[Premium-Rx] Frequency Divider Question

[Charles P. Steinmetz]

One more possibility:  I do not have a manual for the 590A, but my 
590 manual indicates that there are jumpers on the A12 Frequency 
Generator Assembly to allow the use of 1 MHz, 5 MHz, or 10 MHz 
standards.  I presume when a 590 is jumpered for an external 5 or 10 
MHz source, switching to the 1 MHz internal standard does not work -- 
you'd need to change the jumper back.

Note that the standard oscillator for a 590 was a 5 MHz TCXO -- the 1 
MHz OCXO was an option.  In my experience, most non-military 590s 
have the TCXO.

Perhaps the 590A also has internal jumpers that will support direct 
connection of an external 10 MHz standard.

All that said, I still would not use a Rubidium standard because of 
the phase noise.

Best regards,

Charles



>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
>
>
>
>
>
>
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