Grimeton Radio Alexanderson Alternator 17.5kHz

Today, the Grimeton Radio VLF transmitter was run on 17.5kHz.  This is a direct generation of the radio signal by a giant rotating machine, with liquid resistor dummy loads.

Test transmission as a WAV, recorded here in IO93NR UK:

The full telegram as an MP3, recorded here in IO93NR UK:

GB3MCB 144MHz signal after hardware upgrade

Following the hardware upgrade at GB3MCB from Cornwall IO70OJ on 144.469MHz, I had a look at the signal.  I make the tropo direct signal to be on 144.469108MHz at present.  Amazing amount of aircraft scatter on the signal, with multiple planes at a time.  Rate of change of Doppler shift has a definite dominant slope, with a few much steeper ones where the plane is closer to the direct line of sight. Range is 458km over a very obstructed path.

Recording here

This is the theoretical doppler shift and distance from centre line of a plane crossing the midpoint  of a 458km path at 90 degrees doing 417 knots

Strange data mode on 144.3743MHz

I am seeing variable length transmissions in an as-yet unidentified data mode coming from due south of IO93NR08. The transmissions are centred on 144.3743MHz and last from a few hundred milliseconds to about a minute, with varying gaps. The modulation starts with a 200ms burst of what looks like two tones about 50Hz apart, then the main transmission looks like a symmetrical Gaussian shape, around 6kHz wide at -15dB from the peak. It is only about 20dB over noise here, but it appears to be a fair distance away as it shows a lot of aircraft flutter, and the zero beat is when there is a plane at around 190 degrees from me. It sounds like noise on SSB/FM/AM. Direction includes Finningley/Robin Hood, Leicester, Oxford and Southampton.

Anyone else hear this? It is pretty regular, but only a problem when trying to work EA/CT on MS.

Frequency shown is the 14MHz IF of my transverter, in USB mode.

This is the audio from SpecLab, showing the pip at start and end circled in red