LDE?

[Kim Elmore]

I've been lurking here for a few years and enjoy reading all of the wonderful things done by the group. I use citizen science myself as I'm the project scientist for the mPING app. Today I have an HF propagation questions that has puzzled me for quite some time.

Today at about 1745 UTC on 15 m, I noticed what may be a long-delay echo: my transceiver is a TenTec Orion II running full break-in. When my antenna (KLM KT34A, roughly equivalent to a 3 el yagi) points eastward (30-139 deg) or westward (200-300 deg), if I send a dit I hear its echo. It gas to take long enough for the rx to recover, so from what I've read that counts as a long-delay echo. I would notice this occasionally when I live in CO and worked for NCAR (I'm now at OU working with NSSL as a research scientist) and this isn't the first time I've heard it here. This time, it occurred to me to ask people far more knowledgeable than me about the ionosphere and propagation: what's going on? What process might explain what I'm experiencing?

73 & Happy New Year,

Kim N5OP

--

Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP SEL/MEL/Glider, UAS, N5OP, 2nd Class Radiotelegraph, GROL)

“People that make music together cannot be enemies, at least while the music lasts." – Paul Hindemith

[Phil Erickson]

Hi Kim,

Does the delayed dit sound different, as in dispersed? It would be interesting to try a continuous reception on a nearby SDR to see the difference between the direct and delayed echo as well. If you have a directional coupler available, you could also put that on a scope to see the difference.

Recording it and sending it to the list would also be useful.

73

Phil W1PJE

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Phil Erickson
phil.e...@gmail.com

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[Ethan Miller K8GU]

Kim,

First--concur with Phil's requests for a few details.

My initial thought is that it might be a "round-the-world" (RTW) echo,
which usually has delays of 100+ ms. Those are commensurate with
(greater than, really) fast CW element and T/R turn-around of a good
QSK rig. If you could get some audio or RF samples, we could confirm
that. I may have mentioned it on the list before, but it bears
repeating: there is a very good book that summarizes the state of the
art for RTW and long-distance (DXer type) HF propagation: A. V.
Gurevich and E. E. Tsedilina, Long-Distance Propagation of HF Radio
Waves, Springer-Verlag, 1985. For the technically-inclined amateur,
really only the first chapter is necessary, but it's all very
interesting.

I haven't been as active the past week or so, but certainly, through
the early part of December, I chased some European special event
stations (DL2025* and HG100*). In the later morning here, probably
around 1600 UT, they would often be beaming E or NE on 20 CW (toward
Asia; two of the operators confirmed this). They had very significant
RTW sound when I was beaming short path. I actually worked a couple
of them long-path because the signal was better and the echoes much
less severe. One of the ops commented that I was much louder on 15
(SP) than on 20. He got a huge kick out of it when I told him I'd
worked him LP on 20.

73,

--Ethan, K8GU.

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[Kim Elmore]

Hi Phil,

That's a great question and one that I can address in only approximate/qualitative based on ears.My receiver doesn't recover fast enough for me to effectively hear the start of the echo. but the end sounds as crisp as any other signal. Because it's so short, I can't assess fading continuously but if I send a fast (50 WPM) dit every half second to second (think of a 1 s time series sample), I can hear that there is definitely fading.

What you suggest is most certainly needed, but I don't have a coupler or the rest of the necessary equipment to do it.

73 & HNY,

Kim N5OP

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[Kim Elmore]

Hi Ethan,

Thanks for the book reference! I need to snag a copy.

LP is certainly RTW propagation by definition. I have a TS-930 (alas, currently out for service) that has a much faster RX recovery. When I heard this using the '930 in CO, I became convinced that I was hearing RTW echoes because, by varying the keying speed, I determined that the delay was about 100 ms (a bit longer, actually). My determination was very crude: I'd manually adjust the keying speed until the keyed dit exactly masked the echo, then converting the delay between dits to seconds based on the keying speed.

I've only ever heard this at my station and with my antennas on 15 m. I've never heard in on 20 m and until recently didn't have a directional antenna for 12-17-30 m; I recently put up a 2 el antenna for those. I didn't think to look for this on 17 m but I will the next time it happens.

73 & Happy New Year,

Kim N5OP

I wish I could provide more information about it; I'm simply not equipped to provide it.

[Phil Erickson]

HI Kim,

  I know that Ten-Tec equipment has very good fast QSK break-in.  This post:

https://groups.io/g/TenTec/topic/t_r_switching_issue_on_orion/76243191

  has a couple video links to a person who had trouble with a perhaps malfunctioning Orion II QSK delay of as much as 0.5 seconds.  How long is yours?  Do you also have the menu setting to minimum delay in the QSK area?

  The back end crispness seems to indicate that we don't have dispersive delay going on (as one might expect if irregularities were also involved in the propagation), but I think Ethan might have more insight there into how much dispersion one would expect.  Certainly, given RTW travel distance, there's no way it is getting back to you faster than 100 ms.  Perhaps this is just stock LP type echoes.

  Is there a KiwiSDR in your vicinity?  That could be experimented with to see if you can detect the SP and LP echoes separately if you are fortunate enough to have one nearby, although of course not ideal because it doesn't have the antenna gain of your system to help it.  But worth a try.

http://rx.linkfanel.net

73

Phil W1PJE

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Phil Erickson
phil.e...@gmail.com

[David Eckhardt]

From experience:

The first time I experienced true LDE was when I was a much younger critter.  We lived in Lansing, Michigan and I was on 20-meter CW calling CQ at roughly 20 wpm.  I was amazed to hear the last three letter of my ID come back to me, a bit watery.  I was operating only a 40-meter meter dipole using an NCX-3 at roughly 80 or so watts output.  Remember, these were tunable pi-networks, so it loaded up OK on 20-meters.  My call was K8SLK and I heard the last dit of the 8 and the complete SLK and the k following that.  I repeated several times to confirm I was not imagining things.  I wasn't as the repeat sounded about the same.  I've heard it other times, but not so long and prevalent.

Another event on 75-meter USB, again about 100-watts.  We had a weekly net between Corona and Orange County.  Then one of the OCites asked me if I had an echo chamber.  I didn't.  We got three to five echoes of individual syllables, not as long as my original experience, but quite strong.

OK, I've heard LDE's mostly on 40-meter CW as that's the band I mostly use and monitor at present.  None have been as strong as my original experience on 20-meter CW.  All 40-meters have been shorter and not as strong.  

Something different using the ECHO application as part of the WSJTX suite, I tried 160-meters at 5-watts.  Sure enough, an echo reported at roughly a 135 ms delan.  I both reduced and increased my power by 3 dB.  In all cases, the reported S/N reduced and increased by roughly 3 dB (within 0.5 dB of the original at 5-watts).  Sure, this is circumearth propagation, not true LDE.  Two other hams in Berthoud, Colorado repeated the same experiment with similar results.  I've also done the same on 80-meters with similar results.  Again, not ture LDE.

All the genuine LDE I've experienced have occurred during minor to so-so disturbed conditions.  We lived in Albuquerque when the Los Alamos bunch finally explained what causes LDEs - ringing back and forth in a magnetic bottle located in the magnetosphere (very brief of brief explanations).  Entrance and conjugate points (the reflection point) must be properly aligned to form a genuine LDE.

That's enough from me.  Others and myself in the Northern Colorado region have repeated the circumearth tests several times using ECHO with very similar results to our original attempt. 

Dave - WØLEV   

   

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[Ethan Miller K8GU]

Dave and Kim,

Great stories--yes, the "real" magnetospherically-ducted LDEs are much
rarer than RTW and generally occur at lower frequencies (like 75m).
RTW during the daytime is usually above 15 MHz--but, the book I cited
reviews the literature and climatology as it was known in 1985. In
the US, it was the Stanford (SRI) group that did a lot of work on the
subject in the 1960s.

Kim, hope you get your TS-930S working again. I sold my two 15 years
ago to buy Elecraft gear, which I do not regret. I did end up with a
basket case TS-930S from W8AV that's sitting here on my "spare"
operating desk behind my telecommuting rig. I tore the whole thing
down last winter and made a lot of progress on it; but, it has some
"interesting" idiosyncrasies that I've been trying to get un-done,
including a mixture of boards from before and after the 3-million S/N
major redesign. It has the PIEXX board and I bought a roofing filter
when Inrad was clearing them out (I had one in one of my old
930s...great upgrade if you don't care about AM). Eventually, I'll
have another nice radio.

73,

--Ethan, K8GU.

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[Kim Elmore]

Hi Phil,

There isn't a KiwiSDR near me that I know of. The very few times I've actually worked anyone LP it's never been over a polar path, so There's no auroral quality to the signals. That these are heard from E-W directions -- I failed to mention that the signal I hears was stronger when I was pointed E than when I was pointed W -- must be significant. I'm now quite convinced given what I'm reading that what I hear is my own LP signal and not  true LDE.

My QSK is set up to be as fast as it can be without clicks. But it's not fast enough to hear anything between infra-character elements fsater than about 40 WPM. The TS-930S has much, much faster QSK because it's hardware not software.

73,

Kim N5OP

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[David Eckhardt]

For what its worth on 40-meters:  Over the last week++, the PACRIM broadcasters have been coming into Northern Colorado over the pole quite regularly during mid to late afternoon.  A lot of auroral flutter, of course.

Dave - WØLEV

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Dave - WØLEV

[Kim Elmore]

Hi Ethan,

I do, too. I bought it new in 1986, so it's a late S/N unit. It has the PIEXX board, the K6IOK PSU, and PA in it, along with the Inrad roofing filter, making it a pretty bullet-proof FD rig. While  I very much like my Orion II, the ergonomics of the '930 are the best I've ever used. It's in Dave Phillips's shop and I think he has a *huge* backlog.

73,

Kim N5OP