[time-nuts] Z3801A OCXO manual trimming

Bob kb8tq kb8tq at n1k.org
Mon Mar 5 16:13:36 EST 2018


Either tear into the OCXO or go shopping for a new(er) GPSDO. The
Z38xx devices all had a lot more in common with each other than they
did differences. The OCXO design changed from the 10811 to various
more modern designs. The disciplining process seems to have remained
pretty much the same over the years. 


> On Mar 5, 2018, at 11:21 AM, Joe Hobart <nova at npgcable.com> wrote:
> Thank you, Hal, for these links and to others for your comments.
> Setting the oven temperature on a turning point appears tedious.  Perhaps there
> is enough range in the frequency adjustment to put the oscillator back on
> frequency - or close enough for the EFC to be effective.  If not, I may have to
> adjust the temperature, but time is limited.
> Some measurements with the EFC disconnected and a calibrated frequency counter:
>     9999.815  KHz  at Z3801A turn on
>     9999.9984 KHz  highest frequency seen (temperature overshoot)
>     9999.9947 KHz  approximate final frequency
> The EFC does have wide range; it can almost pull the 5.3 Hz offset onto frequency.
> Thanks again,
> Joe, W7LUX
>> Does the oscillator have an adjustment?  If so, is this somewhat accessible
>> without destroying the assembly?  Are there pictures of the oscillator
>> assembly?
> https://www.realhamradio.com/GPS-oven-journey.htm
> https://www.realhamradio.com/z3801a-turning-point.htm
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