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Re: (meteorobs) Doppler effect heard on FM

At 14:44 2001/01/18 +1100, you wrote:
>Again I heard the doppler whistle on 93.3 FM this morning 18/1/01. It tended 
>to be quite faint & did not create much of a train (10 secs)

Assume that you're using a communications receiver and beating its local
oscillator against the incoming signal (in SSB or CW mode position).
Otherwise, there would be nothing for the incoming signal to beat against
and thus no way to detect (by ear) the presence of Doppler shift.

The higher the RF frequency in use, the more pronounced the Doppler effect.
On 144 MHz, Doppler is much more common some days than other days.
*Probably* because on those days many of the "sporadics" or "non-shower"
meteors are actually remnants of some old shower, thus having a common
radiant & path, etc.  I may go for several weeks (of one 30-minute schedule
per day) and hear no noticable Doppler, then get 3 or 4 on the next day.
Most commonly the  Doppler is heard on ½-second or so underdense bursts.
On an overdense burst, Doppler (enough shift to be noticed) normally will
be heard only at the very beginning of the reflection; thus from the
reflection of the rapidly-moving head region.

I have saved to disk several hundred interesting short pings.  I'll see if
I can find a couple with good Doppler and add them to the Sounds section of
my HSCW Web site.  Trouble is, they're only identified by date and station
- have to listen to each one or read the bundled information to find those
with Doppler shift, so not a quick job.  But could probably find a couple
if anybody is interested.  (There is one screen shot example of the extreme
"picket fence" flutter sometimes heard on overdense bursts, but don't
recall having put any Doppler examples there).

73, Shelby, W8WN

Shelby Ennis, W8WN - EM77bq - KY
                w8wn@arrldot net
              w8wn@amsat.org
   Web - http://www.qsldot net/w8wn/  
                       <><


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