Digital " Ladders " captured and demodulated

Following the post at the links : 

http://air-radiorama.blogspot.it/2017/02/quasi-risolto-il-mistero-delle-scalette.html

http://air-radiorama.blogspot.it/2016/08/parzialmente-risolto-il-mistero-delle.html

http://air-radiorama.blogspot.it/2017/02/ancora-novita-sulle-scalette-ladders-in.html

This is the video of the digital ladder that I called "ghost" .

It pops out in two parts of the spectrum .

In the second part ( at 10.7 MHz ) I have demodulated it in baseband with a wideband spectrum with components spaced 50 and 200 Hz .

Some second after the end of receiving this ladder you can see and listen the transit of a typical continuous sweeping ionosonde .

The BW of the modulated signal was evaluated graphically to be around 20kHz as in the following images and the modulation time to be around 0.6 s .

Here you can find one authoritative comment about :

Claudio:

The full-resolution images make it possible to read the axis labels, so the vertical marks are approx 10 secs. The chirpsounder in the ghost10k image (above the irregular-step broadband trace) is therefore sweeping 500kHz in

10 secs, which makes it a 50kHz sounder.

Digisondes step at a uniform rate. The DPS4D steps 25kHz every 640msec.  So the traces on the ghost10k image is not a Digisonde since the steps are

irregular in both the time and frequency axes.   I don't see any traces in

these "ladder" images which could be a Digisonde.  There is more information about the Digisondes on the UMLCAR and DIGISONDE websites.

My guess is that the irregular-step signals are path sounders. They emit a burst of MFSK on many channels in sequence to keep track of which frequencies are open for the path they are using.  It's not surprising that they follow a sequence up the spectrum.

73

Peter G3PLX