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WSPR testing an inverted-V Yagi


WSPR test of a wire Yagi antenna
Malen, VE6VID has built a 20m, inverted-V, 2-element wire yagi antenna, and asked Ken VE6AGR and Ian VE6IXD for some help in testing its performance. We set-up Malen’s Yagi and Ken’s inverted-V dipole near a parking lot just outside Calgary’s international airport.
Both antennas were powered by WSPRlite devices, 200mW and 50% duty cycle. They were started simultaneously and run for just over an hour. The experiment was run twice, on the second occasion Malen improved the SWR of his antenna by adding a hairpin match at the feed-point (see picture).
Using DXplorer, the following data was collected; the 78 spots detected for Ken’s dipole; the 64 spots detected for Malen’s Yagi; the 64 spots simultaneously detected for both antennas. We also collected the images for the DX10 metric, the difference in power for simultaneous spots, and the map showing where the spots for each antenna were received.
The summary is that neither the DX10 metric, or the difference in power of simultaneous spots showed much difference. However, using the “spots map” and hovering over each spot, I was able to obtain the difference in power received at each location. Writing this on a print of the map showed clearly that the Yagi was giving higher power in the direction from Calgary towards Arizona and southern California, and that the inverted-V dipole was obtaining more spots (and slightly higher power) eastwards towards the US mid-west.
The average increase in power in the SW US over the dipole, was about 2.2dB. Perhaps coincidently the same value that I obtained by modelling the wire yagi in EZNEC 5.


Can you post a link to your EZNEC file?


I have just changed from EZNEC demo. ver 5 to 6, and also changed computers, but here are .ez files that differ mainly in their spacing between the driven and reflector elements. Malen’s antenna had an 80" spacing.



Thanks for posting Ian.
Beamwidth 142 degrees, hmm. Maybe space the elements out to see what would happen.



Just an update.
The 2 element yagi has be expanded into a 3 element with the addition of a director. Spacing for now is reflector - driven is .1 wave length, driven - director .13(ish) wave. Testing with WSPR soon.