The ~350 Hz noted in the elog below was traced to an RF modulation of the 11 MHz sideband. This modulation was set up in the Marconi which is currently supplying the 11 MHz local oscillator signal to the RF source. lt was used during the MC length study completed last week by Valera and Ryan. The frequency measured was 322 Hz.
As we do not require this any longer, I have switched off this modulation.
The Demod board with S. No. 022 (being used earlier as REFL11) has been modified. It now has SCLF-65 as its input LP filter on the PD input line and a PQW-2-90 power splitter. The unit functioning okay (I and Q signals are 90 deg apart.
The loss of Q output was traced to a possible loose solder joint and we now have both the I and Q signals after resoldering all components in the vicinity of U7 (Ref Schematic of D990511)
There is a strong oscillation around 350Hz present on I and Q signals of both REFL55_Demod and POY55_Demod. Don't know the source.
We have run out of power splitters to continue with the Demod board modification. We do not currently have an AS11_Demod board. All the others are in place and ready for the I<->Q phase angle measurement.
In summary we now have the following Demod boards in place:
[ REFL11, POY11, REFL55, AS55, POY55, POY22, POY110]_Demod