[Lf] Observations on the N.Atantic path]

[Andre' Kesteloot]

Alan Melia wrote:

> In the week running up to Dave's expedition to the tower block, and after
> some discussions with Vaino, I have been monitoring CFH through the night
> with the strength recorded by an ADC and plotted as a graphical record. The
> set-up is far from perfect, but it yielding some interesting results.
>
> In general the comment that Dave G3YMC makes is true the best conditions for
> receiving CFH are usually in the hours between 0330z and 0530z (at present),
> when it can often be 3dB or so stronger than earlier in the night. By
> coincidence, this was not the case on Saturday/Sunday when CFH rose to a
> good level at 2300z and maintained it for about 2 hours before some fades
> set in. after about 0230 the strength declined and some very deep fades
> occured. There were returns to normal peak strength but only for short
> periods of a few minutes.
>
> Observations by Brian in Portugal and Mike G3XDV have confirmed my thoughts
> that the quietest period for us, in the East, is just on and just after
> dawn. I also noted that John reported a quiet period for a couple of hours
> after dusk. This set me thinking. Stations on the edge of the ocean will see
> different levels of noise as the shadow sweeps in. In Europe, as the dark
> shadow of dusk sweeps in it brings skywave QRM and QRN from all the rest of
> the continent ...1500kms to the east....all occupied. When dawn sweeps in,
> the skywave qrm from the east is attenuated by D-layer absorption (?) and we
> have a quiet period until the local noise sources start up. On the west
> coast of N.America and Canada the dusk will bring up the skywave signals
> from Europe up over 'daylight' noise levels, as there are only fish for
> 3000kms due East there is not much QRM. It is not until the shadow has swept
> about 1000kms inland that the skywave noise begins to build up, lasting
> probably to after dawn.
>
> If this hypothesis has any substance, it means that it may be best to
> transmit East to West at 2300z and West to East at 0500z to make best use of
> the low noise periods at the receiving station. We may have to work out a
> 'protocol' for doing that, which is acceptable as a two way contact.
> Fortunately some nights show CFH at good strength at both times
> ...Friday/Sat, and Sun/Monday being recent examples. I had thought it
> possible that the unsettled nights with the deep fades were correlated to
> high Geomagnetic activity, but the relationship is by no means clear.
>
> Well the path has now been trodden....go to it fellas.
>
> Cheers de Alan G3NYK     JO02PB
> Alan.Melia at btinternet.com