[time-nuts] Re: info on the 10811 used in the HP5071A

[Richard (Rick) Karlquist]

I had forgotten the details.  The schematic is indeed changed
because the trimmer is now in series with the varactor.  That
is definitely something I would do; I never approved of the
trimmer being in parallel with the varactor.  And the MVAM125
is one of my favorites.  Definitely, I am the one to get
credit or blame for this :-).  It must have "just worked"
as I like to say, because I never heard about it again.

OTOH, I have never seen a complete 10811 schematic with this
circuit.  I still don't remember having to modify the PCB/flex
circuit for this.  I am thinking they just kluged it onto the
regular one.  We would want to manufacture standard 10811's
from which ones intended for the 5071A could be selected.  Then
they would be modified with the circuit you showed.  There is
probably a drawing somewhere showing where to cut traces and
how to install jumpers to complete the rework.  Almost any
section of the 5071A, beginning with the CBT is total rocket
science compared to the tuning rework; and we only sold something
like 10 a month in those days.

I didn't know about the "wavy" ("Belleville") washers, but I
totally approve.  That sounds like something Len Cutler
would have insisted on (if so, good for him).

Rick N6RK

On 8/30/2023 1:40 PM, Corby Dawson via time-nuts wrote:
> Here is an old post showing the schematic changes required for the 10811
> oscillator modified to the 05071-60219.
> 
> https://febo.com/pipermail/time-nuts_lists.febo.com/2018-January/090824.h
> tml
> 
> Cheers,
> 
> Corby
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