[TowerTalk] Relay Ratings Question

[Bill Turner]

ORIGINAL MESSAGE:

On Thu, 23 Aug 2007 12:20:29 -400, trife at sirus.com wrote:

>Am I missing anything in this analysis?

------------ REPLY FOLLOWS ------------

You can't use ohm's law directly with this circuit because of the
reflected wave from the upper part of the antenna. You will find the
voltage at the top, or near the top, of the coil is far higher than
ohm's law would predict. The shorter the upper part of the antenna,
the higher the voltage.

I would connect up everything without the relay and install a
temporary, adjustable spark gap where the relay will go. You can make
it out of a pair of wires with sharpened ends. Adjust them back and
forth to estimate the voltage present. Use the figure of 30 kV per
inch to calculate the voltage and add a reasonable safety factor for
the relay. 

Bill W6WRT