4 ms·

This is very interesting. I just have one minor nitpick. Broadcom did not buy Avago, Avago bought Broadcom. They then changed their name to broadcom as it was m

This is very interesting. I just have one minor nitpick. Broadcom did not buy Avago, Avago bought Broadcom. They then changed their name to broadcom as it was more recognizable in the industry (while keeping their old stock ticker AVGO as that was more recognizable in the financial industry). This is entirely a tangent but the rise of Avago from a minor second rate spin off from a spinoff from HP to one of the biggest and most profitable companies of the world (and one that is many times the size of current HP), is one of the most unusual mostly untold stories of the modern business world. It is a story of success (by Avago and Broadcom engineers and management) and incredible incompetence (by hp management that let them go for a pittance).

jjoonathan 2y ago
Oh wow, I was just transplanting some TC702 amplifiers to save the doubler in an old 50GHz HP signal generator... would that have been designed by these guys back when they were part of HP? https://www.keysight.com/us/en/assets/7018-04165/application-notes/5991-3545.pdf https://www.keysight.com/us/en/assets/7018-04165/application... EDIT: that's registration-walled, but this HP Journal article isn't. https://archive.org/details/Hewlett-Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard https://archive.org/details/Hewlett-Packard_Journal_Vol._42_... The amplifiers in question are blue-colored in the background, and the doubler that uses them is the spiritual successor to the rear-most golden module. EDIT2: yep, the timeline lines up. The HP journals with these amplifiers were early 90s, and "This division became part of Agilent Technologies when HP spun off its test and measurement business in 1999. Later, in 2005, Agilent spun off its semiconductor products group, which became Avago Technologies. "
- CamperBob2 2y ago
  83650? I've heard those output amps are very unreliable. Been lucky so far with the one in my 8510C rig.
  - jjoonathan 2y ago
    They've treated me fine -- the broken one I bought that way. YTOs have given me trouble, though. EDIT: obligatory, pictures https://photos.app.goo.gl/KwvnMGm5GyvnmgE58 https://photos.app.goo.gl/KwvnMGm5GyvnmgE58
  - james_a_craig 2y ago
    One of the few places you run into fellow 8510C users. How stable do you find your calibration on the 50GHz 83650 setup? My 20GHz one with the 8341B is very, very, very drifty for the first couple of hours after powerup (i.e. a good load goes from -60dB to about -15dB half an hour after calibration), but I'm not sure whether it's normal or something up.
    - CamperBob2 2y ago
      That doesn't sound right at all. I mostly use mine as a TDR (50 GHz with 83651B) but I can generally reload saved calibrations from months ago, less than 5 minutes after a cold start, and still see < 50 dB return loss through 20 GHz if I look at the same load. I'd go through the receiver channel tests in the manual and try to isolate the problem to the test set or IF box. Does S21 drift as well?
      - jjoonathan 2y ago
        Yes, I'd expect better (though maybe not necessarily 50dB+). Troubleshooting: 1. First suspect is always a bad calibration -- they tend to be unstable in addition to incorrect, but if you have anything with known(-ish) S parameters you can check for correctness too. 2. Second step is to put it in TDR mode and watch to see where the TDR changes. That's where your problem is. 3. A trip through the test set with a torque wrench is a good way to not just check the connections but also calibrate your intuition about the couplers/mixers, which should help interpret #2. You can loosen connectors in sequence and watch them spike on TDR to zero in on the actual problem. As it happens, I was comparing my 8510C + 8517B to a FieldFox recently and I took some drift measurements, although those were on a short rather than a load. The 8510C blew the FieldFox out of the water, lol. Given the TDR, this might be because the standard itself was temperature sensitive and the FieldFox ports are piping hot, but still. https://jjoonathan.github.io/plot_drift.html https://jjoonathan.github.io/plot_drift.html In case they are useful, here are a bunch of different standards measured by the two instruments. https://github.com/jjoonathan/cal-std-8510-fieldfox/blob/main/quick_check.ipynb https://github.com/jjoonathan/cal-std-8510-fieldfox/blob/mai... EDIT: Also worth mentioning, I recently upstreamed my nice 8510C driver into scikit-rf! https://scikit-rf.readthedocs.io/en/latest/api/vi/generated/skrf.vi.vna.hp.HP8510C.html#skrf.vi.vna.hp.HP8510C https://scikit-rf.readthedocs.io/en/latest/api/vi/generated/...
salvagedcircuit 2y ago
Thanks! You sir are correct. I must have been rambling too much on a side tangent. I'll fix this shortly. Optical encoders are most excellent.

jjoonathan 2y ago

Oh wow, I was just transplanting some TC702 amplifiers to save the doubler in an old 50GHz HP signal generator... would that have been designed by these guys back when they were part of HP? https://www.keysight.com/us/en/assets/7018-04165/application-notes/5991-3545.pdf https://www.keysight.com/us/en/assets/7018-04165/application... EDIT: that's registration-walled, but this HP Journal article isn't. https://archive.org/details/Hewlett-Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard https://archive.org/details/Hewlett-Packard_Journal_Vol._42_... The amplifiers in question are blue-colored in the background, and the doubler that uses them is the spiritual successor to the rear-most golden module. EDIT2: yep, the timeline lines up. The HP journals with these amplifiers were early 90s, and "This division became part of Agilent Technologies when HP spun off its test and measurement business in 1999. Later, in 2005, Agilent spun off its semiconductor products group, which became Avago Technologies. "

CamperBob2 2y ago
83650? I've heard those output amps are very unreliable. Been lucky so far with the one in my 8510C rig.
- jjoonathan 2y ago
  They've treated me fine -- the broken one I bought that way. YTOs have given me trouble, though. EDIT: obligatory, pictures https://photos.app.goo.gl/KwvnMGm5GyvnmgE58 https://photos.app.goo.gl/KwvnMGm5GyvnmgE58
- james_a_craig 2y ago
  One of the few places you run into fellow 8510C users. How stable do you find your calibration on the 50GHz 83650 setup? My 20GHz one with the 8341B is very, very, very drifty for the first couple of hours after powerup (i.e. a good load goes from -60dB to about -15dB half an hour after calibration), but I'm not sure whether it's normal or something up.
  - CamperBob2 2y ago
    That doesn't sound right at all. I mostly use mine as a TDR (50 GHz with 83651B) but I can generally reload saved calibrations from months ago, less than 5 minutes after a cold start, and still see < 50 dB return loss through 20 GHz if I look at the same load. I'd go through the receiver channel tests in the manual and try to isolate the problem to the test set or IF box. Does S21 drift as well?
    - jjoonathan 2y ago
      Yes, I'd expect better (though maybe not necessarily 50dB+). Troubleshooting: 1. First suspect is always a bad calibration -- they tend to be unstable in addition to incorrect, but if you have anything with known(-ish) S parameters you can check for correctness too. 2. Second step is to put it in TDR mode and watch to see where the TDR changes. That's where your problem is. 3. A trip through the test set with a torque wrench is a good way to not just check the connections but also calibrate your intuition about the couplers/mixers, which should help interpret #2. You can loosen connectors in sequence and watch them spike on TDR to zero in on the actual problem. As it happens, I was comparing my 8510C + 8517B to a FieldFox recently and I took some drift measurements, although those were on a short rather than a load. The 8510C blew the FieldFox out of the water, lol. Given the TDR, this might be because the standard itself was temperature sensitive and the FieldFox ports are piping hot, but still. https://jjoonathan.github.io/plot_drift.html https://jjoonathan.github.io/plot_drift.html In case they are useful, here are a bunch of different standards measured by the two instruments. https://github.com/jjoonathan/cal-std-8510-fieldfox/blob/main/quick_check.ipynb https://github.com/jjoonathan/cal-std-8510-fieldfox/blob/mai... EDIT: Also worth mentioning, I recently upstreamed my nice 8510C driver into scikit-rf! https://scikit-rf.readthedocs.io/en/latest/api/vi/generated/skrf.vi.vna.hp.HP8510C.html#skrf.vi.vna.hp.HP8510C https://scikit-rf.readthedocs.io/en/latest/api/vi/generated/...

salvagedcircuit 2y ago

Thanks! You sir are correct. I must have been rambling too much on a side tangent. I'll fix this shortly. Optical encoders are most excellent.