[Lowfer] e-probe vs loop

[Garry Hess]

Spurred by Jim Davey, I've begun measuring simultaneous SNR performance 
of my e-probe and 10' shielded loop for daytime, nearby NDBs. There is a 
tremendous amount of experience out there so I'd like to hear what 
others have to say about e-probe vs loop sensitivity.

So far my procedure has been to tune in candidate NDB carriers with a 
pair of SDR-IQ receivers, one for each antenna, feeding separate PCs 
running SpectraVue and Spectrum Laboratory. The latter is programmed to 
save text files of signal, noise, and signal/noise powers each second. 
Data collection is ended after about 2 minutes (to match the SNR window 
of WSPR). The text files are input into Open Office spreadsheets for 
easy calculation of average and median values (the latter is the 
preferred statistic because it is resistant to outliers/errors).

Based on 9 NDBs sampled thus far, the 10' loop has a median advantage on 
the order of 5 to 6 dB. Variation is appreciable - the smallest 
advantage is 2.6 dB, the largest is 11.5 dB. While the absolute numbers 
change with time (as seen by measurements repeated a day later), the SNR 
values are steadier.

Future measurements (if they aren't reinventing the wheel) may examine 
the impact of e-probe length and loop size. Both antennas seem to be 
free of obvious, local man-made noise but it might be possible to 
measure performance at different antenna locations too.

-- 
73, Garry, K3SIW, EN52ta, Elgin, IL