[ARC5] LDE

Thu Jul 18 21:47:52 EDT 2013

LDE's don't have timing "rules" per se.  But if you buy into the ducting 
theory then timing is determined by an integer multiple of loops around the 
earth.  Documented cases of LDE's with timing measurements back this up.  I 
am not aware of any path "rules."

** Ducting is well known on VHF and up but isnt fully understood at MF and 
HF. Most of the LDE's Ive read about followed no timing constant either

As for long path involving sunlight, that is possible as long as the path 
doesn't involve a lot of sunlight..  The long path from California into 
Eastern Europe and the Middle East is actually not straight most of the 
time.  It bends around the sunlight edge of western Antarctica in the 
wintertime (summer in Antarctica).  The theory is that the ionization 
gradient that exists vertically along the terminator can refract waves 
latitudinally.  This has been verified by hams that can rotate arrays on the 
lower bands.  We're talking a 15 degree or more deviation from the great 
circle route for the long path.  I have experienced this myself on 40M even 
though my antenna is not rotatable.  But it does have a good null in the 
great circle direction of stations I have worked repeatedly with good 
signals.  The best explanation I can come up with to explain my results is 
this bending theory.

** As far as my 40M experience it was with a stacked pair of KLM 4el 40M 
yagis with one at 180' and another at 60'. Either or both could be selected.

Im well aware of propagation and the known theories and have over 300 
countries confirmed on 40 and 80,20, and 10 for that matter. Only about 290 
on 160  (-;
I also use a Grayline program and can guarantee you there wasnt a chance in 
hell that the LP was grazing the dark side. That morning was discussed at 
length since it was widespread and the conjecture was a skewed path going SW 
that swung back over Indonesia and continued up the Pacific rim to northern 
Asiatic Russia. So coastal ducting was obviously involved for a part of the 
path based upon what was all being worked. I worked Indonesia and Brunei 
that morning as well as several JA and UA0's.

On VHF it would simply be called scatter or multipath but because of the 
distance someone had to come up with another name to add to the confusion.
Ive worked Europe peaking over South Africa on 6m and Africa peaking over 
the Caribbean. Sounds strange but its rather common sidescatter and also 
happens on 10M.

I thoroughly agree with your last statement.

Carl
KM1H

Whatever is true, I think propagation is fascinating.....because its part 
science and part mystery.

Dennis AE6C

On Thu, Jul 18, 2013 at 5:39 PM, Geoff <geoffrey at jeremy.mv.com> wrote:

Long path would be SE and it would have been all sunlight, that is not 
possible to support a 40M contact.

The paths I experienced were multipath with both in darkness and I havent 
read that there are any specific paths or timing rules required for a LDE.

Carl

----- Original Message ----- 
From: Dennis Monticelli
To: Geoff
Cc: Kenneth G Gordon ; ARC-5 Maillist
Sent: Thursday, July 18, 2013 4:01 PM
Subject: Re: [ARC5] LDE

Geoff,

Your experience on 40M sounds more like simultaneous long and short path 
than LDE.  LDE delays are integer multiples of dah length. The delay due to 
short vs long path is about a dit at 20 to 25wpm.  That means the dits from 
the long path perfectly fill in the spaces between the dits over the short 
path.  Inasmuch as short path vs long path strengths can be nearly equal 
over a short stretch of time, copy becomes damn near impossible. I have 
heard this phenomena many times over my ham career and several times just 
this past winter on 40M at sunrise while working Europe.

Dennis AE6C

On Thu, Jul 18, 2013 at 10:55 AM, Geoff <geoffrey at jeremy.mv.com> wrote:

Ive heard LDE's many times from 80-15M as I was obsessively active for 
decades. The strangest was on 40M one morning just past sunrise when Asiatic 
signals from JA, UA0 and similar were arriving stronger from the SW than the 
direct NW path and after their weaker direct path which had intense auroral 
flutter. If it wasnt for the yagi I used copy would have been very hard. 
Comments on the DX Packet Cluster from many with verticals and wires was 
that they couldnt even copy their own calls.

Carl

----- Original Message ----- From: "Kenneth G. Gordon" 
<kgordon2006 at frontier.com>
To: "Dennis Monticelli" <dennis.monticelli at gmail.com>
Cc: <Arc5 at mailman.qth.net>
Sent: Thursday, July 18, 2013 1:16 PM
Subject: Re: [ARC5] LDE

On 18 Jul 2013 at 10:01, Dennis Monticelli wrote:

Ken,

On what band did you experience this LDE?

Yes. I forgot to mention that: it was on 80 meters, around 3580 Khz, as I
remember it.

 I have heard LDE's on the
strong signals of local DX'ers on occasion.  The band was 20M.

Hmmm...that second one I heard may have been on 20 meters...

LDE's occur in integer delays of approx 128ms as I recall (the time it
takes for a signal to circumnavigate the earth).  Yes, ducting is the
theory usually offered.

Thanks, Dennis. As I said, that explanation really doesn't satisfy my mind 
on
it, but it may be correct.

Ken W7EKB

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