Re: LF: Re: MF propagation

[DK7FC <73dk7fc@googlemail.com>]

Hi Alan,

Am 21.05.2014 13:41, schrieb Alan Melia:

A few more simultaneous reports would be very interesting. :-))

That would be no problem if there were enough WSPR stations monitoring day and night, and transmit day and night. I am one of them but that's not enough i think :-)

73, Stefan


Am 21.05.2014 13:41, schrieb Alan Melia:

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 -----

From: DK7FC

To: rsgb_lf_group@blacksheep.org

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 -----

From: DK7FC

To: rsgb_lf_group@blacksheep.org

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