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.
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
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
Machining and Ham Radio experimentation from VLF to SHF