sm5ki wrote:
>
>The other day I send message to this net that included:
>
>"In order to get a good effiency on 28 MHz why not lower the anode impedance
>by inserting an inductance beetween the anode and filter? I see an example
>in my 1991 ARRL HANDBOOK an example:
>
>A tube with 3500 ohms anode impedance and 10 pF output capacitance is
>transformed into 1481 ohms and 16 pF by inserting a 1 uH inductance beetween
>anode and output filter. Will this inductance act as a parasite choke as
>well?"
>
>I did not get any answer on my very last question from you pi/piL
>specialists.
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.
Sorry, I don't have time to look at this in detail right now, but the
spreadsheet that I would use is on my web site. It includes a function
to find the VHF resonance.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|