Hi Jeff,
Tnx for the info.
Using 10% of the power hitting the dump post with 1/4 wave elevated RG6 with
100 beads at each feedpoint I get about 150 KHZ on 80M and 200 KHZ on 75M
bandwidth. If I used buried RG6 and using your 3X figure maybe I would only
have about 50KHZ on CW and 75 KHZ on SSB.
I would gain more choking with the 3/4 wave feedlines. But would the
difference be noticeable?
By the way, the spacing of the feedpoints, the length of the feedlines and
the verticals are based on 3.65 MHZ.
The 41' elevated radials at each feedpoint are tied to a coil to resonate
the antenna at 3.77 MHZ. I add an additional series coil to bring it down to
3.55 MHZ.
73,
N2TK, Tony
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Jeffrey Ach
Sent: Friday, January 27, 2017 9:46 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 4 square for 80
>From my experience, what you give up going to ¾ wave feedlines on an
elevated radio wire 4 sq is quite a bit of bandwidth. I measure bandwidth
as the frequency excursions which result in 25% of the power hitting the
dump port.
My wire 4 sq for 80 (straight up vertical wires to catenaries hung from the
tower) uses 3 elevated radials for each, simple commercial current chokes
that measure pretty good Z at 80 meters. These do not add a lot of
electrical length other than the coax, they are just beads on Teflon coax
inside.
When I first installed this antenna in 1991, I used ¾ wave RG-11 buried in
the ground. The bandwidth (see above) was no more than about 50-60 KHz.
This wasn?t? too much of an issue on CW, but was dreadful on phone. I
changed it to ¼ wave and strung them above ground about 3 years later, and
the bandwidth increased nearly 3x of what it was before.
Jeff ? W2FU
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