[Premium-Rx] Frequency Divider Question

[Charles P. Steinmetz]

Keith wrote:

>I am somewhat irritated by the warm up drift of my military Harris 590A,
>(R-2368) while the crystal oven comes up to temperature.
>As a non-invasive solution I would like to use an external rubidium
>frequency standard, but, the one I have here is 10 MHZ
>
>Question...does anyone know of a (cheap and/or easy) programmable frequency
>divider that could do the job? (or a fixed 10:1 divider would do too).
>Suggestions welcomed.

Here is one:

http://www.perdrix.co.uk/FrequencyDivider/index.html

I believe he sells completed boards (no enclosure).  He may sell 
kits, too.  There is also complete information to build it yourself, 
including PC board artwork, if you want to do that.  You could also 
cobble up a 74HC-series decade counter with some parallel output 
buffers on a scrap of copper clad and power it with a discarded wall 
wart.  You can let the gates do the input conversion to logic levels, 
but I always use a PNP diff pair to do the conversion because it has 
much less jitter and protects the logic from the bad, bad world past 
the input jack.

However:  Note that the phase noise of a rubidium standard is 
substantially higher than the quartz oven oscillator in the 590A, and 
the divider will add some more, so the performance of the radio in 
crowded bands will suffer somewhat.  Personally, I would not take 
that tradeoff.

I just turn mine on ten minutes before I want to use it.  If I needed 
a quicker launch, I'd either just leave it on or hack in and add 
standby power for the oven.  (I, too, am surprised that Harris did 
not power the oven continuously, or at least make it switchable so 
the customer could decide.)

Best regards,

Charles