aircraft reflections

this is a very interesting example of an upcoming signal

op: OM5KM - Milan
locator: JN98BG (QRB 137 km, QTF 83° from oe1smc )
date: Tuesday, 2007/08/07 20:35:30
software: WSJT mode: JT6M

if you watch the 6m-band during the season, this is maybe a daily seen situation, but if you look at the spectrum of this signal, you can see the following

btw: i took DL4YHF's Spectrum Lab from Wolfgang Buescher, really a great program.

i assumed, the signals below 1000 Hz drifted, so i zoomed between 950 Hz and 1050 Hz to see details:

and indeed, there are some drifting signals. there are 3 “directions”

  1. the stable qrg of the transmitter
  2. a group of frequencies with little drift
  3. and a group with bigger drift

so what happened ?

the most common opinion is, these are aircraft reflections with doppler effect (or doppler shift). there are 2 groups of frequencies, therefore there must be 2 aircrafts with different distance and different directions.  

tnx to George G4PCI for his opinion and answers.

this is the wave-file produced by WSJT

oe1smc 1/2010

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