SV: [AMPS] Nichrome/Parasitics/ARRL Handbook 2000

[Ian White, G3SEK]

Jon Ogden wrote:
>> The quick answer is no. It will move the VHF resonance, but a simple
>> inductor does nothing to add extra damping at that frequency compared to
>> HF. To do that, there has to be some loss mechanism in there too - a
>> resistor and/or a lossy conductor.
>
>Ian,
>
>I don't disagree with you, but an inductor of significant size can affect
>the resonance enough to move it out of an area where the tube will not want
>to parasitically oscillate.
>
Fair point - my original comment was too sweeping. 

>I know this for a fact cause my 4-1000A has NO resistive suppressors in the
>anode and it is stable and has been stable under all sorts of loads and
>conditions for a year now.  With a traditional suppressor network, one could
>easily find a resonance at the typical 4-1K frequency of 80 MHz or so.
>However, with my inductor on the output of the tube, the resonance at 80 MHz
>is no longer there.  It has moved somewhere, but I've not been able to find
>it anywhere in the range of 30 MHz to 120 MHz. 

Surely there always has to be a second resonance, somewhere above the
operating frequency. Since the series inductance in the anode lead tunes
it, it presumably moved lower in frequency. 

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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