Thanks a lot Paul! Great to have a figure for Cumiana as well - I assume that was obtained by undoing the known keying and then measuring carrier SNR? There's currently an interesting but perhaps doubtable ~10 dB peak on Renato's 50 uHz grabber. This level seems to be roughly consistent with your measurement, so maybe it's real. 

At this time I'm still transmitting and the coil is beeping away, not loud enough to be annoying. I noticed that the antenna current was about 10% lower early this morning than at midday, and went down again after nightfall. It's not a matter of tuning as I'm keeping the antenna on resonance. Strangely the coil resistance seems to have increased (rather than decreased) when the temperature dropped from ~ 0 to -10°C. I would also have expected lower dielectric losses from a deeper frozen environment. One explanation might be that eddy current losses in the multilayer coil increase with conductivity (proximity effect). Or, perhaps more likely, the coil contains some ferrite chunks whose losses might have a negative  temperature coefficient.

Best 73,
Markus (DF6NM)
 


-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: So, 22. Jan 2017 21:06
Betreff: Re: VLF: EbNaut 8270.1 Hz, carrier 8270.0025 Hz