| Products > Test Equipment |
| HP 8566B - What to look for? |
| << < (11/13) > >> |
| W4PJB:
Great info, thank you! That's a very generous offer to test your own 8566, it's much appreciated. |
| G0HZU:
--- Quote from: W4PJB on June 22, 2024, 10:35:36 pm ---Thanks, and great point about the signal being attenuated twice. I did set the 8566 to 0dB. VNA was -10 dB, as G0HZU suggested. Guess it's not looking too good for Uncle YIG? --- End quote --- It might not be being fed the correct control current for 2.7GHz (or any control current at all) so there still might be a simple fix for this issue... Now is a good time to be cautious and not be too hasty pulling or probing connectors etc. I don't know how fragile some of these modules are or how tolerant they are of misprobing or shorts etc. It's probably best to do as much external testing/diagnostics as possible. Try the 'SHIFT' 'GHz' combination to bring up the DAC control and see if anything changes (even slightly) across the full DAC range. |
| KE5FX:
Here's how mine looks (and you can see the parameters I used for both the 8753 and 8566 if you look closely): Again, while it could be the YIG, you will want to check the coil current before making any assumptions. It is more likely IMO that the preselector driver circuit has a bug. At zero tuning current the YTX will probably not exhibit a meaningful dip anywhere. |
| KE5FX:
Something else to note -- once you do observe an S11 response, you may get a deeper notch if you bump the 8753's point count up to 801. Depending on span, the default 201-point sweep may not have enough resolution to show the full effect. In fact, when making S11 or S21 measurements on a narrowband YTF using a wide VNA span, you can potentially conclude that a good filter is faulty because the notch lies entirely between two points. BTDT :( Also: use 0 Hz span on the 8566. No reason to sweep the filter while you're trying to measure it! |
| G0HZU:
You can also try pressing ‘SHIFT’ ‘PRESEL PEAK’ to restore the factory control of the YIG current. My analyser had some serious holes in the YIG tracking, and pressing the above buttons fixed it. However, your symptoms are a little different. |
| Navigation |
| Message Index |
| Next page |
| Previous page |