[Lowfer] [600MRG] WE2XGR/2 mid day groundwave competition

[John Andrews]

All,

I was distracted by other things, but did some playing with Jay's tests. 
At 71 miles, the big problem is reducing the signal!

My first approach was to use a 2-foot diameter untuned loop inside the 
shack, fed through an attenuator into the receiver. When Jay did his 
QRSS30/WOLF tests, the attenuator was set for 11 dB. Since the loop 
hardly represents a 50 +j0 Ohm source, the attenuator setting is of 
course suspect. In this case, I got WSPR copy at 0 dB setting on the 
attenuator (produced a -30 dB SNR in a 500 Hz BW in WSPR). But any 
attempt to increase the attenuation resulted in loss of WSPR copy. It 
was also clear that Jay's SNR here was not constant. I could get WOLF 
copy in a reasonable time with 6 dB cranked in on the attenuator, but 
time prohibited going any further.

The try after lunch was to use the main antenna through a large amount 
of attenuation, and WOLF was so obscenely better than WSPR that I won't 
quote the figures.

The problem here is that an attenuator on the main antenna reduces both 
the signal and the outside noise, and that's not a real-world situation. 
On the other hand, a small antenna in the shack is subject to varying 
noise levels from inside the house, and work over a period of hours is 
not too valuable.

When Jay and I have done mode tests in the past, I have varied the 
transmitter power (with a calibrated attenuator) while Jay held his 
receiving setup constant. This has better represented reality, and we 
could easily backtrack if we sensed anything wrong.

John, W1TAG