[ARC5] bc-950 vhf TX

[hwhall at compuserve.com]

Some of the CR-1 types had removable quartz plates that could be worked like FT-243 plates to tweak their frequency. Apparently one can spot likely candidates by the way the case is assembled.http://home.earthlink.net/~navyradio/id5.html
Depending on the slab sizes (which I don't know exactly, maybe Bry Carling does), it may even be do-able to put an FT-243 slab into a CR-1 case, making finding the needed frequency simpler.  Though you'd have to relabel the FrankenCrystal case.
It looks like you want crystals for 8050 & 8089 kHz.  I have four untested CR-1/AR units that might be workable, marked: 8000, 8007.69, 8071.4, 8090.77 kHz.  Careful grinding/etching could perhaps put these where you want.  One of them has the cool circular "hatch" in the side as in the linked article.
I've been meaning to throw together a xtal test device, so if you're interested in these, I can do that & check them for activity & freq vs marking.

WayneWB4OGM

-----Original Message-----
From: Mike Morrow <kk5f at earthlink.net>
To: ka9dzr <ka9dzr at aol.com>; arc5 <arc5 at mailman.qth.net>
Sent: Sun, Nov 18, 2018 6:26 pm
Subject: Re: [ARC5] bc-950 vhf TX

> i have the BC-950A-121 vhf TX  need the Crystal for (145.600 & 144.900)
> the BC has 2 slot for the crystal holder make A&B only (B 122-156 MC
> 6777.777-8111.111) the 950 use the DC-31 type Crystal  i hvnt had
> time to see if the 950 was converted to a T-23 also any one have the
> manual for the BC-950 or T-23  thanks for any help  Dennis

If it still has a BC-950-A name plate it has not been converted.  Also, it's damned hard to miss the 815 modulator tube up front that only the BC-950-A has.

The BC-950-A transmitter uses the DC-30 crystal with thicker pins.  The DC-31  crystal holder is used in the BC-942-A receiver.  The DC-30 was replaced by the CR-1A/A, so that is what you need.  Unfortunately, you will NOT find any crystal for 145.6 MHz because the closest standard aircraft frequency of that era was 145.62 MHz using a 8090 kHz CR-1A/A.  However, 144.9 MHz was a standard aircraft frequency using a 8050 kHz CR-1A/A, so it is possible you'll be able to find one of those.

Channel A is for 100 to 124 MHz operation.
Channel B is for 122 to 146 MHz operation.
Channel C is for 122 to 146 MHz operation.
Channel D is for 132 to 156 MHz operation.

Your two frequencies could use any of channels B, C, or D.

AFAIK, there are no known surviving manuals for the VHF SCR-274-N.  It was never accepted for regular deployment.  The manual covering the T-23/ARC-5 may be downloaded here:

 http://www.radionerds.com/index.php/AN~ARC-5

You'll want AN 08-10-195 and its schematics.  BUT...as Dave Stinson and I pointed out there are many subtle and significant differences between the T-23 and the BC-950-A, especially in modulation and power connector wiring.  Dave is THE expert on those differences.

A surviving BC-950-A is sort of rare, especially compared to the much more common T-23.  It would be a shame to ham-hack one that hasn't already been violated, especially just for $hits and giggles like most such projects turn in to.

Mike / KK5F
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