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Message-ID: <3.0.1.16.20000503100301.2e77a8b0@mail.cc.kuleuven.ac.be>
Date: Wed, 03 May 2000 10:03:01
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: IK1ODO beacon signal
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Hello Marco,

I will see what I can do to adapt QRS, I will have to use the parallel port
for power switching as all 'output pins' off the serial port are alrteady
in use.
Alternative I could try to put some softawre in a PIC16F84 processor, I
already have some 'beacon software' for it, just have to change speed and
add the power switching. I am willing to send you a programmed PIC on a
ready-to-use PCB. This would have the advantage that you do not need your
PC for it.

Regarding power switching and the WX-related detuning :
It should be possible to built a small class-D TX and adjust the
powersupply voltage to regulate output power. If we incorporate some
feedback from the amp-meter to the voltage regulation it should be possible
to have a TX that runs at constant antenna current (= constant ERP).

The above are just some thoughts and a lot of work will be involved it we
want to realize it. So maybe we first have to check if there is enough
interest from the 'listeners side' and if we can share the work, it
wouldn't be fair if we expect you to do it all.

73, Rik  ON7YD

>>At the risk of being 'greedy' I would suggest following to Marco : would it
>>be possible to have a series a characters at reduced power after the call ?
>>eg. : 'IK1ODO X Y Z' where IK1ODO is tranmitted at 10mW ERP, X at 5mW ERP,
>>Y at 2.5mW ERP and Z at 1.25mW ERP (of course any other 3 characters can be
>>used).
>>
>>73, Rik  ON7YD
>>
>Rik, I will take this seriously. What about writing a modified version of QRS
>to command an attenuator and step power levels?
>I may build a linear amplifier, of some 10W output, and reduce the power
>in four steps of 5 dB (3W, 1W, 300 mW, 100 mW for instance).
>The big problem is to have an automatic tuning. I started the beacon
>on Thursday evening, then left home Friday, and it was raining; so I had to
>raise the power, since the aerial current was down from the nominal.
>The rain stopped on Saturday, and the antenna current rose to (probably)
>+5 dB respect to Friday evening. I was not able to transmit a fixed power
>level;
>my station currently can't run unattended (in effect, my wife was attending
>and checking for smoke, HI).
>
>I returned home by Tuesday, and found the tuning of the variometer 
>completely different from Friday.
>
>Thanks to all for the reports. I think we have to go on.
>
>Well, Rik, what signal may we use to change the power levels ? go to
>the parallel port, or use an UART on the serial ?
>
>73 - Marco IK1ODO
>
>
>