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M0VGA's picture
Thu, 03/08/2017 - 20:59 -- M0VGA

I’m a big fan of WSPR for many reasons, normally operating a beacon on 40m at 200mW 24x7x365 and also RX using my Elecraft KX3 tied to a Windows laptop running WSPR v2.12 as much as I can - software crashes depending (sorry K1JT)…

This experiment was to see how well a basic mobile HF vertical antenna would perform for 24 hours on 40m using 200mW at my QTH. I used two of my SotaBeams WSPRlite beacons – one on the vertical antenna and another on my stock dipole antenna which runs 24x7 anyway – my stock Aerial-51 OCFD wire antenna is mounted at the “centre” point on my chimney in an inverted-V formation. The test ran from 11:00 28/07/2017 to 11:00 29/07/2017 GMT.

The vertical antenna on test here is a basic mobile HF vertical, helical wound about 2m tall placed on a tri-mag base on the lawn. I used battery power for the beacon and some basic weather protection overnight (yep, a bin bag!) as although the accompanying photos show sunshine the WX quickly deteriorated! My QTH is IO93fx – Harrogate, North Yorkshire, UK.

I used call sign M0VGA on the OCFD as per my normal operation, and 2E0WFM for the vertical on test.

Clearly the vertical was always likely to perform less well than the dipole, but what’s interesting is how the efficient WSPR protocol makes even poor antennas like a compromised vertical with no radials viable for this mode – look at the WSPR map to see the many spots throughout Europe over 24h using only 200mW of RF power!

You can observe from the “DXPlorer” graph attached how closely the vertical antenna tracks the performance of the dipole, albeit at much reduced efficiency.

I have much fun with WSPR - testing scenarios, locations, antennas, conditions etc, and it does help Hams with restricted antenna options to get some interesting DX too :)

David M0VGA

M0VGA on Twitter (@M0VGA)
M0VGA on the Ripon & DARS Blog

29 July 2017

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