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Hot Antennas

To: <>
Subject: Hot Antennas
From: (Rob Hummel)
Date: Wed, 3 Jul 1996 09:05:28 -0400 (EDT)
>Well, I have some problems with the premise that the KT34XA traps have that
>much internal resistance that there is significant heating under rf load...

It's really not that hard to understand. Let's boil down the math for a
simple loss budget for a connection made with a ham-type UHF connector.

Loss per connector = 0.05 dB (doesn't seem like much, eh?)

Total loss = 0.10 dB (who even counts this stuff, right?)

1500 W * 0.10 dB =
1500 W * (1 - 10 ^ (.01)) =
1500 W * .0233 =
                                35 Watts!

That's right. For every connector pair, you lose 35 watts.

A 0.3 dB loss in a switch subtracts 107 watts from your ability to break a

And for every 1 dB of loss in your feedline you squander 388 watts.
(So much for the guys who say, "Oh, RG-8 is essentially lossless at HF.")

Assuming that the connections to a typical trap combined with ohmic
resistance has the same miniscule 0.1 dB loss as a connector pair, it's
essentially a 35W heating element. No need to climb the tower. Just turn a
35W bulb on for a while, then grab it tight to simulate this experience in
the comfort of your living room!

For a safer thrill, add up a loss budget for your station and see how little
of your power is actually reaching those expensive antennas.
 Rob Hummel (WS1A) <>

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