[evlatests] RFI & AM889 on July 23

[Dan Mertely]

Hi Ed.  Yes, there was strong L-band RFI, centered around
14513 MHz from 1455 - 1555 UTC on 20070723.  It had the
characteristics of White Sands Missile Range (WSMR)
airborne telemetry.  They use 1440 - 1460 MHz quite frequently
to transmit position and other data from aircraft running
up and down the valley to the telemetry control area
at WSMR.  They do not notify us of flights.  I see the
RFI on our W8 monitor around 2-3 times a week, always during
the daytime.

If you think it would be useful, I could request special
quiet time from WSMR for your future, pre-scheduled spectral
line observations in that frequency range.

-Mert

Interference Protection Office
VLA


Ed Fomalont wrote:
> AM889 on July 21 and 22 went well except for the usual problems.
> AM889 on July 23 a little less well with a few more problems.  See below.
> 
> 1.4 GHz, 2 IFs, 2 Pols, usual deep integration setup of 7 channels
> 5 hour experiment, 3.3 sec integration
> 
> 26 antennas working.  11 and 25 out
>    July 21  ante 28 out most of run
>    July 22  all 26 antennas okay
>    July 23. something wrong with ante 5 IF 1, R pol.  Junk correlation
>    July 23  14:30 to 16:00 horrendous interference, worst at 1.385 MHz, 
> Pol R.
>                  All data useless (I assume this was external interference)
>    July 23  Bandpass for antenna 13, IF2, L Pol has large amplitude steps
>    July 23  Bandpass for antenna 14, IF1, L Pol has large amplitude steps
> 
> On all three days
>    quack needed for about 15 sec on each scan
>    First experiment scan of 5 minutes was junk, and then EVLA antennas 
> had junk another
>          5 minutes
>    Ante 14 only has anomolous phase drift for second scan of 4 min (on 
> all three days)
>    Last 1 min of data is junk
>    Phase jump on EVLA antennas after switching to X-band pointing check 
> - expected and very repeatable.
> 
> Ed
> 
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