Friday, 12 May 2017

JT65 Conundrum continues

In the interest of science, and at some personal cost to my energy levels later, I rose this morning in time to see how I would get on trying to see if DK8NE would hear my signal.
In fact, I had been reported earlier but I missed it.
Careful inspection that image, if you click to enlarge it, shows that I was reported at 04:10 too.

I would expect that at 04:10 there would not be so many aircraft around, and not much Es either.

You do not usually get me in the shack at that time either, and this sacrifice on my part for the benefit of science is something I will not let anyone forget in a hurry.

26 times I have been spotted by DK8NE since 1 May, but I have not worked or been heard by any other German station.

Not that I am paranoid, but I can see why people think that there is someone listening to their phone ...

I was even spotted when I was beaming East (again, today).

I had one decode each from two other stations today and worked no 6m Es at all, but I still managed to be clocked by DK8NE ten times. I cannot work anyone anywhere with a beam, but DK8NE can receive me fine all day on his loop.

To say that I was spotted ten times actually means I called CQ ten times, and I was spotted ten times. The only occasions I was not spotted was when I cut the power or after 15:19.


Some things I seem to have established.

1) No contact so far after 15:19 on any day. Not yet anyway, but I know it works fine at 04:10.

2) I tried WSPR from 21:00 last night until 04:08 this morning. Although G4CPD was hearing me, and DK8NE was hearing local stations (so both stations were working), there was no result after 6 hours. The power level on WSPR was just a bit over 20 watts, the most that I felt I could comfortably run overnight. Probably not enough power for a fair test.

3) I have poured over information on radio horizons for aircraft. From the figures I have seen so far an aircraft at 30,000 feet is too low for a path of 1000km. However, at 39,000 feet it might be possible. The site conditions at each end are hard to factor in, especially with Ayton Hill cutting me off in that direction. This is not my field of expertise (what is?) so I may have got the calculations totally wrong. Let's say that any idea I had of ruling out aircraft scatter on path grounds alone is looking shaky.

4) Multiple modes have been suggested. Yes, I can see how one propagation method can feed into another. However, for this to keep happening 10 times spread over an 11 hour period is a bit of a tricky scenario for me to envisage.

Does any of this matter?
No, not really. It could be aircraft scatter, or it could be ionoscatter, troposcatter, or a combination, or something else. The odd thing is that the path exists for so much of the day, plus it does not coincide with Es or any other opening.

I think, having got this far, I should shut my investigation down for now and see how things go over the next few weeks. Either it will stop, or something will emerge which pins it down once and for all.

I am certainly not trying again at 04:10 tomorrow.

73

Jim

GM4FVM

4 comments:

  1. Hi Jim, I salute your sacrifice for science! Aircraft over that route regularly cruise at levels between 39,000 and 41,000ft. Perhaps it is just aircraft?

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  2. Jim,

    Have you tried Airscout software?

    It takes into account the path profile, so Ayton Hill etc. It will also show how high the aircraft would have to be and where.

    I will have a look too, as he sees my signals on 50 MHz too. Both MSK144 and JT65.

    I just was thinking what a fantastic resource we have with DX Maps and PSK Reporter. The power of crowd sourcing come good for science. It just needs some discipline by users of MSHV from sending rogue spots apparently coming from the wrong band, ruining it for everyone. My opinion, MSHV should NOT send PSKReporter spots unless it is using a CAT interface to get the band and frequency information from the transceiver.

    Other things like some of the Australian amateur back scatter bistatic radar experiments that were able to see not only back scattered single hop Es ground reflections, but multiple hop ground refelections, and round the world echoes, and even multiple round the world echoes! Our signals go a lot further than we think at times.

    I wonder who will be the first to detect earth-moon-earth-moon-earth signals? I believe it may have been done with Arecibo, but not with UK amateur power levels :-)

    73

    David GM4JJJ



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  3. I did some experimenting of my own this afternoon Jim. I was coming back from Munich overhead Amsterdam at 38,000ft and dialled up the St Abbs VOR which is just up the road from you. The receiver picked it up 280nm from the VOR, this equates to 518km. So given that the aircraft could be a reflector you may well get your 1,000km distance to DK8NE.

    The airspace at the equidistant point of your contact is managed by Maastricht control and Scottish Control. It is some of the busiest airspace in Europe with heavy metal like the A380 superjumbo which cruises at 41,000ft cruising through the airspace so I suppose there maybe a fair chance of it being responsible for your being spotted at DK8NE.

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  4. Gavin

    Good man, thanks. I was hoping that a chance like that might turn up, and I appreciate you taking the time to do it. I was not expecting you to act so quickly! Well done.

    It more or less confirms what I had found, but my site is not as good as the VOR. The figure I had was 488km for 39,000ft, but my own horizon was only making up 38km of that. With a better site and a higher mast you could easily reach a combined figure of 518km. I also thought that the elevation of DK8NE's site would increase the effective maximum distance in his direction and bring any sweet spot closer to me than the mid point.

    I know that David GM4JJJ was also getting spots on what must be a 50km longer path.

    So that looks like a runner.

    Once again, I wonder how this path has existed for so long and I have never noticed? Clearly there are enough aircraft to make it viable.

    What I would like to do after the Es season has finished is try some aircraft scatter with a station located along the same air corridor. I would guess that 1000km is a good distance. I must check the corridor to see what might be the best places to look.

    So, next questions are, what about 2 metres and what about other modes?

    Once again, thanks for doing that. There is nothing like an actual observation to confirm any theory.

    Jim

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