Friday, 18 May 2007

E25: AM or not AM?

A brief "control" transmission from my favorite Enigma, E25, occurred today at 1143z. An OM started calling "785 58 788 45 46 50 52". The transmission was in AM mode.

Next, I'll show you the spectrograms from these transmissions: While recording, I switched to USB and detuned the radio for 1-2 kHz to see if both sidebands are present. Today we had...

The 1000 Hz horizontal line is the carrier, both sidebands present. (Audio)

Yesterday it was another story... LSB-suppressed, a couple of problems during startup, and a brief musical segment just before they QRT. The "control" message was "788 45 46 50 52 58 " also sent at 1143z.

The 2000 Hz line (and a 1000 Hz bit during re-tuning) is the carrier, only USB present. (Audio)

I hope this visual/audio representation was useful. I wonder when E25 operators will settle in a fixed mode and a fixed schedule...

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