New signal in US on 27.2 kHz - TACAMO?
I happened to be looking at (my noise floor) on VLF when a new signal popped up on 27.2 kHz. It literally popped up, taking about 3 seconds to reach full power, making it #2 on VLF in Colorado, US. It was big, digital but not QPSK, although there was coherence with QPSK and the IQ decoder.
I went to TDoA and found some stations that could hear it and ran an analysis - a bit east of Hot Springs Arkansas with pretty good definition.
I checked with a Missouri SDR (not listed), thinking it would be loud at his location only to discover that it had stopped transmitting.
I've never seen this before, either the modulation nor the carrier coming and going. It isn't listed on my default Kiwi labels.
Is this a known station that only transmits occasionally?
Since writing this I've had it suggested that what we are hearing is TACAMO. If so, it may be an airborne 200 kW transmitter into a 6 mile long trailing wire antenna!
If so, no wonder it is a big signal!