The RF distribution box has been modified so that it generates two more 55 MHz LO signals.
After the modification I put the box back in place.
Then I checked the MICH and YARM locking quickly as a working test of the distribution box and it is working fine so far.
I will update the diagram of the RF distribution box (#4342) tomorrow.
(Motivation)
Since we newly installed POP55 (#5743) an LO signal was needed for the demodulation.
However the RF distribution box didn't have any extra LO outputs.
Therefore we had to make a modification on the RF distribution box so that we can have a 55MHz LO signal for POP55.
Eventually I made two more 55MHz outputs including one spare.
(Modification)
The box actually had two extra output SMAs which had been just feed-thru connectors on the front panel without any signals going through.
In the box the modules consist of two categories; the 11MHz system and 55MHz system. I modified only a part of the 55MHz system.
The modification was done in this way:
* split two branches of 55MHz into four branches by installing two new power splitters (ZMSC-2-1).
* made and installed some SMA cables whose length were adjusted to be nicely fit in the box.
* readjustment of the RF levels to 0-2 dBm at the outputs by replacing some attenuators.
* checked the signals if all of them were happily coming out or not.
Also I found that the POX11 and POY11 demod boards were connected to the whitening filters in a wrong way.
The I and Q signals were in a wrong order. So I corrected them so that the upper inputs in the whitening filter is always the I signal.
(RF levels on 55MHz LO outputs)
Since the demod board requires a certain level of the RF signal as as LO, the LO signals have to be 0-2 dBm.
Here are the RF level in each 55MHz output after the adjustment of the level.
AS55 = 0.76 dBm
REFL55 = 0.76 dBm
POP55 = 0.79 dBm
spare = 0.83 dBm
Those numbers were measured by an oscilloscope and the oscilloscope was configured to measure the rms with the input impedance matched to 50Ohm.
In the measurement I used the actual input seed 55MHz signal from the RF generation box to drive the distribution box. |