[Amps] Plate Choke Resonances

[Robert Groh]

Thanks, Bill - actually you have explained what folks here mean when they talk about 'Tesla Effect' - now I have something to get my neuron's around.  We are talking about the rf levels when we 'grossly' mistune a PA, e.g. tune the PA for a 50 ohm load and then disconnect the load.  Or, alternatively, swing the plate impedance all over the Smith chart while watching out for excessive power/voltage/current in any of the components - the biggie for most of us being the RF choke. 

The usual meaning (or what I get is the usual meaning from looking at other sources on the web) for the Tesla effect is coupling from one element to another via magnetic and/or capacitive effects.  The meaning here is more to do with off-resonance effects. 

Bob




________________________________
From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
To: Amps reflector <amps at contesting.com>
Sent: Sun, January 31, 2010 7:12:09 PM
Subject: Re: [Amps] Plate Choke Resonances

ORIGINAL MESSAGE:

On Sun, 31 Jan 2010 09:33:56 -0700, Larry Benko <xxw0qe at comcast.net>
wrote:

>This forum should be about increasing knowledge rather than telling 
>people how they just never experienced some magical event that is too 
>complicated to simulate.

REPLY:

Well if the Tesla effect is too complicated for you to simulate, how
about doing it in real life?

1. Tune up your amp at full power into an antenna or dummy load.
Measure the peak RF at the tube anode or input to the tank circuit.
The peak RF should be approximately equal to the value of the DC anode
voltage.

2. Unplug the antenna and keep the drive the same. Measure the peak RF
again. Hopefully it won't destroy your meter or burn up something in
your amp.

You have just observed the Tesla effect - a peak voltage that is far
higher than the DC input would normally produce. It is caused when a
parallel resonant tank circuit which is lightly loaded accumulates
very large amounts of energy due to the so-called "flywheel effect".
This condition is common during the tune-up of an amplifier, before
you reach the final fully loaded condition. This is when the RF choke,
if parallel resonant, is most likely to smoke. 

4. I am sorry your software can not simulate this. Perhaps there is an
upgrade available?  :-)

73, Bill W6WRT
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