[MRCA] BC-654 Crystal Question

[Al Klase]

Breck,

This design was laid down before the war started.  A lot of crystals 
used 1/8" pins on 3/4" centers.  They fit perfectly across a 5-pin tube 
socket.  They used big chunks of quartz, and US production was only 
about 100K per year.

You're right about saving quartz.  That was looking like a real 
problem.  It all came by ship from Brazil.  The FT-241's were developed 
by/for AT&T once they figured out they'd meed literally millions of 
rocks for the FM-mobile sets.  The Armstrong FM design started with a 
crystal oscillator down in the 100's of KHz range, and multiplied up to 
VHF.  The crystal itself is about 1/4" square.

Could be the FT-241 technology would not go down to 100KHz, but when you 
look at the dial on a BC-1306 receiver, 200KC is close enough.  I have 
wondered how often the assigned operating freq. was an even 200 KC to 
keep things simple.

RE: Your Adaptor - Those FT-171 banana plugs are going to be pretty fat 
for the tube socked.


Al

On 2/23/2019 1:04 PM, B. Smith wrote:
> Thanks for the info Robert.   If in doubt RTFM. As usual I am guilty 
> of not reading the manual. :-[
> Looking at the crystal socket I have to ask the question as to why the 
> designers used the 5 pin socket when they could have used a standard 8 
> pin octal socket. I assume the original design used a special crystal 
> holder the "DC-12"   that fitted the 5 pin socket. Photo of the socket 
> is below.   I will have to work on my "five minute" adapter perhaps I 
> can find a 807 that has gone South and salvage the 5 pin base. Then 
> the question of using 200 kcs as a calibration point for so many 
> different radios, BC-1306, GRC-9, ART-13 etc.  Was this 200 kcs 
> frequency chosen to make it easier for the operator to calibrate  as 
> he would not get confused with so many calibration points and perhaps 
> use the wrong one on his dial?   Or was 200 kcs utilized to save 
> quartz due to the smaller size of the actual quartz on the 200 kcs 
> rock vs. the 100 kc?
> Z
>
>
>
> On 2/22/2019 1:03 PM, Robert Downs via MRCA wrote:
>>
>> Yes. See attached photo.  And if you follow the list of superseded 
>> Stock Numbers far enough, they both end up with the same number, 
>> 2X97-200.
>>
>> I don’t know why the photo ended up attached instead of embedded.
>>
>> And it is the same crystal as ultimately used several other places, 
>> such as T-47/ART-13, BC-652, etc.
>>
>> Robert Downs
>>
>> *From:*mrca-bounces at mailman.qth.net 
>> [mailto:mrca-bounces at mailman.qth.net] *On Behalf Of *B. Smith
>> *Sent:* Friday, February 22, 2019 10:35
>> *To:* Military Radio Collectors Association
>> *Subject:* [MRCA] BC-654 Crystal Question
>>
>> Did the BC-654 use the same 200 kcs crystal that was used in a 
>> BC-1306? An adapter utilized? Ebay photo below.
>> Z
>>
>>
>>
>>
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>
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-- 
Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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