Carriage House 30 MHz -> 260 MHz Cabling Notes
Aim: to upconvert CH signal (which comes down at 30 MHz IF after a single
mix from 430 MHz RF) to 260 MHz for input to the correlator during X102
calibration observations. This procedure will also be useful to pulsar
observers wishing to upconvert the IF for input to the WAPP.
- On Rack 3, the receiver LO driver should be set to internal (to ensure 430->30 MHz mix takes place)
- Make sure the knobs on rack 7-2 are set to (from left to right) CRR/LRR1 --- INPUT ON --- INPUT ON --- CRR/LRR2
- On Rack 9, select ANT LONG RANGE
- Get the 30-MHz IF signal from outputs of 7-2 into IF distribution amplifiers 7-3 (left channel) and 7-4 (right channel). At this point, it is a good idea to feed the 30 MHz signal into the spectrum analyser to make sure that you can see the pass-band!
- Set the power meter in rack 5-3 to measure from the front panel via the vw% command: vw% if2 "if2_pwrm fp" now feed in the outputs from the distn amps 7-2 and 7-3 into the left and right inputs of the power meter in rack 5-3 and adjust the attenuation until you read -30 dBm in both channels. N.B. Because there is a 20 dB pad in front of this meter, the power coming out of 7-2 and 7-3 is actually at -10 dBm --- this is the desired level we need for the next stage.
- Feed the 30-MHz outputs from 7-3 and 7-4 into the 30-260 MHz upconverter located in 3-11 (for a sanity check, you'll see that the inputs to 3-11 are labelled to remind you that -10 dBm input signals are required)
- Set the synthesizer (3-8) to 230 MHz and feed its OUTPUT to LO-IN 230 MHz on the upconverter unit (3-11). Again, as a sanity check, the LO should be showing -13 dBm for this signal, which is the required power level.
- Feed the 260-MHz outputs of 3-11 into the attenuators in rack 7-14. N.B. use the pair of attenuators which have 10 dB steps here, since you're going to need to attenuate this signal to get it within range for the correlator.
- Feed the outputs of the attenuators 7-14 into the 260-MHz IF distribution amplifiers 6-15 (left channel) and 6-16 (right channel)
- Feed 3 outputs from 6-15 into external input #7 of racks 4-12, 4-13 and 4-14. Likewise for the 3 outputs from 6-16 -> ext input #7 of 6-11, 6-12 and 6-13
- Connect the Cal monitor (rack 5-11) into cal 1 and cal 2 of rack 9-2 using a T-junction to split the signal into the cal inputs of 9-2.
- Select the Cal temperatures for the left and right channels from the dials in rack 8-1. We are using 31 K (left) and 36 K (right)
- Step back and admire the cabling that you've just done before double checking it at each step.
- Go to the source and do: vw% coradjpwr and iteratively add attenuation into 7-14 until the correlator attenuators are set ~7 and the resulting power ratios are around 1.0
This document was generated by Duncan Lorimer on December 3, 2000