A question perhaps for Paul or yourself follows:
At ~0.22 fT (estimated from Paul’s spectrogram) I expected to see >> 10dB SNR in 278uHz. 10dB SNR is off scale so I looked at the on/off tails and noise, and I still seemed to be off by a substantial amount in the relationship of flux density and SNR in Paul’s spectrogram, but I had not factored in sferic noise and cancellation.
If I assume 30fT/rt-Hz for sferics, and 20dB sferic noise cancellation in a clipper, then a 0.22fT signal (with 3.0 fT/rt-Hz sferic noise after clipping) would yield roughly 13dB SNR in 278uHz, which seems consistent with Paul’s spectrogram.
My question is:
Is 20dB noise reduction a reasonable estimate for the sferic clipper/blanker?
I think that I had become accustomed over the winter to seeing near-preamp-noise-limited SNR on a number of VLF receivers, notwithstanding sub-fT/rt-Hz preamp noise levels, and that may explain why I was expecting >>10dB SNR for ~0.22fT and noise in 278 uHz. If Paul considers the sferic clipper/blanker noise reduction to be roughly 20dB that would explain my overestimate.
Nice signal from your (9m?) antenna!
From: [email protected] [mailto:[email protected]] On Behalf Of Markus Vester
Sent: Tuesday, April 19, 2016 1:25 PM
To: [email protected]
Subject: VLF: 8270.0025 Tuesday Apr 19
After a couple of minor modifications (different soundcard, thicker piece of wire from the top of the loading coil), I ran a test carrier from 13:15 to 15:15 UT. I briefly ventured pushing the drive up to 0.42 A (= 30.0 kV rms) with no adverse effects, but then settled to 0.35 A to have a bit of margin for the long transmission. Unfortunately not much appeared in Heidelberg and Breclav in the upcoming afternoon QRN. But then, looking at Paul's spectrogram saved my day: