Dear Rik, LF Group,
At 10:30 08/04/2003 +0200, you wrote:
A friend of mine is interested in QRSS tests on 10.1MHz (30 meter) and one
of the things we are discussing is the longest useable dotlength is on
that frequency. Apart from TX (and RX) stabilty doppler shift due to
ionospheric refections will cause frequency instability
Based on the experience of receiving the US "Hifer" beacons on about
13.55MHz last year, doppler shift of a few Hz can be expected - sometimes
the traces are blurred, or even split into 2 separate traces a few Hz
apart, but QRSS3 seems to work fairly well - I suspect a dot length longer
than 3s would be counter-productive due to the generally much greater
doppler effects at HF, and the rapid fading.
The Hifers were often visible last summer during the night, and
occasionally even audible using a dipole receiving antenna. I think they
normally run a few mW into ground-plane type antennas, which is a nice
demonstration of how much easier HF is!
Cheers, Jim Moritz
73 de M0BMU
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