[MRCA] PRC 47 Mods

[B. Smith]

I highly recommend just injecting a different IF frequency of say 497 
plus or minus a couple hundred cycles  and using a small relay to choose 
between USB and LSB. Unless you find the exact replacement filter with 
the same characteristics  as the other filter you  will have an 
unbalanced output and some serious juggling and realignment is necessary.

WB2JWU has mastered the "injection" circuit and uses a divide by 10 
circuit and a 4970 kcs crystal .  You could use other division schemes 
and other crystals of course.  An item of note, ICM crystal prices all 
most triple if you order a crystal below 4 Mc. But a crystal above 4 Mc 
is around 22 bucks.  Injection overall is the easiest way to go but you 
will have to offset your dial frequencies by the amount of IF offset 
that you select. No module alignment for the
offset is usually necessary because you are using the original filter.

  Speaking of alignment most of the 47's I have worked on had increased 
output and sensitivity if I peaked  the set for the ham bands sometimes  
15-20watts -  -   Almost 1/4 of   an S unit :-)     but it makes you 
feel better like your are really doing something kinda like meticulously 
trimming your antenna for minimum SWR.

But . . . just for fun I've attached two photos of a set that I modified 
to have both USB and LSB filters installed with dip relays switching the 
filters . As you can see it gets a little crowded.  :-)


Z







On 11/11/2013 9:17 AM, KA1LHZ wrote:
> I may have a set of the Collins filters. I bought them with the 
> mistaken idea that they could be used with my GRC-106. I found a set 
> of the '106 filters but have yet to hear from the person that has 
> them. I think they are made from 'Unobtainium' these days.
> Cheers & 73
> De KA1LHZ
>
> On 11/10/2013 05:32 PM, Tim wrote:
>> Hi - Modifying the PRC-47 to LSB is fairly simple if you can obtain 
>> the correct replacement mechanical filter that was used in other 
>> Collins equipment or the era. Web searches are your friend here.....
>> A stock PRC-47, USB, can only be used on 5357 Kc in the 60 meter band 
>> due to the frequency specifications established for operation there 
>> on USB.  Of course you can operate it USB on any ham band that it covers.
>> Some PRC-47 musings here if you get 
>> bored....http://www.n6cc.com/the-prc-47-hf-ssbcw-transceiver
>>
>> Have fun with it!
>> Tim
>> N6CC
>>
>>
>> On Sun, Nov 10, 2013 at 9:14 AM, Lou Ribble <n3od at frontiernet.net 
>> <mailto:n3od at frontiernet.net>> wrote:
>>
>>     A short answer- Yes it can be comverted to LSB. I am the owner of
>>     a PRC 47 but I will let more knowlegable members fill you in. I
>>     have not converted my unit to LSB. I have done the mod to allow
>>     fine tuning and thus get on 60 meters with the half kc split.
>>     What say you WB2JWU or K4CHE?
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