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Rik, Stefan, I follow your points but there would
seem to be something strange in Rik's antenna or his appreciation of what/how
its working.
Contrary to an earlier assertion, the antenna
current flowing through Rrad generates the radiated power, so lower current, if
Rrad doesnt change, MUST mean lower tranmitted power. It matters not that
the SWR is unity. A unity SWR indication at the transmitter says that the
impedance at the end of the coax is 50ohms, but it does not necessarily indicate
the the the antenna is resonant i.e the inherent capacitance of a short antenna
totally compensated by the loading inductance. If we assume that Rrad+Rloss does
not change across the band the matching transformer should transform the value
of Rrad+Rloss to 50 ohms across all the band. The coax will now be matched and
will present 50ohms at the shack end. If this does not happen I would be
inclined to suspect currents induced in the coax braid. SWR indicators can
easily be confused by induced braid currents......could this be the cause of
Riks strange effects? This might be a function of having a "better" ground in
the shack than at the base of the antenna.
Alan
G3NYK
----- Original Message -----
Sent: Friday, November 08, 2013 6:53
PM
Subject: Re: LF: remote antenna
tuning
Oh yes, or, a phase meter (M0BMU) and a battery operated
variometer motor. Without an additional cable to the shack. Then the SWR meter
in the shack confirms that everything is fine.
73, Stefan
Am
08.11.2013 19:40, schrieb pat:
Hi All,
A suggestion: battery operated
tuning device at antenna end and "wireless" link back to shack. Wireless can
operate at a non-interfering frequncy
(HF/VHF/UHF/Optical).
73
On 08/11/13
16:09, Stefan Schäfer wrote:
Hi
Rik,
Am 08.11.2013 16:06, schrieb Rik Strobbe:
Hi Stefan,
remote tuning of
the loading should be done by optimizing SWR
(at the TX), not for maximum RF current.
If one keeps that in mind there is no
problem. ...which is in agreement with what i
said.
But once you have matched your antenna to 50 Ohm on resonance and
you can only vary the reactive part of the antennas impedance (after doing
QSY), then you will get the maximum antenna current at best SWR (assuming
that Rrad+Rloss is constant which is not to far from reality).
I am not sure if I will keep
the remote variometer tuning. It needs some
extra wires to the loading coil and
I am not sure how long the small DC
motor will function properly with all the rain
and frost coming up. Here it holds since more
than 2 years for LF now..
73, Stefan
--
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK
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