[time-nuts] HP 10811 Tuning Diode

David McGaw n1hac at Alum.Dartmouth.ORG
Fri Oct 19 21:46:54 UTC 2012


As I mentioned, the varactor is equivalent to the Motorola MV1650. I 
have a bunch as well left over from building VCXOs.  :-)

David


On 10/19/12 3:37 PM, Rick Karlquist wrote:
> Slightly off topic:  the oscillator transistor has some 1854-XXXX
> part number, but is actually a 2N5179 selected for some minimum
> fT at 30 mADC collector current.  When the oscillator starts up,
> before the ALC takes effect, a fairly large DC current can flow
> and some 2N5179's don't have enough gain to start oscillating.
> The startup current isn't very well controlled.  This info from
> one of the 10811 designers.
>
> I have a few 100 pF 10% glass varactors in my junk box if you
> can't get them anywhere else.  The spec is the same 2X capacitance
> from 4 to 25 V, but a different XXXX-XXXX number because of the
> 10%.  They are probably at least 30 years old!
>
> Rick Karlquist N6RK
>
>
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