On Thu,8/4/2016 9:16 AM, Ignacy wrote:
> With 43 ft vertical a tuner at the base is critical to performance
It is FAR more complicated than that. Antenna tuners provide a match
between a transmitter and a feedline, or between an antenna and a
feedline. Like antennas like the G5RV, a 43 ft vertical is WILDLY
mismatched to 50 ohms on most bands, which makes serious matching at the
base important. HOWEVER -- it has been shown that if the feedline is of
high quality, like 1-2-in hard line; and 2) if it is fairly short (less
than about 50 ft); and 3) some matching is done at the feedpoint, a
tuner in the shack can match the antenna to the transmitter and feedline
loss will be sufficiently low that it's not an issue.
I've studied the 43-ft vertical, and reported on what I've learned in
this set of Power Point slides for a talk I did several years ago at
Pacificon.
http://k9yc.com/43FtVertical.pdf> and KAT3 may in some cases be detrimental.
I cannot imagine the logic behind this statement.
> Check the signal reports with both antennas. At my QTH verticals nearly
> always are 10db down from dipoles even for DX, except when dipoles have
> nulls.
The relative performance of horizontal and vertical antennas is STRONGLY
dependent on 1) soil conditions; 2) their height; and 3) for verticals,
their counterpoise/radial system if they need one. An HF vertical
mounted at roof level will outperform the same antenna mounted at ground
level, and the degree of outperformance will depend on soil conditions.
Some verticals are fundamentally dipoles, and do not need radial
systems, so they are easy to put on a roof. The R8 and AV640 are
examples. Other verticals that are designed as quarter wave antennas
with loading coils DO require radials, so if you put them on a roof, you
need at least one for each band where plan to transmit, and two per band
is better.
> In this case your better option is adding an extra G5RV
> perpendicular to the first G5RV, also fed by flat line.
I'm not at all a fan of antennas like the G5RV, primarily because they
cannot be choked to kill RX noise. Adding another one would be a bad
move. Far better are antennas like resonant fan dipoles fed with coax,
and yes, if you can, place two at right angles. Resonant, coax-fed
antennas CAN be effectively choked, so RX noise can be lower. You can't
work what you can't hear!
73, Jim K9YC
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