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• To: tesla-at-grendel.objinc-dot-com
• From: sroys-at-Anchorage.ab.umd.edu
• Date: Mon, 25 Apr 1994 14:57:15 -0400
• >Received: from anchorage.ab.umd.edu by csn-dot-org with SMTP id AA03796 (5.65c/IDA-1.4.4 for <tesla-at-grendel.objinc-dot-com>); Mon, 25 Apr 1994 12:58:50 -0600

There were a couple of questions about RF chokes.  They are used between the
HV primary supply and the primary resonant circuit to keep the high voltage,
high frequency currents from getting back to your transformer and frying the
insulation.  The design isn't critical since I don't think it alters the 
primary tuning or any other circuit parameter (with the possible exception 
of transformer loading...has anybody investigated impedence matching with 
the primary transformer?).  To use the RF chokes, they would simply connect 
the primary transformer HV output (one per terminal) to the rest of the 
primary circuit.  The three main schools of thought on the matter of RF chokes 
I've heard of are:

    1. Use 10-20 turns of wire around a 1"-3" air core form (low inductance).
    2. Use 3 to 4 layers of wire wound around a steel core (high inductance).
    3. Don't use 'em, they're esentially useless on low powered systems.

I use option #1, but then I've burnt up a couple of neon sign transformers 
in my time so I might not be the most credible source.  I've wondered about 
high inductance chokes, but I haven't gotten around to trying anything out.  
Any knowledgeable comments about the relative merits of the differrent chokes 
would be most welcome.

                           Steve.

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