It was the first idea that crossed my mind too, but when I did some basic
calculations on it based on the figure from Marco (up to 5dB flucuations in
antennacurrent) you must be willing to 'heat' up to 90% of the power in the
'bleeder resistor' to reduce the flucuation to 1dB. In practice this would
mean that you would need about 100-200 Watts RF power to radiate 10mW at
+/-1dB.
With some feedback from the antenna current to the TX (may sound
complicated but is just some kind of ALC) you only need a 10-20 Watt TX.
I think that using an additional resistor is a good solution for some short
tests, but for longer use a small TX with antenna current regulation could
be preffered.
73, Rik ON7YD
At 17:33 3/05/00 +0000, you wrote:
From: "LAWRENCE MAYHEAD" <[email protected]>
To: "rsgb lf group" <[email protected]>
Subject: LF: Re. Beacon Power control.
Date sent: Wed, 3 May 2000 16:37:07 +0100
Send reply to: [email protected]
Hi All,
Perhaps this is just too naive-but would it not be possible to put a
resistor in series to swamp the Ant.system resistance so that changes in
it have little or at least less effect on the current! This would of
course require more power to get the required current but for such a low
power beacon this should not be too difficult. 73s Laurie.
Plus it would buffer the TX against changes in load - or, looked at
another way, it would reduce the Q of the antenna so tuning would
be less critical. Sounds like a great idea.
Cheers, Jim Moritz
73 de M0BMU
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