I'm pretty sure it's a classic huff and puff, nothing to do with temperature
compensation. If I remember this correctly, they work by being essentially a
frequency counter which when it sees the number changing a little, applies a
correction voltage to a varactor diode inserted somewhere appropriate in the
VFO to reverse the change. When the counter changes a lot, it assumes you
turned the knob, waits for things to settle down, then starts the frequency
counter business all over again.
Folks out here running vintage gear put them in things like Swans, notorious
for drift, and report amazing results. I haven't put one in anything so I'm
just relaying their delight.
Jon
On Jun 25, 2014, at 10:19 AM, Al Gulseth wrote:
> John,
>
> Is the VFO stabilizer a frequency reference/PLL based system or is it a
> temperature compensation type unit? I'd have to dig it out but I recall
> seeing a system (possibly in ARRL Solid State Design?) which used a couple of
> thermistors in a bridge circuit to drive a tuning diode and compensate for
> VFO/PTO drift that way. That type of compensation shouldn't cause a problem
> with an offset or RIT.
>
> If it's the former, you might take a look at the schematics for the 555 Scout
> for ideas because I think it used a frequency reference/PLL type of system to
> control the drift of the PTO.
>
> 73, Al
>
> On Wed June 25 2014 11:00:07 am John Farler wrote:
>>
>> A friend has an old model vfo stabilizer for PTO type VFO's
>> like the one in the old TenTecs. He put it on a old PTO he had
>> lying around, and amazingly, after several hours it was right
>> on within a hz or 2.
>> The question is, how would someone set one of these up for
>> an old TT, say the Triton IV, so that it would work with the automatic
>> CW off-set on xmit and the RX manual off-set?
>>
>> It would appear that the stabilizer would lock on to the new freq if
>> sending CW, since both the automatic cw off-set and the manual RX
>> offset are obtained by shifting the PTO frequency. Are we missing
>> something? Or is it for SSB only?
>>
>> BTW, I know there are newer citcuits that should work even better,
>> but wonder how they get around this seeming problem.
>> John, K4AVX
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