Thierry,
First, there is some confusion as to what a G5RV is. Some people refer to
any dipole fed with open wire line as a G5RV. As far as I can determine, a
G5RV is 3/2 wavelength long on 20 meters, fed with 1/2 wavelength at 20
meters of 450 ohm line.
I ran EZNEC on such an antenna, and got SWRs below 3:1 on 20 and 80 meters.
If you juggle things, you can get it below 2:1 on 20. Free space gain was
about 1 dbi on 20, and 2 dbi on 80. On 160m, the free space gain was about
2dbi, but that is almost meaningless because the impedance was 1 - j600.
So, even if your antenna tuner lets you get an SWR of 1:1 on 160, you are
really loading the transmitter into the losses of the transmission line, and
not the antenna. Note that just the DC resistance of 100 feet of #14 wire
approaches 1 Ohm.
Tam/WB2TT
"Thierry" Thierry, see http://www.astrosurf.com/lombry/ wrote in message
...
Hi,
Thanks for all answers.
Ok for the capacitance and other loads than destroy the ability of the 31m
G5RV to work on 160m.
But I must say that on 160m, my TS-570D automatic tuner does a good job. I
do not remember the value but I think that I get a SWR 1:1
I can reach the end the S-meter scale in emission, but at first sight
nobody
hear me, although on 80m I arrived 59++ in near countries.
(if I had observed a high SWR value on my S-meter- say over SWR 3:1 or so,
in all cases I know by experience that I could not emit the slightest
signal
or it should have been very weak).
But I wonder that having a SWR 1:1, nothing looks wrong (not heat, etc at
first sight), but the result is 0.0 on that band !!
PS. As for the one like G4FGQ saying that a multiband G5RV is not a good
antenna or the others saying that it can only work on 20m, I have to deny
these opinions.
I confirmed over 250 DXCC in one year at less than 100 W PEP from 80 to
10m,
including WARC. It works ! Not as a beam of course. But very well for what
it cost (about 100 euros). That stays an excellent investissment, not
necessary if you are hunting DX or want to participate in all contests
(that
stays a dipole than I work barefoot) but for ragchewing in local QSO
(inside
a radius of to say 5000 km) it is perfect. Now if you are a DX hunter or
want to reach all pileups with ease, you can add it an amplifier (as I
listen most far DX at least 53 or so) or purchase a performing "DX"
antenna,
I mean a 5-7 ele beam to place 10m high in an open field.
73
Thierry
ON4SKY, LX3SKY
http://www.astrosurf.com/lombry