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AO-40 Mode U/S 1st Impressions



The setup here is a Drake 2880 + Conifer preamp + 16-turn helix.  Uplink is 
50 W + 25 m of 9913F + 10x10 hombrew antenna (800 mm boom).  Noise level is 
between S0 and S1.

50,000 km - I was asleep.
42,000 km - beacon at S2, weak CW signals, inaudible SSB detected, could not 
find my downlink
40,000 km - beacon at S3, 549 CW signals, a few strong SSB stations 
comprehended, heard a few weak pings from my station
39,000 km - beacon at S3+, my first SSB contact with W1BFN.  He was 33 w/.QSB
35,000 km - beacon at S5, signals steadily improving, but still with QSB
30,000 km - beacon at S6, strong SSB signals, passband full of happy ops
25,000 km - even better

Only the strongest uplink stations could be heard at first:  KB8VAO and N1JEZ 
among the best sounding signals.  Both had L and U uplinks.  Both indicated 
the U uplink was stronger.  

There was a wide disparity in downlink capabilities, but even at modest 
altitudes of 35,000 km and less, an AO-10-class 70 cm station seems to be 
required for a solid signal (at least with this AO-40 configuration and power 
level).  This was surprising, but many people struggled to get a return from 
the bird.

The IRC support group was a very positive affair and ops went out of their 
way to be helpful.

Changing circular polarity on the 70 cm uplink was required often to maintain 
a consistent signal (at least at my ERP).  This was also surprising and I 
can't help but wonder (again) if downlink CP switching is going to be 
helpful/needed for marginal setups.

73,
Jerry, K5OE


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