20110608

It seems like I have lots of things to do, but many of them depend on other things and as a result I end up doing nothing! Here's what I should be doing, in order:

• Test IF sampling with my ADC. I suspect that this will not work well with my current front-end amplifier design, but it's worth a shot. The LTC demo board has a 5-140MHz front end, which would be perfect for this, but I don't have the PStache data acquisition board with me here - could have it posted over or get someone in Canberra to test it.
  • Because the design is decimating the signal, I have to capture the raw output (rxd[15:2]) and capture this with ChipScope Pro. Currently re-generating the bitfile - will test when it's done.
  • Signal generator is broken. Disassemble. May be a problem in the CPU module. Will continue to read service manual.
  • Do a frequency sweep with signal generator. Get some data dumps and look at them in CSP, then possibly Matlab if it warrants further investigation.
  • If attenuation is high, examine the THS4521 data sheet to see if there's anything obvious I can do.
  • I can try connecting my tapped 1:1 transformer directly to the ADC inputs by removing some resistors, though I have no idea what the frequency response of my transformer is like - probably bad! Worth a try.
• Find out what's happening with the front-end BPF.
• Revisit four channel receiver design - I can start the schematic and add the DDS. Do some research on suitable GPS modules with 1PPS output, find where I put the GPS disciplined oscillator paper.
• Consider doing some field tests with the existing receiver.
  • It's fragile and not very portable at the moment!
  • I can use two Si570 modules as LOs, but the output signal levels may be a bit too high - test this. Actually, it might be pretty close after the splitters/amplifier.
  • Can read registers from Si570s, but can't adjust frequency! Try XP machine instead of VM. No, seems like a fault on that board. Investigate.

Buy some stuff

• Await micro HDMI cable. Source some HDMI connectors.
• It'd be good to get some inline BNC attenuators and 50 Ohm terminators (from Clarke and Severn?)
  • HAT-10+ - $9.95, 10dB
  • Can't see inline terminators. Quick look at Digikey shows that they're out of stock and $40.
  • Write to Mini-Circuits to ask - don't sell them.
• Go to Big W. Done.