[evlatests] RFI at L-band

[Dan Mertely]

Coincidently, I was out of the office for the past week.

1381 MHz is the center frequency for the GPS L3 (NUDET)
downlink.  It is normally fairly weak, and very transient.
I had the W8 RFI monitor set to P-band while I was gone,
so I was not able to capture this RFI event.  However, prior
to leaving last Wednesday, the W8 monitor was set to
1375 - 1385 MHz, monitoring a *scheduled* GPS L3 event.
The monitor plot for Wednesday 16 January is attached.
It shows very strong, broad RFI in the 1378 - 1385+ MHz
frequency range.  Signal levels are around 30 dB over the
F103 L-band, 35 K noise level, so it sounds a lot like what
Rick saw on 28 & 29 January.  When I saw the plot (before
I left), I assumed it was related to the scheduled SV57
testing, although it didn't have the characteristics of
previous transmissions.

I will move the W8 RFI monitor to cover L-band again & see
if we can catch the problem while it is happening over the
next few days.  Meanwhile, I would appreciate any additional
info.

PS:  We do not allow microwave ovens anywhere on the Site
and if we did, they operate in the 2400 - 2480 MHz ISM band.

-Mert


Rick Perley wrote:
>     We tried to reproduce the 'failure to tune' problem this morning, 
> but find we are being completely wiped out by enormous RFI:  from 
> Walter's FFT spectrum scanner, the interferer is centered at 1484.8 MHz, 
> with a width of nearly 20 MHz, and a peak spectral density 100 dB above 
> the noise floor! 
> 
>     Anybody have any idea where this is coming from? 
> _______________________________________________
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