Wednesday, 3 June 2020

Ebb and Flow

There wasn't an awful lot of visible QRSS to ponder about yesterday.  But, during the later afternoon, TF3HZ started coming and going on the waterfall.

It's interesting to relate how the signal changes with the structure we find in the middle atmosphere during midsummer.

TF3HZ's undulating 28MHz QRSS yesterday afternoon.

In essence, what we have is wave structure presenting a suitably-orientated reflective surface which permits propagation.  By looking at noctilucent clouds, which are reasonably considered a visual analogue of Es, we can actually see what's going on.

NLC - 'seeing' what Es looks like.  (C) 2019 MW1CFN
The wave, moving rapidly, soon changes such that the signal path is no longer supported.  And, as we all know, Es propagation is often highly localised, with one station hearing strong signals, whilst someone down the road hears nothing.

And gravity waves, which cause these undulations in Es, is the reason why this happens.

Waves in NLC and Es are rarely of trivial structure!  (C) MW1CFN

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4 comments:

  1. John, EI7GL3 June 2020 at 13:08

    Some of that drift may be due to the transmitter heating up. I get a similar slight drop in frequency at the start of TF3HZ's transmission as his TX settles.

    It might be worth using Argo on some of the 10m beacons... LA5TEN, OY6BEC. Get used to what they look like and then see if they change when there is a NLC event.

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    Replies
    1. Photon4 June 2020 at 10:25

      Hi John. I think you misunderstood the post, which is about how the signal from TF3HZ rises and falls in strength, not frequency. The trace was in fact produced by Argo.

      Delete
    2. John, EI7GL4 June 2020 at 13:23

      Sorry John, I thought you were on about the frequency changes.

      It would be very interesting to have some sort of experiment where you could see some strange effects on a signal at the same time as when you are seeing NLC clouds.

      Delete
  2. Paul Stam PAØK3 June 2020 at 18:04

    Hi John, last summer I saw for the first time NLC here in the Netherlands. It was wonderful. 73 Paul

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