To: | [email protected] |
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Subject: | Re: LF: Capacitive top hat question |
From: | Andy Talbot <[email protected]> |
Date: | Wed, 4 Nov 2015 21:11:09 +0000 |
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16 US units of length ~ 4.9m, so that means it's a bit more than half the height of mine. The top hat is near-enough infinite to all intents and purposes, so its real height is 4.9m.
My antenna is only 7m high, with much smaller top hat. That amount of top capacitance will drastically reduce the ground resistance, so all more than likely all quite an efficient vertical radiator. If there is enough buried metal in the ground it could be very good indeed. so we're probably talking about a similar performance - perhaps an efficiency of -40dB on 137kHz. That's what mines comes out as, anyway. Horizontal radiaitors don't when they are close to a reflector. And the same good ground system that makes it radiate vertically stops the horizontal bit doing anything. If the ground were very poor, sand for instance with littel wire underneath, then perhaps the horizontal part may generate some ExH, but then efficiency would no doubt be so poor that teh Hpol contribution would be insignificant. Not sure why you talk about wire separation, he said they are strapped so its just a two wire, fat vertical. Which is exactly what I use - two paralleled conductors of a twin feed. Vertical antennas really are quite straightforward to analyse / measure Andy G4JNT On 4 November 2015 at 20:21, Graham <[email protected]> wrote:
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