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Re: Topband: RG11 75ohm and 4 square 80m

To: "'Stein Roar Brobakken'" <s-roabr@online.no>, "'Topband Reflector'" <topband@contesting.com>
Subject: Re: Topband: RG11 75ohm and 4 square 80m
From: "Tom McAlee" <tom@klient.com>
Date: Wed, 22 Apr 2009 17:53:43 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
> So does the 4 Square accept if I use ½ wl of 75 ohm to each vertical ?

Not for the Comtek ACB-4.  Use coax with a VF of 0.8 to make sure it will
reach (such as Belden 8213) or use 3/4 wl instead.

> Can anyone tell me How wide is a 80m 4 square in frequency ?

It will depend on the diameter of the conductor.  Wire verticals will have a
narrower bandwidth (most likely not covering the entire 80m band under 2:1).
I use verticals that taper from 2.125" to 1.25" and they cover it under
1.5:1.  Verticals made of 25G will have no problem.

It also depends on the efficiency of the radial system, especially for short
verticals.  A short vertical with a lousy radial field will have a great SWR
bandwidth but that doesn't mean the antenna is radiating well.

I'm not sure about using a MFJ-259B to measure the lengths.  However, a time
domain reflectometer (TDR) would give good results.

73
Tom NI1N


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