In addition to pointing the antenna directly at the satellite and determining the offset of the downconverter frequency there is a third large variable in being able to receive mode S.

I have received full quieting signals with a 6 1/2 turn helix when AO-51 is above approximately 35 degrees elevation.

This evening I tried a QSO with Dave G1OCN when we both had a max elevation of 5 degrees. I could hear him and myself for over a 3 minute period but he did not hear himself or me.

I was receiving with a 1.2 meter dish which has about 14 db +/- more gain than the 6 1/2 turn helix. With the dish the AO-51 downlink signal is +10 db over S9 when the elevation is above about 15 degrees. The AO-51 signal at 4 degrees elavation was S5 +/- QSB. This is again a difference of about 14 db. (S meter checked with a signal source and step attenuator)

This 10 to 15 db loss in signal level at very low elevation can be partially attributed to increased range but primarily due to the off pointing angle of the S band antenna on AO-51

Farther measurements would likely show considerable variations in the S band downlink signal level relative to elevation and azimuth.

Clare VE3NPC

No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.362 / Virus Database: 268.12.4/449 - Release Date: 9/15/2006