Dear all.
Thank you for the various reports sent direct and in messages via the
reflector. Harmut's report from 763km is quite astounding.
The DDS driving the beacon is set to 503.700 and a quick check with a
frequency counter confirms the frequency as 503.701 to 503.702. I've not
checked against an off-air standard.
503.700 is just too high to appear on the G3YXM grabber as it's off the
edge of the filters. A quick retune from here shows it makes the distance most
of the time.
The beacon sends CW QRS3 and PSK31 messages. Two local stations Dave
G3WCB and Derek G3HEJ have decoded the PSK and kindly sent Argo screen captures
showing a small time period where the transmitter is generating 'artefacts' at
harmonics of the 15.625Hz PSK data rate.
Looking at the captures shows the offending period to be caused by the
transmission of the continuous period of phase reversals just before the PSK31
data. These phase reversals are used to lock the receivers decoder prior
to sending the PSK31 message. The transmitted spectrum appears to be double
sideband supressed carrier. - i.e. all the energy is transmitted in the
sidebands. Hence the 'interesting' Argo pics. The beacon has
been sending 9 seconds of phase reversals followed by 14 seconds of PSK31
data. It's currently off-air so I can reprogram the
microcontroller and reduce this to about 1.5 seconds, this will minimise the
generation of sidebands. (I'm also adding a key input!)
Output ERP is apx 2.5mW.
I've tried to send a URL for the beacon on a few occasions, but it seems to
be blocked by AOL or blacksheep. Anyway, if you know my website it's
listed on the index page. If you don't then it is g0mrf freeserve co uk
followed by 500k beacon htm (a few spaces need to be removed and dots added
!)
73
David
