Interesting that a resonant antenna is claimed to radiate better than a
multiband antenna with an antenna tuner at the feed point of the antenna.
Clearly, if coax carries current at a high SWR, the loss will be
considerable, but if open wire feed line is tuned by a tuner fed with coax,
the loss should be no greater than an antenna fed with a base loading coil
or capacitance. An L network tuner has always worked well for me, but I
have never believed in loading coax. A major distraction with resonant
antennas, is low band width. Really compromises the use of the radio.
In practice multiband antennas such as a G5RV or Carolina Windom, exhibit
gain at various frequencies and if properly installed, provide for great
multiband coverage. I feed a 204' dipole at 40' with 66' of 470 ohm ladder
line, tuned with an SG-230 autotuner which is fed with a run of 350 feet of
RG-213 coax buried in underground conduit. This antenna has been an
outstanding NVIS antenna at frequencies below 10 MHz, and works very well up
through 12 meters. This antenna exhibits a 4 to 1 SWR or better without
tuning in almost all amateur bands I use, so it is not a problem for the
SG-230 to match it up (even though this is not a balanced tuner). The tuner
is grounded with a radial system consisting of the coax, one side of the
ladder line feed line, the power ground, and one 6 gauge copper radial
140'long, buried in the ground.
As a point of reference, I have a resonant dipole at 25' high, fed with 40'
of RG-8X coax on 5.330. This antenna does not receive as well as the G5RV
on this frequency, 350 feet away.
This multiband antenna is large and that is a drawback, but it is not as
large as a resonant 160 meter loop. It also receives AM broadcast stations
very well and even the 2nd harmonic of the stronger ones, so it is to much
interference for some receivers and I need to add a High Q preselector when
listening to frequencies that might be interfered with by these strong
stations. The resonant antenna would probably not be receiving these
signals as well and that would make them desirable from that aspect.
Everything is a compromise of something else. Nothing in antenna use is
perfect, that I have found.
Ron KA7U
tractor driver, CW operator, ditch digger and general labor.
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Bruce Lanning
Sent: Thursday, January 19, 2006 8:35 AM
To: TenTec@contesting.com
Subject: [TenTec] Rog K9RB Antenna Tuners
Thoroughly enjoyed your recent article on antennas and antenna tuners. You
are right on the mark. I have been a licensed ham since 1949 an have never
used an antenna tuner. Nothing but losses. Have always used resonant
antennas with coax. Thanks for the very fine disertation.
Bruce W1GBS
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