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Von: Mike Dennison[SMTP:[email protected]]
Antwort an: [email protected]
Gesendet: Freitag, 23. Juli 1999 10:29
An: [email protected]
Betreff: Re: LF: 22. july
DL1SAN wrote:
>
> Yesterday I installed abt. 20 radials (10-35m) to my antenna system. But
> there was no significant change of the antenna current. The current is
abt
> .6 A with and without the redials. Can anyone explain this?
>
It is possible you have altered the impedance of your system and
need to re-match it to the Tx.
The radials did not change the tuning significantly.
For a better understanding i try to describe my antenna and tuning
circuit.
Form the wall feedthroug a 8m long wire ( 2 in parallel 30 cm apart)
is fed to a mounting point of the chimney which is abt 9 m over ground.
There an inductor with abt 1mH is installed. From the inductor three wires
abt 10m long are tensed in 3 different directions. the ant is tuned with a
fixed inductor, abt 2 mH, and a variometer for fine tuning. For exact tuning
the antenna current and voltage is measured. Also the phase angle of current
and voltage is monitored to find the "real" tuning point. With the same tool
foreward-, back power and the phase can be measured. Former I did these
measurements with an oscilloscope and a current coupler . Last month i built
a power-amp,volt meter with phase measurement capability. This is smaller
than a oscilloscope and more useful for portable operation.
I hope this will answer a few open questions.
73 de Wolf (DL1SAN)
Mike, G3XDV (IO91VT)
http://www.dennison.demon.co.uk/activity.htm
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