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[TenTec] transmission lines; TT query

To: <tentec@contesting.com>
Subject: [TenTec] transmission lines; TT query
From: rohre@arlut.utexas.edu (rohre)
Date: 23 Sep 1997 16:47:21 -0500
I did shift gears on the group.

I should have made clear that truly balanced transmission lines do not
radiate.  I did not say balanced lines radiate, but that a transmission line
which did (coax would be included), would influence the pattern, and my
definition of lossy would, in that case, be anything that detracts from the
pattern of the antenna itself.  If you notice, I did say it was lossy if the
line was not in the clear, implying it was radiating where you would not want
it to, or could not use its radiation to communicate.

Mainly, the downside, in my opinion, is such a line picking up local noise. 
Consider the lower noise of the Gap antennas where the feedline coax is
sleeved before it reachs the feedpoint.  This provides a measure of noise
reduction over more conventional verticals.  (This is a vertical dipole, with
the coax entering the bottom of one half of the dipole, to reach the dipole
feed point.)

Old time tuned lines Might radiate, if you did not balance the lines by
exactly tuning both sides, and with variations in capacitors and inductors
that was likely a problem.  I notice many of those old diagrams show an RF
ammeter in each leg of the feeds; this must have been their attempt to measure
and maintain balance.  Unfortunately, the RF ammeters even at the time of WW2
would only go to 20 M Hz, and their accuracy was probably only 5%?  I need to
get out a couple I have and compare them, and learn more about that.  Another
example might be the old end fed Zeppelein antenna, where one side went to the
wire flat top, and the other ended at the insulator.  Read Moxon to find out
why that antenna did not work the way the inventors thought it did.

As to resonant antennas being  more efficient, one does not see this discussed
much in the ARRL Handbook; but most texts on Acoustics clearly describe
resonance effects creating more output in Acoustical systems.  The physics
should scale in frequency.  Everyone has heard the Booming of the peak point
of a bass speaker.  I find it interesting that the subject of antennas
efficiency is not completely covered.  Awhile back, Lew McCoy started
discussing it in CQ, but even his piece seemed to come up short and not cover

One of the best antenna accessory items I have found is the kit Ten Tec makes
which is a combined HF/VHF watt meter and SWR bridge.  Its dual  HF power
ranges (20 W and 200 W) have the bonus of being capable of scaling from 20
watts full scale on the low range to 2 watts at the twist of a calibration
pot.   At $49, it is a great buy, and its heavy steel case can be used with
the larger coax cables without being dragged over the operating table.  Its
VHF range of 2M can also be used as a relative indicator on 440, further
expanding its utility.

Has anyone been inside their artificial ground kit?  Is it just a series tuned
circuit like the MFJ?

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