>>>Here's how I am testing:
>>>Key up amp, no RF, Ctune at min, Cload at max, open circuit on output
>>> (ie: no antenna or dummy load - no coax attached). I figured this
>>>would be worst case.
>>Sure is and not a reliable test of the amps operational stability.
? The setting of L and C-load are not substantive factors, nor is the HF
load, because L is pretty much like a vhf choke. . The resonant circuit
that supports a vhf parasite is formed by lead inductance between the
tube and C-tune, and by the anode-C of the tube.
>>Try it with real world tuning values and then remove the load.
? Transient currents are one way to encourage a vhf parasite. This
means driving the amplifier with a load connected. I would not remove
>> A good layout should then be stable.
>>In a perfect world what you are trying should work but the 4-1000A at
>>that voltage is just asking to take off, why encourage it? There are
>>even some commercial ham amps that would not pass that test.
>OK. Well, I guess I am just of the school that wants an amplifier to be
>bullet proof. Under "reasonable" real world values, I have no
>oscillation. It's just when my turns counter on my UCS-300 gets very low
>(about 5 with a minimum of 0) that I have the problem. It's probably
>barely a crank from its absolute minimum. Realistically, I'd never take
>it that low even on 10m.
? sounds like standing on thin ice.
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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