Pete, et al.
It really helps if you know the self-resonant frequency of the tower.
ON4UN goes into a fair amount of detail in his Low-Band DXing book. There
are examples and graphs that may or may not fit your exact configuration,
but you will get an idea of what affects tap point, bandwidth, gamma wire
diameter and spacing. If I put it this information together, it seems to be
very close to what I already have installed.
In my case, the tower is 120 ft. however a 24' triibander at 100' ft likely
dominates the top loading. There is a 2 el 40 at 115' but since the
elements are insulated and only the boom is at tower potential, it likely
isn't in play much.
My gamma spacing is about 30 inches, tapped at 70', and the gamma-wire
diameter is just a single #10 wire. However, according to ON4UN, the wider
spacing of the gamma-wire decreases the height of the tap point somewhat.
My VSWR isn't flat, but about 1.25:1, which is close enough. I strongly
expect that if I raised the tap point I could lower it.
I am using a single series "C" for the match.
Jim - KR9U
----- Original Message -----
From: "Pete Smith N4ZR" <n4zr@contesting.com>
To: <topband@contesting.com>
Sent: Wednesday, August 27, 2014 6:28 AM
Subject: Re: Topband: Shunt feeding tower
> Reading about 3-wire cages and the like, I feel a serious case of shunt
> envy. Mine is a single wire about 18 inches from one corner of my Rohn
> 25, connected to the tower at about 50 feet. I used an omega match with a
> couple of 3 KV transmitting variables, because my tower is quite tall for
> 160 (97 feet with 3 yagis, 2 on top) and I could not find a 50-ohm
> point.It was absurdly easy to adjust and seems to work quite well at 100
> watts. I'm sure there are better solutions (including Herb's), but this
> was really simple.
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
> On 8/26/2014 5:12 PM, Don wrote:
>> I would like to get on 160 this question most likely has been asked a
>> 1000 time but I need information as how or can I shunt feed my 55 ft rohn
>> 45 .
>>
>> Don
>>
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