[Lowfer] No luck with - JH

[pbunn at patbunn.com]

John,

I agree that some of the test data is not scalable, but I do not agree that 
radials should be limited to the height of the antenna (especially if it is 
5 feet high) nor do I agree that two radials is half as good as many. If 
that were the case, I'd double my power and forget about it.

I was trying to get the point across to John is that one 8' ground rod and 
4 -  5' rods will not be very effective. He needs some radials and if he 
adds some he will improve his ERP. I certainly was not telling him he needed 
2000 foot length radials - "as long as you can make them" for most people is 
a couple hundred feet.



Pat Bunn
N4LTA



-----Original Message----- 
From: John Andrews
Sent: Saturday, December 01, 2012 9:26 PM
To: Discussion of the Lowfer (US, European, &UK) and MedFer bands
Subject: Re: [Lowfer] No luck with - JH

Pat,

Those articles were excellent. But I don't recall if they were aimed at
5 foot verticals on 160 meters or 2.5 foot versions on 80 meters. That's
the kind of scaling that Garry was talking about. A 50 foot antenna at
actual LF (185 kHz) is going to be very inefficient with any practical
ground system for amateur/experimental use. His point was that you can
only go out just so far on typical house lots or small fields, and the
concept of diminishing returns seems to come into play.

And since most of us have to put up with nearby houses, trees and
shrubs, ground wires are only going to help to a certain extent. I
really don't think that some of this can be modeled well at HF. For
example, "ground" is mostly resistive at 185 kHz, but has significant
dielectric properties at 3 MHz. Some of the older literature really
isn't all that useful - Laporte wrote mostly of large
commercial/government installations, and George Brown did most of his
work just below 80 meters.

John, W1TAG

On 12/1/2012 3:31 PM, pbunn at patbunn.com wrote:
> I would recommend reading the excellent QEX articles on radials  that
> were published over the last few years. They did extensive testing with
> short, long and skewed radials as well as elevated radials.
>
> Pat
> N4LTA
>
> -----Original Message----- From: Garry Hess
> Sent: Saturday, December 01, 2012 8:12 PM
> To: lowfer list
> Subject: Re: [Lowfer] No luck with - JH
>
>> Ground rods are not a substitute for radials. At lf,  they need to be
>> as long as you can make them
> and as many as you can afford.
>
> I beg to disagree. Page 3 of The Lowdown, July 1980 article by Ed
> Phillips (available for download at
> http://www.maxmcarter.com/lwantennas/index.html) cites the following
> conclusions of E.A.Laporte's 1952 study of ground systems:
>
> (1) "... radials of length equal to the antenna height are almost as
> good as those of infinite length, and that a length of half the antenna
> height (outside diameter of radial system equal to antenna height) is
> about 2/3 as effective as very great length."
>
> and
>
> (2) "... 2 radials are about half as good as a very large number, and 16
> radials are within a few percent of being as good as 112.
>
> Thus, one need not fear that thousands of feet of radials are necessary
> to produce a lowfer that can be heard out of the back yard. I'm quite
> happy with the performance of my lowfer vertical antenna of 35' height,
> 15' tophat, and 8 x 35' radials (4 of which are terminated by 4' ground
> rods; a pair of 8' ground rods are located at the antenna base).
>
>
>
>
> No virus found in this incoming message.
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