Hi Alan,
>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?
That's exactly what happened to a fellow ham on SW.
When he had tuned the vertical antenna at the feedpoint to SWR 1 (ref. to 50
Ohm)
he observed a different SWR in the shack.
I suggested to insert a common mode chocke and the strange effect was gone.
73
Clemens
DL4RAJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Alan Melia
>Sent: Friday, November 08, 2013 8:35 PM
>To: [email protected]
>Subject: Re: LF: remote antenna tuning
>
>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 -----
> From: Stefan Schäfer
><mailto:[email protected]>
> To: [email protected]
> 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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