Jake, K9WN wrote:
----- Original Message -----
To: "Charles Bibb" <email@example.com>; "Topband"
Sent: Sunday, August 26, 2007 7:29 PM
Subject: Re: Topband: Top band Resonat freq of 90' tower
> Charles, K5ZK, was wondering about the res. freq of his tower, 90' with
> KT34XA. After giving him a wise guy and SWAG reply, my curiosity was
> tickled, so I booted up EZNEC.
> Charles, I used a 90' tower, 12" in diam, with a 32'/3" boom at the top.
> ELNEC says resonant freq is 2.15 mhz. Bandwith is about 200 khz +/-.
> This might give you a starting point. FWIW, the 90' tower alone is
> resonant at about 2.6 mhz with abt 350 khz BW.........
> Again, good luck with the project.
> K9WN Jake
I believe the coupling of the feed line to the driven elements of the
KT-34XA probably lowers the resonant frequency by adding a little top
loading. I cannot prove it and Jake is correct that the 32 ft boom top
loads the tower down to 2.15 MHz.
Connecting the center of the 3rd director and the center of the reflector to
the antenna boom provides a lot more top loading bringing the tower and beam
configuration to about the bottom end of 160.
73, George K8GG
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