24 November 2015

evidence of a 'Doppler shift' in a parallel signal

some days ago me and KarapuZ were checking if a 188-110 App.B signal had the usual preamble rather than the extended one, KarapuZ has noticed a  slight shift in the detection of carrier and harmonics of the upper channel (Pic. 1), more likely the shift is the result of the Doppler effect due to a "moving" transmitter. The Doppler shift is also clearly visible by just highlighting the doppler-tone (Pic. 2). Asking more exeperienced people, they argue that the object motion is accelerated at rate of 3 m/(sec*sec): maybe a jeep or a ship.
Whith regard to the preamble, since the measured values, that signal has the "normal" 14 + 8 signal element periods preamble (Pic.3) as reported at "B.5.4.1 Preamble", page 81 of MIL-STD 188-110C doument.

Pic. 1
Pic. 2
Pic. 3

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