Unusual Band 2 signals

During the big Sporadic E opening on 12th June, I noticed some unusual signals on Band 2. This was only noticeable because I was running an SDR and is more a visual effect than anything else, but it’s not something I’ve ever seen before?

First of all, here is a screenshot of what I would consider to be normal Es signals:

Band 2 Es signals, from Spain

Band 2 Es signals, from Spain

Apart from the large red signal near the centre (RTE R1, at 88.2MHz), almost all the other signals are from Spain, via Es. The signals are fading in and out over time, but look quite ordinary. The VFO is tuned to a station on 88.6MHz with a PI code of E212, and a PS (seen earlier) of RNE-CLAS, i.e. “RNE Radio Clásica, Confrides/Aitana” in locator IM98.

A little earlier this is what the screen looked like, unfortunately slightly clipped by the screen grabber:

Unusual band 2 Es signals, from Spain

Unusual band 2 Es signals, from Spain

Note the strange wishy-washy fading effect, which appears to be extremely frequency-selective. Parts of the *same* radio transmission appear to be fading differently from others, giving a slanted look to the signals. I’m wondering what the propagation effect is that causes this: perhaps some multipathing?

1 thought on “Unusual Band 2 signals

  1. John Maatthews

    Hi Mark
    A very interesting observation. What is facinating is the fact that the slope changes from a positive to a negative one within a very short space of time and across the 75kHz deviation of the FM. I wonder if it is a multipath type of effect similar to the phase shifting that can be found on auoral signals. However, I am no expert on these things. I reckon someone really smart, like Peter Martinez would have an answer!
    73
    John G3WZT

    Reply

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