Wednesday, December 12, 2018

Test Equipment Status

This is turning into one of my down-the-rabbit-hole adventures.......

This all kinda-sorta started out when we moved here. I didn't pack my signal generator (at all), and it slid around inside the trailer I was pulling, breaking off an input level adjustment knob, and bending the other.

I was pretty sure I could fix it, but I'm glacially slooow doing this (take it apart, see what broke, find the parts, order the parts, etc, etc) kind of work, and I really wanted a newer generator with more features, so I looked around and bought a nice used one which should be here Friday.

But not knowing if my "old" generator still functioned, I set up my frequency counter and Spectrum Analyzer so I could measure the output.

I've been seriously using Spectrum Analyzers since 1982 when I went to work for Hughes Aircraft. They're a very powerful tool for radio work, allowing you to make accurate, repeatable measurements in a fraction of the time it would take using "classical" methods. I understand them pretty well, BUT......I always get things all scrambled up when going between units made by Tektronix, and units made by HP/Agilent. The HP units are very intuitive to use while the Tektronix units are more like your practical for a Master's Thesis. And the controls are not laid out in a logical grouping, and many features I'm used to having are not available on my Tektronix 494 unit. So naturally, when I first powered it up I had forgotten how different it was, and proceeded to get it into a state where it couldn't even see the internal CAL signal.

Hey, I hate this old clunker anyway, so why not go shopping for another unit, and this time buy an HP.

So I did.....

It's an HP 8594E model, and "only" goes to 2.9GHz, but that's plenty for my needs. Has a nice, bright trace....

And in general is very clean.

It's been a "Bench Unit" it's entire life, unlike some of the ones I've dragged around/banged around the ships for Sea Launch!

And even though I paid $40 for shipping, my total was $988, about half of what these go for from a Test Equipment Store.

So anyway....after buying this last night, I went back downstairs to shut things off, and gave the old 494 one last try.

Yep, the damn thing works! Here it is displaying a 100MHz signal from my old generator.

It's drifty for a least an hour after turn-on, but after that it seems stable. The Pilot Induced Problem was that I had the reference level and input attenuator set wrong, essentially making it "deaf" to the signal levels I was trying to monitor.

And the generator only has a 100HZ error at 100MHz......

I'm assuming my counter to be "accurate" as it has the best timebase on-site (one of those nifty HP Ovenized Crystal Oscillators), and it had a current calibration when I bought it some years ago.

I have a known-good Rubidium Frequency Standard with a 10MHz output, so as soon as I get that fired up, along with my HP "GPS Clcock/Timebase", I should be good-to-go for accuracy.

Having any instrument that makes measurements of time or frequency connected to a "Master Timebase" or "Master Clock" keeps them all synchronized, and helps reduce measurement errors.

So at long last, my Radio Lab will have a Tektronix Oscilloscope and an HP Spectrum Analyzer as God and the Chief Radio Engineer have commanded.....

Tonight's project is to finish up the Drake MS-4/AC4 speaker/power supply. This will get the bench cleaned up so I can make some BNC patch cables in 3~6' lengths.

Having fancy test gear is nice, but without patch cables to hook it all together, you can't do much with it. Making accessories like patch cables is a good way to save a few $$, too. I'd rather buy my connectors "By The Dozen" and a spool of cable than pay $12~$25 EACH for a cable. My cost of parts is probably less than $5, so that adds up on 10 cables. It's mindless radio 'grunt work' and not as glamorous as tuning up transmitters or bringing a dead receiver back to life, but it's relaxing and keeps me out of bars.......


  1. It's always nice getting your hands on the right tools. Sure, you can 'save' money with that Horrible Freight tool, but it's worth it to pay more for something that actually works right.

    Good job on finding that HP and discovering your baby lives.

  2. I'm happy (but $750 poorer) that my old Systron-Donner still works, but the Tektronix being "usable" is a hoot.

    I forgot how much I hated that thing until I fired it up to use it.

    And as my daddy taught me, "You might pay more for the right tool, but you only buy it ONCE".

  3. drjim, I know nothing but that looks like an upgrade! Good to know you have SIGINT in hand.

    1. More like maintenance depot stuff, but thanks for vote of confidence!


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