[HamWAN PSDR] Results of 7.23 mile 5.885GHz signal test

[Bart Kus]

Our primary test site turned out to be inaccessible, so we had to 
fallback to another test site.  We ended up NOT having clear line of 
sight over the 7.23 mile shot.  In fact, about 900 meters of the shot 
went through the tops of evergreen trees.  That makes this test invalid.

Having said that, the received signal strength from the +10dBm 
transmitter was about -100dBm, which is 40dB below projected values.  So 
about 105dB of path loss if you discount the cable losses.

We then hooked up the modems which run +30dBm and they were able to 
establish a 39Mbit air speed link.  Link quality was about 60% both 
ways.  Throughput tests showed 30Mbit(min) to 33Mbit(max) data 
transmission rate.  Speeds were the same in both directions.  It was 
nice and steady, with good ping times throughout.  Very well behaved 
despite the harsh conditions.  The radios reported -75dBm signal. The 
math predicts -85dBm should have been reported.  The radios are not 
calibrated measurement devices though, so a 10dB error is not surprising.

This whole test needs to be re-done with actual line-of-sight conditions 
to get a good reading on path loss in free space.  A couple sites look 
possible on satellite but need to be verified on the ground for 
suitability.  They're only 6.9 and 6.7 miles long though.  It's tough 
getting good clear long distance shots in publicly available places.  If 
anyone wants to volunteer to help out with follow-up tests, let me 
know.  If you know of a good long distance LoS option, also let me know.

--Bart