2016-10-19, 22:32
(2016-10-19, 17:55)DrRobin Wrote: The signal strength of the interference is even stronger now compared to the noise.
The noise floor is roughly the same just under -72, but the absolute level of them all has gone up by 18 dB (assuming nothing has be tweaked anywhere between the plots). Now is that noise floor the actual noise floor of the receiver or of the iPad? What happens to the noise floor if you short the input? It ought to fall if you are seeing the noise floor of the receiver. The VLF transmitters going up in level and others being detected means that the receiver has better sensitivity. It should therefore receiver fainter signals.
(2016-10-19, 17:55)DrRobin Wrote: I can also see two new sources
20.3kHz (Isola di Travolara, Italy?) -60dB (15dB over the noise)
23.4kHz (Rhauderfehn Marinefunksendestelle, Germany) -80dB (10dB over the noise)
(Frequency data from http://www.mwlist.org/vlf.php)
Not sure that site is particularly up to date it only lists 81 kHz from Skelton. The VLF from Skelton started in 2001 and other sources (including these forums) have 81 kHz GYN2 as Inskip.