[ARC5] Oscillator Stability and Old-Time gear. (Was OT: Hally Instability)

[Nick England]

Synthesized military receivers should be as good as the master crystal
oscillator which can be 3 parts in 10^11 or so (that's 0.00003 cps drift
per day at 10 mc).
I have an AN/URQ-10 master crystal oscillator which has a controlled
constant temperature oven inside of another controlled constant temperature
oven inside a Dewar flask. The result is that for 0-50 degrees C external
temp change there is less than 5 parts in 10^10 freq change (just 0.0005
cps change from 32-122 F).

Probably the best receiver with a conventional LC oscillator for the HF LO
is the National AN/FRR-24 design of 1950 or so - surely the apex of
conventional tube receiver design. The complete FRR-24 is a 4-rack triple
diversity system, but each of the 3 receivers is contained in a single rack
(88 tubes, about 700 lbs). Each frequency band has a separate sealed rack
mount unit with its own RF stages, mixer, and Local Oscillator. The chassis
is thick cast aluminum with pockets for components. The LO components are
in a separate dehumidified casting with 3/16" thick walls.
http://www.navy-radio.com/rcvrs/frr24/rest/DSC03014.JPG
http://www.navy-radio.com/rcvrs/frr24/rest/DSC03016.JPG

Here's the underside of one band unit showing pockets for antenna input, 3
RF stages, and mixer stage.
http://www.navy-radio.com/rcvrs/frr24/rest3/am453-01.jpg
http://www.navy-radio.com/rcvrs/frr24/rest3/am453-02.jpg

The book says 0.0002% freq change per degree C but I haven't ever measured
mine - that's 20 cps change per degree C at 10 mc which seems pretty high
to me. This receiver was designed for comm station RTTY use, so it would
have been in a temperature controlled environment and the sealed rack unit
temps probably varied very little once everything had stabilized - a random
breath of fresh air from an open door vs. 3121 lbs and 420 tubes.....

Cheers,
Nick England K4NYW
www.navy-radio.com

On Tue, Nov 17, 2015 at 11:26 AM, Kenneth G. Gordon <
kgordon2006 at frontier.com> wrote:

> Thank you, Bob. Lots of work and I, for one, appreciate it. I would be
> interested in some sort of comparison of the receivers in your list vs some
> strictly-military receivers some time. I suspect the military jobs would
> be,
> overall, better than the average civilian ones.
>
> Ken W7EKB
> <http://www.qsl.net/donate.html>
>