[Milsurplus] re SCR-522 ( Milsurplus Digest, Vol 137, Issue 35 )

[WA5CAB--- via Milsurplus]

Yes, that's partially true.  The multiplication factor is 18 (tripler, 
tripler, doubler) for the BC-625 transmitter but varies from 11 to 18 for the 
BC-624 receiver.  However, the set did not use FT-243 crystals .  I don't 
recall ever actually opening up any of the ones that it did use but suspect some 
of them at least may have been made like the FT-241.  But in any case, the 
same would apply to the other three VHF aircraft sets that were available 
during all or part of the period (AN/ARC-4 and in the latter part of the War, 
AN/ARC-1 and AN/ARC-3).  Having a little experience with all of them on the 
ground, I can say that the autotune mechanism in the BC-624 and BC-625 is at 
best "fiddly".  

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 09/23/2015 01:18:42 AM Central Daylight Time, 
neilb0627 at gmail.com writes: 
> As I recall, a great deal of multiplication was needed to get from
> crystal frequencies in the low HF region to 120 MHz or so. Something
> like 18 or 20 times multiplication. The crystals in those days
> consisted of a quartz sheet clamped between two plates.
> 
> Such crystals can be very stable at ground level in a moderately
> temperature-regulated operating room, but take them up a few thousand
> feet and watch them shift. 500 Hz shift at 6 MHz becomes 10 KHz shift
> at 120 MHz.
> 
> 73 de Neil ZL1ANM
> 
> On 9/23/15, WA5CAB--- via Milsurplus <milsurplus at mailman.qth.net> wrote:
> >Probably tuning (xmtr power out and rcvr sensitivity) drift rather than
> >frequency drift.  Although the typical 60 to 140 F temperature variation
> >would
> >shift the crystals slightly, too.  No ovens in the SCR-522 or 542.
> >
> >In a message dated 09/22/2015 23:16:50 PM Central Daylight Time,
> >kargo_cult at msn.com writes:
> >>>Bruce Vaughn/NR5Q (SK) was a USAAF radio tech in the ETO.  He told me
> >>that
> >>>the SCR-522-A was easily the most important and most used USAAF radio 
> set
> >>>
> >>
> >>>in the ETO.  But Bruce complained of its drift with temperature
> >>>change...
> >>
> >>Mike, how explain this? The set was quartz-controlled both r and t, and
> >>the
> >>IF surely wasn't that selective, right?
> >>-Hue
> >
> >Robert Downs - Houston
> >wa5cab dot com (Web Store)
> >MVPA 9480