From: mike.dennison@rsgb.org.uk
To: rsgb_lf_group@blacksheep.org
Date: Thu, 11 Nov 1999 09:47:24 -0000
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Subject: LF: Nighttime propagation
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On 4 Nov 99, at 10:43, G0MRF@aol.com wrote:

> Monitoring at night [in ZB2] showed an increase throughout the hours of darkness 
> peaking at 02.30 to 04.00.  Signal levels began to drop at around 2 hours 
> before dawn.
> 
> The signal level difference was around 8-10 dB in general but a peak one 
> morning at 03.45UTC was estimated at +12db on daytime levels and + 4dB on the 
> level seen between 22.00 and 00.00hrs the previous night.
> 
> The only other anomaly of note was a single deep fade 8dB peak to trough, 
> which took a full 15 minutes from start to finish and occurred between 23.30 
> and 23.45 one evening. Unfortunately I did not have the time or technology to 
> keep monitoring or recording the signal to see if this recurred on a regular 
> basis.
> 

Beware of applying HF theories to this fading pattern. That's thge 
mistake I made when noticing an unexpected fade, rather than peak, 
during the eclipse.

Because ground wave is present as well (not something we get at 
HF at any distance) any sky wave will result in =either= an 
enhancement or a decrease in signal. Both indicate the presence of 
sky-wave and are therefore potentially good news. I think this is the 
reason why there is often a discrepancy between what differently 
sited stations are hearing - often someone has reported that he 
received improved signals whilst someone else says they are worse.

I now call CQ when DCF39 is 10dB weaker than its ground wave, as 
well as when it is 10dB stronger!

As regards day and night differences, I receive the Greek RTTY at 
S9+ all night but very weak or inaudible during the day. I also 
noticed that when I worked IK5ZPV using QRSs just before lunch, 
he was inaudible, whilst at 1900UTC his normal CW was S5. Note 
that, although people have worked OH1TN during the UK daytime, 
there is very little sun to enhance the damaging D layer as far north 
as Finland in the winter.

As has been commented before, it will be useful to start some night 
time DX tests (anyone who used 160m in the sixties will remember 
the sort of thing I mean). The important thing is to coordinate 
activity. I would be willing to come on the air very early in the 
morning (or very late at night) if there were a good chance of some 
DX being around. I guess that since the QSOs will all be within 
Europe for the moment, we need a slot between 0200 and 0300 UTC 
(I am already regretting suggesting it !!!). The later in the year, the 
later the time we can have it. Perhaps a test on the second Sunday 
morning in each month in November, December, January and 
February, lasting from 0000 to 0600UTC (so you can either stay up 
late or get up early). Any takers?

Mike, G3XDV (IO91VT)
http://www.dennison.demon.co.uk/activity.htm