>
>
>-----Original Message-----
>From: Rich Measures [SMTP:measures@vc.net]
>Sent: Friday, April 09, 1999 1:43 AM
>To: Amps Reflector
>Subject: Re: [AMPS] Parasitic suppressors/another question,
>
>
>
>
>>
>>>>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.
>>
>>Ah contrair! You yourself have said that the anode-resonant circuit is
>>composed of Ctune. Is not Ctune in the tank circuit???
>>Sooooooo.......tuning the tank circuit DOES make a difference.
>>
>? Adjusting C-tune makes little difference in the anode resonance since
>C-tune is effectively in series with C-anode, which is much smaller.
>
>[Richard W. Ehrhorn] <<< A sweeping generalization which is not
>necessarily true. In many cases - such as big tetrodes tuned by vacuum
>variables - Tune Cmin may be considerably smaller than tube Cout... right?
>
? Surely. The 8973 has 160pF of C-anode. At 29.5MHz, C-tune would
probably be around 100pF. However, in a SB-220 the measured anode
resonant freq. changes little between 80m and 10m operation.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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