Hi Stefan, The way I try to separate ground and
skywave is to look at a beacon transmission during daylight hours. the
groundwave strength seems to correlate quite well with the minimum in the
morning and evening dips. I find tis gives similar values to those calculated by
the late G3FGQ's GRNDWAV3.
The skywave inceases in strength to mid-day at mid
path, and no there is not much if any QSB because I think the skywave is quite
stable most of the day.
Yes water does help at all frequencies in a number
of ways. There is a coast effect for station near the sea a bit like focussing.
The sea is generall less "rough" than land in terms of scattering the earth
clinging wave,and of course the loss is less
I do think the daytime skywave attenuation is
greater than at say 136 but I have no sensible measrements at 470kHz .....hence
the "query" rather than "statement" :-)) I guess about half the path
to Mike is over water as he is a lot further inland than me..A few more
simultaneous reports would be very interesting. :-))
Alan
----- Original Message -----
Sent: Wednesday, May 21, 2014 1:35
AM
Subject: Re: LF: Re: MF propagation
Hi Alan,
My observation is that the sky wave
attenuation at daytime in summer is in the order of 40 dB over that distance.
So i think it is groundwave exclusively. Also i can't see QSB over that
distances at daytime (maybe 1 dB).
Water nearly seems to act as an
amplifier at 630m :-) Could that be a reason for the choice of the ex marine
frequency? ;-)
73, Stefan
Am 20.05.2014 21:02, schrieb Alan
Melia:
Hi Stefan interesting...... at that distance
could it just be different goundwave v skywave phase at the different
receivers. You really need more thn two paths to pin that one
:-))
Alan
-----
Original Message -----
Sent:
Tuesday, May 20, 2014 12:41 PM
Subject:
LF: MF propagation
Hi MF,
| Timestamp |
Call |
MHz |
SNR |
Drift |
Grid |
Pwr |
Reporter |
RGrid |
km |
az |
| 2014-05-20 10:10 |
PA0A |
0.475698 |
+4 |
0 |
JO33de |
1 |
G3XDV |
IO91vt |
466 |
253 |
| 2014-05-20 10:10 |
PA0A |
0.475702 |
-25 |
0 |
JO33de |
1 |
DK7FC |
JN49ik |
449 |
157 |
That
shows the difference of MF propagation over sea water and over land at
daytime! (maybe 3 to 6 dB more background noise here?).
73,
Stefan
