Dear LF Group,
Thanks for the reports on last night's tests. It is nice to see that it is
possible to maintain the timing and phase of the signal over quite long
periods of time, and that Andy's demodulation scheme works first time.
For long distance communications, it will be interesting to see what effect
sky-wave propagation has on the stability of the phase of the signal - I
suppose this could be investigated by looking at some of the stable
broadcast signals thare are around - MSF, HBG, Droitwich, etc. Using this
type of system, it should be fairly easy to see the phase changes produced
by the ionosphere moving around. An extension of the technique would be to
measure the time difference between phase transitions at TX and RX, so
determining the path length - but that would be more difficult.
I hope to do some more tests during the week with lower power levels, etc.
as G4JNT suggests. At the moment, the PSK signal is generated by simple
hard-wired logic - the length of the 12 bit "message" is fixed, but the bit
period can be changed quite easily. If anyone has ideas for interesting
experiments, please let me know.
Cheers, Jim Moritz
73 de M0BMU
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