[time-nuts] Z3801A OCXO manual trimming

paul swed paulswedb at gmail.com
Mon Mar 5 15:56:59 EST 2018


Crazy thought.Could you just force a DC offset into the EFC assuming the
internal varicap is not out of range.
It would be simply adding a resistor to pull up or down to see if you can
get a bit of pull and allow the dac to move back in range a bit. Its a band
aid.
I know its sort of crazy. But ripping the oven apart really is no fun at
all.
Regards
Paul
WB8TSL

On Mon, 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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