[Milsurplus] WWII Crystal Confusion

[D C Macdonald]

Then these rigs used crystals whose fundamental was
down below 500 kHz??  They must have been HUGE!

Mac, K2GKK/5



----Original Message Follows----
From: Mike Morrow <kk5f at earthlink.net>
Reply-To: Mike Morrow <kk5f at earthlink.net>
To: Alan Tasker <atasker at ix.netcom.com>, milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] WWII Crystal Confusion
Date: Fri, 19 Nov 2004 11:31:29 -0600 (GMT-06:00)

Alan wrote:

 >... one crystal has the following marking,
 > Channel 386   38.6 MHz

That one is for a BC-684 (SCR-608/628) transmitter.
Channel frequency is 72 times the actual crystal frequency.
Channel numbers from 270 to 389
Channel number = 10 x channel frequency in mcs.
120 channels at 0.1 mc spacing.

 >The other as follows,
 >Channel 36     23.6 MHz

That one is for a BC-604 (SCR-508/528) transmitter.
Channel frequency is 54 times the actual crystal frequency.
Channel numbers from 0 to 79.
Channel number = 10 x (channel frequency in mcs - 20).
80 channels at 0.1 mc spacing.

 >1.- The BC-604/684 transmitters used crystals like this I think. If so,
 >what is the Multiplication factor?

See above.  Also, see
http://www.ai.mit.edu/~sw/html/NS1W/ft-241.html
for more good info.

 >2.- The BC-603/683 Rx were tunable, no crystals?

They were tunable, push-button car-radio-type channel selection.  No 
crystals.  Each receiver channel would be set using the crystal controlled 
transmitter signal:
BC-603: 20.0 to 27.9 mc,  BC-683: 27.0 to 38.9 mc.

 >3.- What crystals and markings and multiplication factors were used with
 >the BC-620/659/1335?

These sets used the smaller FT-243 crystals that, IIRC, controlled only the 
receiver frequency (transmitter frequency was controlled by the receiver and 
an AFC system).  I seem to recall that for the BC-1335 and -659, you had to 
subtract the IF of 4.3 mc from the channel frequency, then divide by 4.0, to 
get the crystal frequency, but I may have that wrong and I don't have my 
manuals with me now.  The actual crystal frequencies ran from about 5.5 to 
8.5 mcs.  The operating frequency was the channel number marked on the 
crystal, divided by 10.

 >4.- What were the likely radios that his two crystal would be for?

See above.

73,
Mike / KK5F