Hello Craig,
??? Since I noticed that you were one of the rare persons to still know about The HP TDR equipment 1817A, I just give you the end of the story : By chance, I manage to get two genuine sampling diodes in good condition from an old equipment, and my TDR is now working again. But I recognize that designing new sampling assemblies from modern beam lead microwave diodes is the only long term way to carry on with this equipment. As a matter of fact, digital scopes from Le Croy or Tektro? offer the same performance (even better) without sampling, but they are far above my financial means. Recently, a small start-up US company offers a sampling box for P.C., giving good performances (up to 12 GHz) at a reasonable price, and their schematics is available. I might try to build one, but right now, my old HP stuff in convieneient for my use, as long as I protect the sampling diodes from overvoltages (+-1.5 V) !
?? Anyway, thaks for your help !
????????????? Jean-claude
JCB_SFR