This is from the ARRL antenna book:
------------------------------------------------
Practical Suggestions For Vertical Ground Systems
At least 16 radials should be used if at all possible.
Experimental measurements and calculations show that with
this number, the loss resistance decreases the antenna efficiency
by 30% to 50% for a 0.25 wavelength vertical, depending on
soil characteristics. In general, a large number of radials (even
though some or all of them must be short) is preferable to a
few long radials for a vertical antenna mounted on the ground.
The conductor size is relatively unimportant as mentioned
before: #12 to #22 copper wire is suitable.
a.. If you install only 16 radials they
need not be very long - 0.1 lambda is sufficient.
b.. If you have the wire, the space and the patience to lay
down 120 radials (optimal configuration), they should
be 0.4 lambda long. This radial system will gain about 3 dB
over the 16-radial case.
c.. If you install 36 radials that are 0.15 lambda long, you will
lose 1.5 dB compared to optimal configuration.
---------------------
73 -- Larry -- W1DYJ
-----Original Message-----
From: jcjacobsen@q.com
Sent: Wednesday, November 30, 2016 21:02
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Radial Lengths
Gary K9RX had a question about radial lengths and confusion from reading
ON4UN Low Band book. If it helps any, I was always of the belief that there
is a point of diminishing returns. It's better to have more short radials
than only a few long ones. If I remember correctly, the ARRL antenna book
has charts on number of radials for a given amount of wire so as to use said
wire most effectively. It is from an article in June 1985 QST, pgs 28-30 by
N2MF, Brian Edwards. I settled on 32 radials, approx 32' long around a 42'
HB vertical for 160/75/40 meters. Antenna works very well. Into Europe and
Central/South America on all 3 bands. I never run more than 500 watts. On
160 that would equal abt 125 wts ERP, and on 75 abt 250 wts ERP. On 160 I
only miss Hawaii, Alaska, and South Dakota (right next door, darn) for WAS.
I can usually get 40++ states during the CQ 160 SSB the end of February,
even barefoot.
In short (no pun intended) put down as many radials as you can, in the space
you have. BUT I don't think you need to get to anal about it. After all, it
IS AMATEUR RADIO we are playing with. Don't beat yourself up over it. Read
the QST article or look in the handbook and then go at it.
Good luck with your project. 73 K9WN Jake
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