Topband: QSB on 160
ken.d.brown at hawaiiantel.net
Tue Oct 23 02:30:56 EDT 2007
I was probably the operator who QSOed you this weekend at KH6LC. I
operated roughly 9 hours of the contest, and Lloyd KH6LC filled in for
me when I had to take breaks. I remember a couple of runs of JAs, one of
them followed by a W1, so that was probably our QSO.
> What struck me about the propagation this night was the QSB. Peaks
> were 2-8
> minutes apart, depending on the station; the peak cycle also didn't
> seem to
> matter how near or far the station was from me. It was also strange that
> the peak signal of a station that I was trying to work did not
> coincide with
> what I gathered was my signal peak back to him; KH6LC was as strong as
> S6, but
> he was S1 when he finally copied my grid.
I would like to propose another explanation for the number of repeats
necessary for copying a grid square. I do not doubt what you say about
the period of the QSB being two to eight minutes. I think there may be
more than one QSB cycle occurring though.
Suppose that it takes you five seconds to send "FN42". And suppose it
takes me five seconds to send "AGN" or "FN??". Now suppose there is a
QSB up/down cycle that has a period of eleven seconds. If at the
beginning of our attempts to exchange grid squares, you are transmitting
during the "null" of the QSB, and I am transmitting during the peaks,
then if our exchange period is ten seconds and the QSB cycle period is
eleven seconds, it will take three to five of our exchange cycles before
you are sending during the peaks. In this case it will seem like there
is "one way" propagation, you hearing me Q5 while I keep asking for
repeats of your grid square, for about the first twenty seconds of our
attempt to pass the information. Then as our exchange cycle changes
phase with relation to the QSB cycle, it will start to seem like there
is one way propagation in the other direction.
Now suppose that our exchange cycle is still ten seconds, and the QSB
cycle is also ten seconds. In this case we would stay in sync with the
QSB, we would never get an easy copy in both directions, and you might
think I am running incredible power and have a poor receive capability.
Of course this is an oversimplification, and it is unlikely that our
transmission exchange cycle could remain constant for a long time.
Although with canned messages from the function keys of a PC running a
logging program, who knows? This does point out that one possible way to
get the exchange done is to alter the exchange cycle period, to get out
of sync with the QSB cycle. You could send "FN42 FN42 FN42" instead of
just "FN42", to get us out of sync with the QSB cycle. (You probably did
something like that)
I have always been skeptical of claims of "one way skip". There are
several reasons that it may "seem" that there is one way skip, when
there is not. Most times when one way skip is claimed, it is probably
due to higher man made noise levels at one end of the path. Differences
in transmitter power and antenna efficiencies are also factors. This
notion of QSB cycle and exchange cycle sync is another.
Having said all of the above, I have worked on many VHF, UHF and
microwave systems that employ circulators or isolators, which
intentionally DO have more transmission loss in one direction than in
the other. Perhaps that can happen in the ionosphere at MF and HF too.
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