[R-390] "A" stability

[Stan Gammons]

Sounds like using an "A" for digital likely isn't going to work. I'll 
give it a try before long though. If the signals in the waterfall look 
like the leaning tower of Pisa, I'll know it's not going to work :)


73

Stan
KM4HQE


On 01/11/2018 07:20 PM, Bob kb8tq wrote:
> 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
>>
>>
>>
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