Posted by
David Honey on
Dec 01, 2006; 12:36pm
URL: http://elecraft.85.s1.nabble.com/One-Way-Propagation-tp441379p441386.html
At 10:39 01/12/2006, Tom Althoff wrote:
>Consistantly over the past 40 years I reaffirm on a daily basis
>that, at least on 40M, as the sun lowers in the west I can hear
>European stations about 45 minutes to an hour before they can hear me.
>
>I have no explanation for it but suspect that the signal level is
>the same on both ends but the background noise from the daylight
>side masks the signal as it appears in Europe.
I think that Tom has made an important point here. Our ability to
copy is based on the signal to noise ratio. I think that the path
loss will be the same in both directions. However, if the
transmitting station uses more power or the receiving station has a
lower noise level, then the ability to copy will be markedly
different in each direction. Local band noise, QRN, QRM and so on can
make a big difference. Using a directional antenna for receive can
greatly improve S/N. One thing that I regularly notice as 20m starts
to close to North America from the UK is that while overall signal
strength can fade over half an hour by 2 or 3 S units, the band noise
also drops, so sometimes readability is hardly impaired. Eventually,
of course, the signal level drops to the point where S/N is degraded
and then you have to wrap the QSO up fairly quickly because it
disappear within fairly quickly after that.
Seasons greetings,
David, M0DHO.
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com