>
>>>> Having designed commercial 800 MHz amps in the past, I prefer to have
>>>> them stable (as much as possible) across all possible load conditions.
>>>>
>>? However, in uhf amplifiers the anode-resonance is the tank. In hf
>>amplifiers there are usualy two resonant circuits connected to the anode.
>
>Agreed. Still you can design an HF amp to be unconditionally stable and
>test for that condition as well.
? Tuning the HF tank circuit and disconnecting the hf load have
virtually nothing to do with what is happening in the anode-resonant
circuit where the parasitic oscillations take place.
>> .
>>>And if it is with no drive applied and the neon glows
>>>orange it means it is oscillating on or near the band selected - not so?
>>>
>>? In my experiences, g-g triodes can occasionally oscillate in steady
>>state without drive above the grid self-resonance. In a 3-500Z, this is
>>approx. 80MHz.
>
>Well, then those amps have design problems. Did those oscillations that
>you mention from your experience occur with our without your nichrome
>suppressors?
? Both. Resistance-wire suppressors lower VHF gain compared to
copper-wire suppressors.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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