Thursday, 16 April 2020

Results: VK3MO vs. VK3QN

As earlier reported, Ian, VK3MO, is currently running a long-term WSPR experiment to determine the role of low angle radiation across the solar cycle.

For this, Ian is using 5W input into VK3MO, a 4 x 5 element Yagi array on a 200 foot tower, and the same input into VK3QN, a 2 x 6 element Yagi array optimised for very low angle radiation, on a 66 foot tower.

For this comparison, both antennas are beaming long path to Europe, so my results are based on reception during the breakfast time period here.

The following plot is typical of each morning's results:


For the peak signal at long path period, VK3QN, the low-angle optimised array, which is 12 elements total, is a median 2.5dB stronger than the 20 element array of VK3MO as determined over five consecutive days.  The maximum difference between the two signals was 4dB in favour of VK3QN, and the lowest difference was 0dB.

Very interesting that the low angle optimisation of a 12 element array achieves a received signal during long path that is nearly double the strength of a 20 element array, even though the former is at considerably lower height overall.  

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5 comments:

  1. John, EI7GL16 April 2020 at 13:44

    John, do you always get two peaks from the VK3 stations? If so, why?

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  2. Photon16 April 2020 at 15:07

    Hi John. Thanks for your interest. The short answer is: 'yes'. The first eak comes a pretty consistent ~40 minutes before the second. As to what causes this, I'll have to think some more and write a post about it. But I am not expert on propagation!

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  3. John, EI7GL16 April 2020 at 16:43

    That's interesting John about the two peaks.

    For reference and you can verify this yourself. Both stations were in Kyneton, Victoria. Their local sunset was at 17:53 local. Their time is UTC +10 hours so their sunset was at 07:53 UTC.

    Is your chart in UTC or Summertime?

    I was wondering if it had something to do with short path and long path? Two peaks? I'll have to look for more info on it.

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    Replies
    1. Photon17 April 2020 at 09:13

      John, yes, both stations are operated by VK3MO; VK3QN is Ian's wife's callsign. Chart is as spots are received, which are always UT. Long path is responsible for the peak morning signal in general. The 'two peaks', which are not always so pronounced but are present, is likely to be some mix of paths. Try an area prediction in 'Proppy' or similar, and marvel at the counterintuitive paths that may be involved. I can confirm, through seaside experiments in the morning from W and E coasts, that the VK3 signals are coming from the western hemisphere, so certainly LP.

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  4. G4AKC16 September 2021 at 21:09

    Very surprised that the two lower antennas outperform the stacked 200ft array as I would have presumed that the higher stacked array would have created a variety of radiation angles that would have given a more stable signal on the long path... Presumably the long path is very dependent upon the dominant very low angle signals from the optimised lower antenna set up from these results, a fascinating experiment! ... Dave G4AKC

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Polite, constructive comment only. Any nonsense won't make it any further...

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