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”
- the stable qrg of the transmitter
- a group of frequencies with little drift
- 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