04.18
About a month ago, I managed to score an HP 8444A Tracking generator to go with my HP spectrum analyzers. A TG is a fantastic tool to sweep filters and circuits to get a feel for the response curves of said circuits.
The 8444A was initially built to go with earlier generation of SA than the 8558 and 8565 SAs that I have. In order to work with newer SAs that don’t have a 3rd LO output you either need an 8444A with option 59 or you need to feed it with 500Mhz from a frequency generator.
I’ve been using mine with 500mhz coming from an 8640B @ 0 dBm. Somewhere in the last 20 hours I know I managed to bump that up to 20 dBm for at least a few sec. This may or may not be related to my current problem.
The display used to be a nice relatively flat sweep from 0 up through ~1.4Ghz, where it rolled off to zero.
Late last night, I saw the curve had a lot of ripple/noise in it and a notch in it at about 74Mhz. What have I done!?!
So tonight I’ll break out the 8558 spectrum analyzer and see if the artifact is a product of the 8444A or of the 8565A.
Update: 4/25/11
Nope, it wasn’t blown up. Thanks to the folks on the hp-agilent-test-equipment mailing list, I traced the problem down to a bad cable.
In the process, I learned a great deal and made some good progress on the 500mhz oscillator, option 059 replacement.
I built an “option 059” oscillator for my (059-less) 8444. Works great. Let me know if you want the details. ExpressPCB board already designed. Uses a Mini-Circuits VCO and I temp compensated it.