(meteorobs) Possible alternate meteor monitoring frequencies

[Paul Goelz]

At 10:33 PM 1/16/2013, you wrote:
>For the benefit of a beginner such as myself, could you please
>elaborate on how to recognize airplane tracks?

Sure.  They look a very stretched out "S".

When an airplane sufficiently large to enhance the signal passes 
between the receiver and the transmitter, it produces a Doppler 
shifted return, the same as a meteor.  Like a meteor return, the 
Doppler shift varies with the relative speed of the airplane vs. the 
transmitter and receiver.  However, unlike a meteor, the Doppler 
shift changes the frequency of the return much slower.... over a 
period of minutes (usually) instead of milliseconds.

What you see depends on the scrolling speed of your spectrograph 
display.  If your display is scrolling such that you only have a 
minute or two per screen, an airplane return may be seen as a line 
separate from the actual carrier frequency that moves from low to 
high or vice versa, but not much in any given screenfull.  If your 
spectrograph is scrolling such that you have more than 5-10 minutes 
per screenfull, the airplane returns will be much more 
obvious.  Typically, they will have a mild "S" shape.  The rate of 
change and offset from the actual carrier frequency will depend on 
the path of the airplane.

On 55.240MHz (very strong), I typically see anywhere from 1 to 15 
airplane tracks at any given time.  On 55.260MHz (weaker), I see 
between zero and 5.

Paul

Paul Goelz
pgoelz at comcast.net
Rochester Hills, MI
www.pgoelz.com