[time-nuts] RF Isolation Amplifier ...

Dr. Ulrich L. Rohde ka2weu at aol.com
Sun Oct 14 14:20:38 EDT 2018


Actually the BFT is out of production since quite a while there are more stable and higher Ft devices on the market. 

73 de N1UL 

Sent from my iPhone

> On Oct 14, 2018, at 12:47 PM, Dana Whitlow <k8yumdoober at gmail.com> wrote:
> 
> 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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