Topband: K7RAT/B signals at W2RU - Day 2

[W2RU - Bud Hippisley]

I didn't get up early enough again this morning to catch the full pre- 
sunrise to daylight transition here, but I did notice one thing that I  
hadn't thought about previously.

This morning I had a moderately heavy steady QRN level -- presumably  
from scattered thunderstorm cells over Lake Ontario and what appeared  
to be a solid mass of T-storms over western KY -- both darkness paths  
from here at the time.

When I first turned the rig on at 0945Z I could hear the beacon on  
1999.5 but not on 1800.5.  After a short kitchen break to get my  
morning cup of tea, I determined I could intermittently hear the  
beacons on both frequencies, but never well enough for useable copy.   
However, by the time I quit listening at 1015Z, my overall subjective  
sense was that the 1999.5 signal had, on average, been audible  
substantially more of the time.

However, while I was sipping my tea, it occurred to me that the  
difference in background noise levels at the two ends of the band this  
morning seemed to be closer to 12 dB than yesterday's 6-8 dB.  How  
much of that, I wondered, is due to "tilt" in the noise spectrum of  
the T-storms that represented the dominant noise mechanism this morning?

Which leads to these questions:  What is the usual tilt, if any, in T- 
storm noise across 160?  Is it consistent from storm to storm?  We  
know T-storm noise content falls off with increasing frequency, but it  
also peaks somewhere down low. If the peak is below 1.800 MHz and if  
we can generally assume a downward tilt in T-storm noise generation as  
we go up toward 2000, then wouldn't audible T-storm activity on a  
given path suggest a bias toward use of the high end of the band?

Bud, W2RU