Hi all.

I had this test reports with G3XIZ. 3 reports on day time around 1100 TU and others at evening from 1820 to 2004 TU. For this RX test, the antenna was a 9 m base loaded vertical tube without top hat, RX FT1000MP and no preamplifier.

As expected, the evening  G3XIZ S/N computed by the WSPR at 422 km distance shows a regular drop. You can see also that the reports around 1100 TU gave  10 to 15 dB better S/N.

I made 3 mesurement of the noise level using my Peggelmesser SPM3 :

• At 1050 TU : 40 µV   band noise, the sun site in my QTH was 59° ;
• At 1830 TU : 120 µV band noise, the sun site in my QTH was 10° ;
• At 1956 TU : 250 µV band noise, the sun site in my QTH was -3°.

Conclusions :

• The signal level stay the same, but the band noise increasing explain the drop in the S/N computed by WSPR ;
• At 422 km the site angle for a single hoop is about 45°. That is over the value of the pseudo Brewster angle on that frequency, and the back return efficiency is below 10 dB !
• The increasing in noise is due to the drop D layer absorption.

Well, that is not a scoop ! Have a look at the 30 / 40 years ago LowFERs States experimentations on the 1875 meters band and after on the 1750 meters band. Some very good informations about that was published in old issues of QST and more in CQ magazine.

73 de Andy.