VHF Aircraft Scatter

After the brief excitement of a small winter Sporadic-E opening last week, all has been predictably quiet on the newly installed 6m antenna. When trying to dial in the correct frequency offset for receiving WSPR I noticed Aircraft Scatter on my transmitted signal from home (IO83LS) to the remote site (IO83QV).

Numerous decodes were noticed from reflections. After further investigation, it is clear that I am fortunate (?) to live in an area of extensive aerial activity.

Trans-Atlantic traffic originating from Western European hubs such as Schipol and Munich passes over in an upper airway at high altitudes. More exploitable traffic regularly originates from Scottish airports travelling South at lower altitudes. A number of tests were performed, making use of the excellent Airscout Software by DL2ALF and Flightradar24.com.

1) FR24 was monitored until an aircraft appeared with an anticipated course that would pass through the area of interest at a useful height. EZY 1806 from Reykjavik to Manchester at approximately 19,300 feet on a track of 155 degrees looked a good candidate.

2) As hoped, the aircraft descended as it became closer to its destination. As the aircraft passed over the receive site (IO83QV) its altitude had dropped to approximately 12,150 feet on a track of 146 degrees.

3) The aircraft is now visible in Airscout, and it’s time to start transmitting. The transmit antenna is a 4 element Yagi with a beam heading of 130 degrees.

After transmitting three sequential WSPR transmissions, the results were available for review in WSPR-X (n.b. I’m only using WSPR-X for the purposes of this test – the most up to date and recommended software incorporating WSPR is WSJT-X).

No other stations decoded the primary or reflected signals – which was unsurprising due to the current flat conditions and lack of activity. Still, there remains optimism that from Spring the use of this technique could bring success, perhaps coupled with FT8.

For further background reading, I recommend reading the blogs entries of G3ZJO, G0ISW and G3XBM which contain much more detail of successful tests and to which I give credit for starting my interest.

  1. That really is good reflection! I usually only get the diagonal lines, no doubt as eveything is still at cruising height, and more-or-less overhead.

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