Hello Gerald,
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Interesting discussion, and thank you for this work. It's indeed a shame that such nice analyzers as the HP8560/90 series has this common issue. I have an HP-8561E with a dead YIG.
I looked at your comparison table, and I think there is a mistake in the main coil tuning sensitivity.
From an old datasheet of the HP YIG that someone posted here, the main coil sensitivity is 22/23/24 mA/GHz, not MHz/mA. So converting to MHz/mA (the inverse), this would make the sensitivity 40.8/43.5/45.5 MHz/mA. An even bigger difference from the Teledyne YIG.
I also considered various replacement YIGs, and I bought an Avantek one on eBay just to play around with, but that one has a sensitivity of 19.5MHz/mA and a coil resistance of about 10 ohm, so also a bad fit.
Also, I think what makes replacement difficult is the way that the HP8560 series do the sweep. From the manual, it says that a 'lock and roll' method is used for sweeping that involves an open loop sweep. For sweeps larger than 20 MHz, the main coil YTO is swept open loop. For sweeps between 2 and 20 MHz, the FM coil is swept open loop, and for sweeps smaller then 2 MHz, the Fractional-N PLL is swept in lock. In my understanding, this means that the coil sensitivities (Main and FM) must appear to the analyzer as being the same as the original YIG.?
So far, I have been weary of spending 1,000 USD for a replacement YIG, so I am happy to hear any other suggestions you folks may have in this thread.
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BR?
Peter OZ1CPQ
