Jon Ogden wrote:
>
>To me, he term "intermittent" parasitic oscillation says that the gain and
>phase
>margins of the amplifier are right on the border line. Perhaps some thermal
>noise and temperature or input signal conditions are enough to start the amp
>oscillating, some aren't. What I don't like is this idea that there are
>parasites hiding somewhere in a tank circuit waiting to jump out when you
>least
>expect them. I would call this a conditionally stable amplifier. Fixing an
>amp
>on the edge of stability is quite possibly easier than fixing one that is
>horribly unstable.
>
The ultimate test is to increase the HV significantly above the normal
voltage (which increases the gain) and look for oscillation with no load
on either input or output.
If the amp survives that test, it seems pretty certain that it will be
more-than-marginally stable at normal HV with loads on.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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