polB if1 attenuator failing


    The upstairs if/lo has two sets of attenuators:  rf attens (before the mixer) and if1 attens (after the mixer). These attenuators to 0 to 11 db in 1 db steps.  When testing the sbn receiver on 11dec16, we saw that the attenuator values for polB if1 attens were jumping around. Normally the if1 attenuators are not needed ..
Sbn started needing the if1 attens when the 2355-2360 rfi got very strong.

    On 12dec16 we ran a test to see if the if1 attenuators were working ok.
The setup was;

The plots show the power levels for the various attenuator settings (.ps) (.pdf):


processing : x101/161212/tstif1attn.pro

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