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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <PAEFLMFGBDKKCONLMLBIKEIECLAA.ganymede444@btopenworld.com>
Date: Mon, 23 Jul 2007 22:51:05 +0100
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Subject: LF: Re: [ 500]; Two GW's Testing...
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Status: O

Dave could I be cheeky and ask for a CD with those screens on? It is quite
difficult to get 24 hour copy of longer distance stations. I havent done the
sums but I am guessing that is too far for groundwave at this power level
and is probably much attenuated D-layer returns in daytime....but this is
what I am trying to get to grips with  :-))  Argo/SpecLab screens are not
ideal as the slope is very steep ( the dBs between no-signal and a solid
whiteline)

And no E-layer (altitude 100km) will support a 2000km single hop path
http://www.btinternet.com/~alan.melia/geometry.htm
The return is not a "mirror" reflection of course but I have had a
simulation ( by ray-tracing with a "real ionosphere" model) done for me
which gives a real apogee of 88km which yields an "apparent" reflection
height of around 100km. That was at 136khz but should be similar at 500k.

See also
http://www.btinternet.com/~alan.melia/simple.htm  for path loss
"guestimates"
I think the attenuation at 500khz is higher in daytime that 136kHz but I
have nowhere near as much data yet to judge from.

Cheers de Alan G3NYK


----- Original Message -----
From: Dave G3WCB <ganymede444@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: 23 July 2007 21:43
Subject: LF: [ 500]; Two GW's Testing...


> Rog, LF.
>
> I've got a complete set of Argo grabs of the GW3UEP beacon covering the
last
> 24 hrs. (34 MBs worth...too big to e-mail!)
>
> 1 The beacon is visible at this QTH for the complete 24h period, using
Argo
> 3 sec/dot setting
>
> 2 Daytime levels seem weak but fairly constant, presumably ground-wave
only
> propagation. Never strong enough to actually detect by ear.
>
> 3 The transition to night-time propagation commences as a series of fades
> with about a 5 - 10 minute cycle, starting at around 2200 utc
>
> 4 Signals then increase up to workable CW levels, maintaining good copy
with
> slight QSB from 0030 until 0330utc
>
> 5 Signals fall to daytime levels fairly abruptly at around 0400 utc, and I
> think Rog's central heating kicks in around then, as the frequency goes
for
> a little walk LF before settling down close to the 501.500 kHz nominal.
>
> So, the best time to work to work GW - SE England seems to be between 0030
> and 0330 utc, when presumably skywave propagation is the dominant
> mechanism....no surprises there, I guess. At this distance, it's probably
a
> single E-region hop. By contrast, the longer path to GM4SLV is probably 3
> hops or more.
>
> It will be interesting to see if the daytime signal levels hold up when
> Middle England has dried out a bit!
>
> If Mike GW4HXO is in beacon mode over the next few days, I'll try and look
> for him. Nothing seen so far.
>
> 73, Dave G3WCB IO91RM