[ARC5] LDE

[Dennis Monticelli]

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."

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.

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 <dennis.monticelli at gmail.com>
> *To:* Geoff <geoffrey at jeremy.mv.com>
> *Cc:* Kenneth G Gordon <kgordon2006 at frontier.com> ; ARC-5 Maillist<Arc5 at mailman.qth.net>
> *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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