[evlatests] More on the Big Pulses

[Dan Mertely]

3100-3300 MHz is allocated to earth resource satellites (active).
You are probably seeing a mapping radar.  If so, it wouldn't be
there all the time.  I'm checking up on which satellite it might
be.  -Mert

On 6/12/2015 9:12 AM, Rick Perley wrote:
>      I've looked a bit more closely at the extraordinary RFI.
>
>      1) The period is within 0.1 seconds of 10.0 seconds.  (i.e., I
> count exactly 60 pulses in 600 seconds).
>
>      2) Every few minutes, a pulse is missing.
>
>      3) My earlier estimate of the pulse duration was incorrect. It's
> actually 1 second, or less.  The earlier estimate did not take into
> account the sidelobes of the radiating antenna.  (With a little work, I
> could figure this out -- but I doubt it's worth the effort ...)
>
>      4) The pulse peak power is 10 to 20 times the total power in the
> spectral window -- so ~ 6000 Jy if it came in through the main beam, and
> was distributed uniformly over 128 MHz.  In fact, it's in a single
> channel (so 64X stronger), and likely comes in through a zero dBi
> sidelobe -- so ~ 10^5 stronger than that.  That's a big number.
>
>      4) Attached is a short plot, showing the total power (PSum) in the
> first four IFs, for a short period of time.  It gives a nice lesson on
> the effect of such power over the entire IF.  The two pulses (the
> stronger at 3250 MHz in SPW#3, the weaker at 3206 MHz in SPW#2) are seen
> in the middle two panels.  In the top and bottom panels, the 'pulses'
> are seen as negative -- this is due to compression, presumably in the
> analog electronics, likely the T304.
>
>      5) The pulses are seen with equal strength on all antennas, and
> equally throughout the 1.6 hour duration of the observation.  The former
> rules out a local origin -- the distance of the emitter is many times
> the scale of the array (B-configuration, so of order 100 km or more).
> The latter makes it hard to believe the origin is airborne.  (But I do
> note that the pulse strength varies over a factor ~ 2 over the 1.6 hour
> duration).
>
>      So this sure looks like a radar signal.  Does anybody run a radar
> on top of one of the local mountains, which they were testing this day?
> (May 5th, around noon).
>
>
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