[R-390] "A" stability

[Bob kb8tq]

Hi

A lot is going to depend on how stable your shack is (temperature wise). One of the cost compromises 
on the 390’s is that the crystals are not in ovens that are matched to their turn temperature. This makes 
it very much a crap shoot when you fiddle with the ovens. They most certainly do what the spec required. 
It is unlikely that the spec was looking for much better than 20 Hz of drift. To the extent these were RTTY
radios, they were 850 shift RTTY. A drift of 100Hz or so would not have bothered anything. Yes, the world
moved on after they were designed. They hung in for quite a while ….

Bob

> On Jan 11, 2018, at 7:52 PM, Perry Sandeen via R-390 <r-390 at mailman.qth.net> wrote:
> 
> Hi.
> Wrote: Myonly real point was that the R-390 needs about a day in a typical rack tosettle down
> 
> howevermuch it’s going to settle. I have no illusion about a 390 holding 0.01 Hz for15 minutes.
> 
> 
>  
> 
> That's  true for a "stock"  "A".
> 
> 
> 
> 
> Dallas Langford did a mod to his "A" BFO and reduced its drift to less than 1 Hz per hour measured with a Rb referenced counter.
> 
> 
> 
> 
> Theoretically, one could change all the "A" ovens to proportinally controlled units and put  a buffer on the 17MHz oscillator to prevent the 1 st mixer AGC action pulling it and get some awsome frequency stability numbers.
> 
> 
> 
> 
> But then what is the end purpose to the effort?
> 
> 
> 
> 
> I guess it depends how "nuts" we are with our hobby.
> 
> 
> 
> 
> Regards,
> 
> 
> 
> 
> Perrier
> 
> 
> 
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html