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dxAce · July 23rd 08, 03:52 PM posted to rec.radio.shortwave

wrote:

Some of you may wonder how really long distance MW reception occurs,
such as the ! Kw Fresno CA station reported here in South Africa the
other day. This is a station over 10,000 miles / 16,000 km's away from
us.

Theoretically these signals take several bounces off the ionosphere to
get here, but the experts will tell you that theoretically such a low
power station over such a long distance will expend it's energy and it
is therefore not possible to receive such a long distance station even
on the most powerful receiving antenna.

However, it does happen and last year, 2007, various MW DXer's around
the world were getting very long distance DX the likes of which had
not been heard since the 80's. How is this possible then? Well, the
more scientifically minded hams that work 1.8 MHz have a theory that
these phenomenal long distance signals come in as a result of
"ducting". The theory is that the outgoing transmission goes up into
the ionosphere and gets trapped there, and then travels a considerable
distance before coming down to earth in some very far distant space.

That theory was expounded upon by I think John Bryant and another fellow in one
of Fine Tunings Procedings issues (sorry, I no longer have them) back in the
late 80's or early 90's.

I've not believed in radio signals making 'hops' for a very long time as it
simply does not make sense.

These signals, when they arrive at the DXer's location, are usually
very faint though and may not last for more than a few seconds, or
maybe up to ten minutes if you are lucky, so you have to be very
vigilant and alert to catch something like this, but when you do =
BINGO! - extreme joy and euphoria = lovely!

Alas, this is not the sort of thing you are going to pick up in your
suburban back yard - all these catches were made by very experienced
DXer's at prime coastal DX sites using 1000ft/300m or longer
beverages. Don't worry about the radio though, anything from a Frog
(Yaesu FRG-7) will do. The important thing with IDing faint MW signals
is to have a radio that produces a good audio spectrum that catches
all the sibilants and harmonics, or otherwise you are not going to be
able to read the signal.

If you want to listen to an audio clip of my 1410 kHz CFUN Vancouver
Canada catch 10,000m/16,000km's away, go to my good DX pal Gary
Deacons website
http://www.capedx.blogspot.com/ and on the RHS you will find the audio
clip box, then search for CFUN Canada. you will see it is very faint,
but if recorded on a decent MP3 recorder you will be able to decipher
the call sign ID with a little practise and skill.

A serious DXer can always expect the unexpected

Have fun, good luck and good DX.

John Plimmer, Montagu, Western Cape Province, South Africa
South 33 d 47 m 32 s, East 20 d 07 m 32 s
Icom IC-7700, Icom IC-756 PRO III with MW mods
ERGO software
Drake SW8. Sangean 803A
Sony 7600D, GE SRIII, Redsun RP2100
Antenna's RF Systems DX 1 Pro Mk II, Datong AD-270
Kiwa MW Loop.
http://www.dxing.info/about/dxers/plimmer.dx