[evlatests] A bit more on VOIP RFI.

[vdhawan at aoc.nrao.edu]

More on the VOIP RFI test:

The cross correlation data (much more sensitive than the total-power)
show that the phone signals leak into almost every other antenna.

Anten 22, the closest south of 6, shows the strongest signal, 50-70 dB
down from antenna 6 at different frequencies, (e.g. -190dBm at
1300MHz.)

Antenna 11, just north of 6, shows little, over 100 dB down.  The
leakage appears almost random with distance from ant 6.  Many antennas
are about 80-90 dB down from 6, at 1300MHz. A few, not the farthest,
show nothing. The array was tracking Santa at the north pole, so
fringe winding should not be affecting the RFI. My guess is that the
leakage is very frequency and direction dependent.

In any case, shielding that cleans up the autocorrelations
(i.e. suppresses leakage from an antenna's equipment into its own
receivers) is more than adequate for the cross-power spectra.

V.