[time-nuts] RF Isolation Amplifier ...

Dana Whitlow k8yumdoober at gmail.com
Sun Oct 14 12:47:50 EDT 2018


Corby,

Now that I learn that the BFT66 is a "wild one", I'd remark that stability
is
indeed the likely issue.  I was puzzled by the presence of that capacitor in
the first place, as this circuit is clearly neither tuned nor of especially
high
frequency capability.

Could you tell us more:  what kind of maser is this, and what is the role of
this amplifier in this maser?

And if it's a hydrogen maser, why you lucky dog!

Dana


On Sun, Oct 14, 2018 at 11:41 AM Ulf Kylenfall via time-nuts <
time-nuts at lists.febo.com> wrote:

>
> The BFT66 if that is the type ( a bit difficult to read ) is a really
> "wild one" on VHF. I have used it and unless surrounded by proper
> decoupling networks in a well designed circuit it can and will oscillate.
> I would have used a spectrum analyzer to check for any
> unwantedoscillations well above this circuits operating frequency.
> And also checked with a scalar network analyzer for possibleinstabilities
> in the circuits gav vs frequency.
> Also the generation of unwanted overtones can be one causeof adding the
> capacitor where it is.
> One other peculiarity with the BFT66 is that it does not use themore or
> less standardized E-B-C pin configuration.
> One design that I came across that used the BFT66 was very difficultto
> make stable. After some time I gave up on it and replacedthe BFT66 with
> BFY90.
> Best Reagards
> Ulf KylenfallSM6GXV
>
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