[ARC5] ARC5 Octal Crystals

[Mike Everette via ARC5]

The earlier version of the CFI unit in the Collins ATC/ART-13 transmitter which uses a round-case, octal based crystal actually has a 200 kc crystal in an FT-241 holder inside that round case.  The FT-241 pins are soldered into the octal base.  I've opened one up and seen it myself.

By the way, I wouldn't try unsoldering that crystal from the octal holder.  The crystal element is either welded or silver soldered to a pair of very fine wires inside the case.  After all these years, many of these crystals are prone to failure if disturbed by heat or shock.  Be Careful.

To use an FT-243 type crystal (or any other holder with the same size and spacing for the pins) in the magic eye circuit of the Command Set, plug it into Pins 1 and 3 of the crystal socket.  I have just this minute consulted the Holy Books (original SCR-274N and ARC-5 manuals) to confirm this. Works great. I have a 7000 kc crystal (marked for use in the BC-1335 transmitter) in my BC-459 to give a handy low-end band edge reference.

The ARRL-version crystal control adaptor unit was originally designed by Lew McCoy and featured in a November 1959 QST article, then in Handbooks from 1960-67 (or maybe 68).  It was something I built but didn't have great success with.  Drive to the final was low despite anything I tried.  My log filled up with one unanswered CQ after another.  I can only remember about half a dozen QSOs with that setup.  I ended up borrowing a DX-40, and made many more contacts.

73

Mike
WA4DLF

--------------------------------------------
On Sun, 8/17/14, Robert Eleazer <releazer at earthlink.net> wrote:

 Subject: Re: [ARC5] ARC5 Octal Crystals
 To: arc5 at mailman.qth.net
 Date: Sunday, August 17, 2014, 10:53 AM
 
 Perhaps we have discussed this
 subject before and I do not recall, but is it possible to
 plug an FT-243 crystal into the Command Set transmitter
 crystal sockets?  
 
 I have a BC-652-A that has that arrangement, an FT-243
 crystal rather than an octal socket crystal in the octal
 socket, even though the manual shows an octal socket crystal
 plugged in.  Robert Downs tells me this is normal, not
 a kluge.
 
 By the way, the ARRL handbook at one time had the plans a
 circuit that enabled a separate crystal controlled
 oscillator to be plugged into the 1626 socket.  In the
 old days Novices could not use VFOs.  If you wanted a
 crystal controlled Command Set transmitter, that would be
 the way to go. 
 
 Also, by the way, Gordon's article on factory built crystal
 controlled command set receivers is over at "Real Radios
 Have Motors." 
 
 And maybe someone could explain the logic of designating an
 FT-243 or FT-241 crystal the same as an FT-230 adapter. 
 
 Wayne   
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