On 7/9/2013 9:45 AM, Richards wrote:
Really? Please explain.
I ask because Rick DJ0IP and I have both spent considerable time
researching and building various OCF dipoles to build multiple-band
antennas which do not depend (or which depend less) on a tuner or
matchbox than other designs (e.g., a G5RV).
Most people don't even know what a G5RV is. It is NOT a multiband
antenna, it was a 20 meter(ish) dipole fed with coax. The dimensions
were not chosen by some radio magic, the length of the top section was
the size of Vareny's garden.
The wire line feeder is not actually a feeder, it's a matching stub
whose length was chosen so that at the radio end of it, it presented a
50 ohm impedance so that the radio could be fed with unbalanced coax.
The fact that it does appear resonant on other bands, or at least can be
matched using a tuner was an accident. Some people are happy about it,
some that think it is working when it is not are not so happy.
It really is proof that no matter what its length is a dipole is a
useable antenna, at any frequency, and the longer it is the better. The
transmatch (tuner) is there to keep your radio from blowing up when you
transmit, it does not affect in any way the resonance of the antenna, or
its performance, although I have heard many hams say that it does. :-(
BTW, there are many G5RV "type" antennas on the market that bear little
or no relation to the original antenna. It has become a generic term for
a dipole with an open wire feeder matching section, and in some cases,
an open wire fed dipole. :-(
73.
Geoff.
--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
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