[NLRS] COLD weather 10Ghz prop

[Bill Davis Jr]

Hello guys

  At first I was going to pose this observation to the 10Ghz mailer group 
and then I changed my mind. Perhaps there are people that or on this mailer 
and are not on the 10Ghz list that have ideas relating to an observation.

  Since the winds messed Gary W0GHZ's towers up this summer, Gary and I 
continue to "test" the 155mile somewhat obstructed 10Ghz path daily. I think 
I am seeing a pattern that I really don't have a clue about ...

Garys 10Ghz dish/system is a few feet lower than before because of the 
damage to the top section of the crank up tower, lower by 10ft of so from 
before. It seems that the path is somewhat more challenging than before. 
Under non-winter conditions, we work pretty much any time. But once the 
weather get sub-freezing the path becomes more difficult. I can almost 
always see Gary signal on the Softrock SDR IF system.. the signal tends to 
be just above the noise with  excursions to perhaps 6 or 7db above the 
noise. The signal will exhibit no scattering.. the signal will be a VERY 
narrow spike with "Normally" considerable QSO ... too weak to copy and 
sometimes to eweak to hear, but observable.

  BUT .... When the temp is well below zero at my end ... maybe -10deg F or 
colder (not cast in stone) the signal characteristics change. I see MORE 
scattering of the signal, the "spike" on the panadaptor is no longer a pixel 
wide but often is several wide, PLUS it seems often the signal is stronger 
by 5 or 6db. Also often less QSB is observed. NO observation of radar 
returns have been made under these condition. I have labeled this prop "cold 
wx tropo" in Gary and my conversations.

  Our data set is still pretty small, but growing.

  What might explain the difference in prop between +10deg F and -10deg F?? 
Gary and I again this morning (while I was at Minus 12deg and he was at 
0deg) had a nice 5-1 QSO .. this was the case several times last week when 
we were in the icebox around -20deg. Earlier this week at 10 or 12 deg ABOVE 
zero ... the  sig was observable but weaker and no Q resulted.

  On one occasion it appeared that a few deg of elevation at Gary end 
improved the signal, but this has only been observed one. There was some QSB 
during this QSO. Again no radar returns on MSP or DLH radar but Gary 
observed clouds to the north. The temp that day here was around -17deg.

  Most of the so called "city heat bubble" would behind Gary in our path, 
for what it is worth.

  Gary and I both run right at 6 to 8 watts to the feed of an 18" offset 
dish. My dish is at 56ft and sees nothing in the path for the first 3 or 4 
miles, then multiple ridges that extend into the path by about 100ft, these 
ridges are less than 10 miles from my location.

  Gary's dish is at about 40ft ... looking across "open" suburbia ...

  Any Ideas ??? or similar observations??


------------------ Activity Report -----------

  746Pro continues (after being to the factory) exhibit very objectionable 
distortion intermittently  on 2m SSB. This problem does NOT seem to 
interfere with digital communications on WSJT on EME
and MS. Odd ...SO ... I am now using the SDR 1000 / Internal 2m transverter/ 
DEM preamp on 2m
SSB (with the 400w amp)

Mostly I've been working 40&80m CW with a Vintage station that assembled 
this fall. A Viking Adventurer / Viking 122 VFO and a Hammarlund HQ-129X. 
Much like a station I had back in 1957.
A FAR cry form the Softrock SDR Transceiver I was working 40CW with last 
spring.

  Fun Fun Happy Holidays, or if you don't mind Merry Christmas!

Bill  K0AWU  EN37ed