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[TowerTalk] 2nd Radio 10-15-20m Antenna

To: <>
Subject: [TowerTalk] 2nd Radio 10-15-20m Antenna
From: (Eric Gustafson Courtesy Account)
Date: Sun, 21 Jun 1998 12:50:33 -0700

To: <>
>Date: Fri, 19 Jun 1998 21:12:44 -0500
>From: W9SN <>
>Dale L. Martin wrote:
>> Today, I arrived home about 6:00pm to find the Hy-Gain 12AVQ I
>> ordered last week sitting on the front porch.
>> After changing clothes, reading the mail, opening the box,
>> checking parts (all there, plus a couple of washers), collecting
>> tools, and start assembling the antenna, it's 7:00pm.
>> By 7:30pm, I've mounted the antenna, sunk a ground rod, attached
>> said ground rod to the antenna, and am sitting in the grass in
>> the backyard checking SWR with my MFJ-259.
>> A bit high on each band...about 1.5-1.6:1.  Get the step ladder
>> and make a two adjustments.
>> Scrounge around a bit for enough coax pieces to reach the garage
>> antenna patch panel.
>> At 7:40pm, I'm sitting in my radio room at the Omni VI+ checking
>> SWR on the three bands.  1.3:1 or less across the CW portion of
>> each band.  1.8:1 or less across the three ham bands (CW and
>> SSB).
>> Now, should I put out radials?
>> Dale Martin, KG5U

Then Steve Narducci <> wrote:

>Well that depends if you want to lower your take-off angle of

While an extensive and dense ground screen can indeed lower your
takeoff angle, we should be sure that this much screen is what we
are talking about before discussing TOA improvement.

>Right now without any radials, your signal is going nearly
>straight up.

No, it isn't.  The pattern towards the zenith will be nearly
zero.  Over average ground the TOA will be in the 25 to 30 degree

>This is good for local qso's but if your after the dx, then by
>all means put as many as you can out there.

This is good advice for either case.  It is good because it will
no doubt raise your system efficiency.  Better to use your TX
energy for communication than for worm warming.

>Swr is not an indicator of the performance of that vertical.  On
>the contrary, the more radials you put out, the narrower your
>bandwidth will become and you will see steeper skirts on the swr

True.  Lowering the system losses for this structre will improve
the "Q".  Very probably, the SWR curve will become a bit steeper
as a result.

>I always like to see that (narrower SWR curve) cause I know I
>have done some good in lowering my take off angle.

I assume we are talking about 1/4 wavelength radials here.  TOA
is not at all affected for a 1/4 (approximately +/- trap loading
effects) ground mounted base fed vertical radiator until the
ground screen radius is in the 1/2 wavelength and longer range.
To bring the TOA down to say 5 degrees requires a screen radius
of about 3 wavelengths.

This is not to say that the shorter radials are useless or
unnecessary.  They can and probably will make a great improvement
in the overall system efficiency.  And are therefore well worth
doing.  Just don't expect significant TOA improvement unless you
are willing to contemplate a really extensive screen.

73, Eric  N7CL

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