Dear LF Group,
Many thanks for the reports on the Jason beacon sigs last night from
OE5EEP, SM6LKM, I2PHD, IK2PII, CT1DRP, and to anyone else who was listening
. I started late, about 2015, after having trouble putting my antenna up -
but it went up in the end, so the ERP last night would have been close to
1W. I transmitted on 135.910 from about 2015 - 2120, and on 135.990 from
2300 - 0210. I transmitted the CW ID just by keying the TX on and off,
without interrupting the Jason frequency shifts - provided the ID is fairly
short, this did not seem to corrupt the Jason signal much, and the shifts
of a few Hz makes little difference to the CW note.
Before starting, I saw QRSS from OH5UFO just below 136.0, and between the
two transmissions I could see F6BWO active in the "T/A" slot. At this I
also heard a faily weak "digital" signal around 135.8 - It had a bandwidth
around 20Hz, didn't seem to be PSK31; maybe this is the signal Johan heard?
Perhaps Reino again? I also thought I saw another weak Jason signal at
about 135.885kHz, but although it looked about right on the waterfall
display, it would not decode, so perhaps just some jittery noise.
It is clear that Jason can be a useful LF mode. With 1W ERP, people are
getting more or less perfect copy all over Europe; I expect it would
increase the range of QRP stations in a similar way to QRSS. The bandwidth
and transmitter requirements are nicely compatible with current LF
practice, although the 100% duty cycle requires better than average
heatsinks! The software is easy to install and use. It remains to be seen
if in it's current form it is a "transatlantic" mode - The Lowfers seemed
to be otherwise engaged last night, and listening conditions over there
seemed to have been fairly poor anyway. However, a shortfall in SNR could
be made up by increasing the dot length, at the expense of speed of course.
All in all, it seems to be very promising.
BTW, does anyone know how to compare the weak signal performance of Jason
and QRSS or DFCW? It seems clear that the increased bandwidth must result
in some loss of SNR, but there will also be gains because the data is being
transmitted faster for a given dot length.
Cheers, Jim Moritz
73 de M0BMU
|
