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What Loran Signals Look Like

I was wondering what Loran signals look like. I took a few shots with the Tek 494P spectrum analyzer using my low band antenna (a 20m piece of wire slopping from about 50 feet down to 30 feet).

I am not very far from a powerful Loran station, Malone, FL LORAN, about 30 miles due south of Dothan, AL.

They run 800kW into a 700 foot monopole array. For more info see www.uscg.mil/d8/lorstamalone/default.asp

The signals are loud, in spite of the fact that my antenna is way too short and too low to be effective at that frequency. A tuned loop would probably work much better.

The first 3 pictures were taken with the analyzer in Peak-Hold mode for about one minute. The Loran signal being pulsed, a single sweep does not reveal the actual spectrum.

Screen shots courtesy of John Miles' 7470 emulator software with a Prologix GPIB-USB controller plugged in the spectrum analyzer.

This is a narrow Resolution Bandwidth (1 kHz) measurement. The RBW is too narrow to properly show the occupied spectrum.

This is a shot at wider RBW (10 kHz)

This is a shot with a 10kHz/div span and 10 kHz RBW.

This picture is in the time domain, using the spectrum analyzer as an oscilloscope (5mS/div)
You can clearly see the pulses, the different amplitudes come from different stations.

This picture is in the time domain also with a faster sweep (2mS/div)

 


Links:

  • John Miles' GPIB Toolkit, www.ke5fx.com
  • Prologix, prologix.googlepages.com