Except for what I'm about to say, what Jim says in his first sentence is true,
which of course includes his post:-)
The velocity of propagation in a wire, near to, on, or below the ground is
different from the same wire in free space. How different? Most people don't
know, don't care or couldn't determine it if they wanted to. But it has been
shown that for these radials, especially when few in number, efficiency actually
/improves /when their lengths are less than 1/4 lambda. See: "Experimental
Determination of Ground System Performance for HF Verticals...", by Rudy
Severns,* N6LF, QEX, Jan/Feb 2009 pp 48-52.
* I can't recommend highly enough Rudy's work on vertical antennas.
http://rudys.typepad.com/ He writes this stuff faster than I can read it.
Wes N7WS
On 12/29/2016 11:58 AM, Jim Brown wrote:
Nothing in this post is true. Optimum length for a counterpoise is a quarter
wave. Radials are a form of counterpoise, and their optimum length is also a
quarter wave. More radials reduce ground losses. Failing to provide an
adequate counterpoise will cause the antenna's return current to flow on your
coax, which makes the rig hot with RF. That's not much of a problem with 5W,
but it can be a very big deal with 100W or more.
Of course, it does depend on what you mean by "much" and "minimal." Inadequate
counterpoise or radial systems can easily reduce you signal by 6 dB. That's an
S-unit, and it reduces your 5W signal to 1.25W. I wouldn't call that minimal
or "not much."
73, Jim K9YC
On Thu,12/29/2016 7:30 AM, Fred Moore wrote:
With an end fed 1/4 wave you only need a counterpoise that is about .05
wave length. it can be the coax or another counterpoise. Although a
counterpoise has some effect on radiation pattern of a quarter wave
radiator, it is minimal. You won't see much improvement in performance
by going above .05 wave length.. it's not worth the trouble to increase
the counterpoise length..
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