and eighties worked with reference oscillators in the 5 or 10 MHz range. Newer radios used sealed reference oscillators but things that old often had discreet component oscillators. But if you can enter new channels and the radio is somewhat on channel the synthesizer is working so don't mess with things like the VCO or PLL system because that will only get you in trouble, good luck.
Ray F

-----Original Message-----
From: mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net> [mailto:mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net>] On Behalf Of Robert N. Newberry
Sent: Monday, July 29, 2013 10:07 PM
To: mrca at mailman.qth.net<mailto:mrca at mailman.qth.net>
Subject: Re: [MRCA] PRC-127

I should of specified by high in frequency I mean frequency error.



On 7/29/2013 10:08 PM, fred anderson wrote:
> There is an old DOS program call ham n eggs which reprogrammed the PRC
> 127 to the Ham Band
>
>
>
> Fred KB4DMQ
>
>
>
> From: mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net>
> [mailto:mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net>] On Behalf Of Robert Newberry
> Sent: Monday, July 29, 2013 4:18 PM
> To: mrca at mailman.qth.net<mailto:mrca at mailman.qth.net>
> Subject: [MRCA] PRC-127
>
>
>
> I have a PRC-127 that is a little high in frequency. I've skimmed thru
> TM
> 11-5820-1048-24 but I didn't see anything about adjustment.
>
> Anyone know where to find adjustment info?
>
> Apparare Scientior
> Paratus Communicare
> -N1XBM
>
>


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