[Mobile-Portable] Iron Horse 40m Ground?

[D C Macdonald]

The biggest plus for the "longer" whip (or capacity hat)
is that it reduces the size of the lossy loading/resonating
coil that is required to attain resonance on a loaded whip.

I believe that there must be  SOME  radiation from the top
whip, as shown in all the handbook current distribution
patterns.  Admittedly, that radiation will be minimal, but
it will exist and contribute to the overall efficiency.  I use
a High Sierra 1500, but use a 7 foot whip instead of the
prescribed 68" whip.  This enables less of the coil to be
engaged and  WILL  add to the overall efficiency of the
the  ANTENNA SYSTEM.

I know that the efficiency of this type of mobile antenna
is less than that of the "bugcatcher" antenna, especially
on 40 and 75.  It is a compromise I am willing to accept
for the convenience of not having to stop my truck to
change bands/frequencies.  My experience has been such
to indicate that a good "screwdriver" type antenna is not
more than a dB or two under the average bugcatcher on
40 or even 75.  One of the "monster" bugcatchers is likely
to have an advantage of 3-5 dB, but one of those is not
likely to be "wife-approved" even if that wife is a ham, as
mine is.

73  ---  Mac, K2GKK/5



----Original Message Follows----
From: w3dya at juno.com
Reply-To: Mobile-Portable Reflector <mobile-portable at mailman.qth.net>
To: mobile-portable at mailman.qth.net
Subject: Re: [Mobile-Portable] Iron Horse 40m Ground?
Date: Mon, 19 Jul 2004 16:00:40 -0500

Reading Tom's note was interesting.

Does anyone really believe any part of the mobile antenna (mast,
resonator, stinger) radiates RF except the mast?  I'm referring to the
top-loaded arrangement I've been using for many years:  54" Hustler mast
mounted on the rear bumper with several resonators mounted on the mast in
almost vertical position.

Recently I added 18" to the mast and mounted my resonators horizontally,
which gives me more radiation area with the 6-foot mast.

Remember, the mast radiates, not the top-mounted coil except maybe for
the first couple of turns... and certainly not the stinger (or the spring
above the resonator coil).

I know this because county hunters have the good luck to have an antenna
expert (no exaggeration) in our group.  So I would like to see comments
on this reflector more accurately reflect what actually happens with
mobile antennas.  For example, lengthening the mast to get the resonator
higher above the cab of a pickup is good... but only because it extends
the mast above the cab.  Of course, current (and radiation) is highest at
the bottom of the mast and diminishes as it approaches the coil.

Don't look to me for any technical help or advice about antennas or
anything else electronic.  I just remember what I've been told by someone
who does know based on test results - and my mobile antenna reflects his
advise and has been very successful for me.

I promise not to disrupt your technical exchanges with BS; just wanted to
see if we have a basis for mobile antenna advice.

73, Norm, W3DYA
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