See http://www.hamradio.me/antennas/lnr-precision-ef-102040mkii-test-data.html for an analysis of this antenna. The antenna works very well and on 40 and 20m WSPR I was getting plenty of spots with 500mW to 5W.
|Photo on http://www.hamradio.me website of the Par antenna|
The conclusion is the earth-electrode antenna is around 9-16dB down on the EF antenna on 40m, so averaging about 2.5 S-points down. The test is not too accurate as conditions change, the earth-electrode and EF have some directivity and the reports sample size was small.