[evlatests] RFI, VOIP phones - Summary

[Vivek Dhawan]

After this morning's discussion:

1. The interference from a phone in the vertex room to the
    L-band receiver in the same antenna needs 70-85 dB shielding,
    IF the antenna is doing science observing with the phone/light on.

2. The highest signal in any neighboring antenna indicates that
    20dB shielding suffices to allow that antenna to continue
    in the array. (Based on this one measurement.)

3. The shielding levels above are predicated on the ITU harmful
    levels for single-dish use. Since the RFI test was done tracking
    the North pole, I assume the attenuation from fringe winding was
    not happening during the test.

    EVLA memo #49 by Perley gives the result of imaging simulations,
    showing that a minimum of 15dB attenuation of interference occurrs
    over the array, for ANY fringe rate. Assuming this result holds for
    narrow-band signals, then modest shielding of the NEC VOIP
    phones would allow their use on an antenna not in the array, while
    the rest of the array continued observing.

    I suggest an eventual target of 20 dB shielding.

4. The next test is to look for the synthsizer comb on an EVLA antenna
    (Dec 14th).

5. After that, another test of the phone (or test tones) is probably
    needed on an EVLA antenna - the above test was on VLA antenna #6.

    The L-band EVLA feeds have been measured (by Mertely?) to leak
    through the walls, with the top covered.

Vivek.