[Antennas] Mobile Antennas - which shoots best, is strongest?

[David J. Ring, Jr.]

Hi Jack,

I agree with you completely.  My question was just has Doc noticed a big 2 
or 3 S-unit difference which I believe was caused by using a ATU (the same 
Harris unit he is using - the the vacuum variables) at the whip feed point 
and (as I did) using the same type whip fed directly with coax but with 
about 30 feet of mismatched coax and then terminating on a small MFJ tuner 
sitting on top of my radio.  Same radio, same antenna - the difference was 
two different coax runs (unlikely but possible) and the two different ATUs - 
one the Harris at the antenna feed point  - and the other the "cheap" MFJ at 
the radio end of the feedline.

I love verticals for long range - they are great.  They're also great for 
skywave (think broadcast AM and marine 500 kHz CW) but low horizontals are 
great for NVIS propagation.

But if I want to do NVIS range, I use a telephone!

I think working Japan on 80 meter SSB from New England is exhilerating.

73
David N1EA
----- Original Message ----- 
From: "Jack Painter" <223bthp at cox.net>
To: <Antennas at mailman.qth.net>
Sent: Friday, June 16, 2006 2:28 AM
Subject: RE: [Antennas] Mobile Antennas - which shoots best, is strongest?


Hi David,

The problem with any whip including of marine design mounted on or alongside
a house is the lack of ground plane. As Doc put it so well, the need for a
counterpoise is almost as important as any antenna choice, as they all
require it. This in spite of various design promises.

Besides omitting radials (the #1 mistake from most accounts), another common
problem when trying to residential-mount a marine whip is failing to place
the coupler/ATU right at the feedpoint of the antenna.

Using identical equipment, a small vessel with the whip mounted anywhere
generally does poorer than a large vessel with the whip mounted anywhere. I
have never seen comparisons of how the shipboard mounting location affects
the efficiency and radiation patterns, but we all have examples of the small
(motor) vessel getting poor-mediocre performance no matter how it was
mounted. People then try to mount that same marine antenna on a "small
house" (relatively speaking), use no radials, mount the ATU wherever
convenient, and then wonder why the thing won't work on 160 meters!

Cheers,

Jack