Topband: Shunt fed tower

[Wayne Rogers]

Herb:  What do you mean "sweet point?"  This has always been a mystery to 
me.  I have a 90' tower with a TH-& etc on top that I am getting ready to 
feed.  I have heard "feed it at the top (just under the beam)" and I have 
heard 55' up.  How does one go about finding the right spot to attach gamma 
rod to the tower?  I plan on using 1/2" hardline outer conductor for the 
line.

Thanks to all for the good advice on this reflector and 73, Wayne N1WR

--------------------------------------------------
From: "Herb Schoenbohm" <herbs at surfvi.com>
Sent: Saturday, April 24, 2010 6:20 AM
To: "w8uvz" <w8uvz at voyager.net>
Cc: "Phil LaMarche" <plamarc1 at verizon.net>; "Topband" 
<topband at contesting.com>; "Kyle N4NSS" <n4nss at yahoo.com>
Subject: Re: Topband: Shunt fed tower

> w8uvz wrote:
>> Hi Phil
>>
>> There is an excellent article in Ham Radio May 1975 by John True, W4OQ on
>> "shunt-feed systems for grounded vertical radiators".  His system uses an
>> omega match for matching the gamma rod (or wires) to the radiator.
>>
>> Using large diameter tubing or multiple wires for the gamma will result 
>> in
>> more usable bandwidth on top band.
>>
>>
>>
>
> Using the other solid aluminum shield on discarded 3/4 inch CATV cable
> end runs (called by some 750 or .750) spaced 24 to 36 inches from a
> towers is a significant improvement over a single #8 wire.  Yet a
> skeleton cage around the tower and taped at or near the "sweet point" of
> 3 or 4 wires is even better.
>
>
> Herb Schoenbohm, KV4FZ
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK