[evlatests] RFI-free 64MHz subbands within L-band

[Dan Mertely]

One minor concern for the 1st 2 "clean" sub-bands
listed:  Depending on the visibility of GPS and
GLONASS satellites, these 2 sub-bands could look a
lot worse.  The GPS satellites transmit the L2
(military precision) code continuously on 1227.6 MHz,
+/- 20 MHz, and the GLONASS satellites transmit their
equivalent military data in 13 narrow channels from
1242.9375 MHz to 1248.625 MHz.

These transmissions are seen fairly clearly on the
(relatively insensitive) W8 monitor around 30% of the
time.  I would think that the VLA would see them at a
much higher level, far more frequently.  ... Perhaps you
just "got lucky"?

-Mert


Rick Perley wrote:
>     The availability of a 'RSRO-style' correlator setup enables a more 
> efficient L-band observing capability.  In the past, with only 128 
> MHz-wide subbands available, one needed only a single IF pair -- either 
> AC or BD.   Because of the copious RFI within L-band, the chances that 
> all eight 128-MHz-wide subbands would contain some RFI is very high, 
> leading to degraded values of the switched power, and hence degrading 
> the gain calibration. 
> 
>     With 64 MHz-wide subbands now available, we have a better chance of 
> placing the 16 subbands in places where more of them will be free of RFI 
> for more of the time.  In addition, the doubled spectral resolution (1 
> MHz rather than 2) gives better RFI editing capabilities. 
> 
>     I ran a short test today using 16 64-MHz-wide subbands, spanning 
> L-band, and centered at 1500 MHz.  I observed five sources over one 
> hour.  In that period of time, the SY table values for 7 of the 16 
> subbands were completely clean.  Two more showed clear sign of periodic 
> radar -- the pulses are easy to identify and clean up.  So at least 9 of 
> the subbands look quite good.  Below is a list of the good ones. 
> 
>     1180 -- 1244 MHz
>     1244 -- 1308 (has radar, easy to edit)
>     1308 -- 1372 (has radar, easy to edit)
>     1372 -- 1436
>     1436 -- 1500
>     1756 -- 1820
>     1820 -- 1884
>     1884 -- 1948
>     1948 -- 2012
> 
>    
> _______________________________________________
> evlatests mailing list
> evlatests at listmgr.cv.nrao.edu
> http://listmgr.cv.nrao.edu/mailman/listinfo/evlatests