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Message-ID: <3.0.1.16.20000503190040.232f556e@mail.cc.kuleuven.ac.be>
Date: Wed, 03 May 2000 19:00:40
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: Re. Beacon Power control.
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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" <LAURIE@g3aqc.freeserve.co.uk>
>To:             	"rsgb lf group" <rsgb_lf_group@blacksheep.org>
>Subject:        	LF: Re. Beacon Power control. 
>Date sent:      	Wed, 3 May 2000 16:37:07 +0100
>Send reply to:  	rsgb_lf_group@blacksheep.org
>
>> 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
>
>
>
>