[Elecraft] One-Way Propagation?

[David Honey]

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.