Looking for help with an HP 8554B spectrum analyzer plugin

You might be able to substitute them with 1N5711s. It looks like somebody must have accidently transmitted into this unit. You can find these plug-ins at hamfests in the 50 to 100 dollar range now, but the 5711s might at least get you started.

Pete

These *might* be microwave mixer diodes, like the 1N416D, for example. The thing to look for is noise figure. I have a 1L20 spectrum analyzer plug-in for my Tek scope, from the same era as your SA (but much much cruder). I have never seen your SA, but all I can say is that the first mixer in my 1L20 contains a single diode. Do yours look like this?

thing

Not even remotely. Here's a pic of the assembly, out of the "can:"

They've existed since the 1950s.

The principle was postulated in 1938.

AHHHHH... They're wire-ended.

Go to agilent.com and have a look through their range of Schottky diodes. There's almost bound to be something there.

Unfortunately I already did that, and Agilent's Big Book of Semiconductors doesn't have a listing for it.

Don't take this wrong, but Usenet is kinda my last option. Or second last -- I plan on getting a photocopy of the service manual.

Eric

Yes, surface barrier transistors and such used the Schottky effect in those times, but as a collector of some 60s vintage stuff, Schottky diodes are absent in these units. Every other kind of diode, Schockley, tunnel, snap, varactor, back, GaAs, Ge, etc... but not a single Schottky diode. In my 1L20 the 1N5711 performs the same as the 1N416D. So why did they use a complicated to build unit like the 416D if they had had 1N5711-style devices back then? I suppose they must have been used in the 60s because analog samplers with Schottky diodes are certainly in the literature, so maybe they were too new, expensive? Really, I'd like to know.

But as a commercial product, when did Schottky diodes arrive on the market?

thing

Tek

seen

single

top? I'm

I'd like

that they

Testing a microwave mixer diode using an ohmmeter will guarantee that it's dead. They make special low-current meters for testing these animals.

Many possible reasons. One is that their biggest customer (guess who) already had them on inventory.

Old, proven, technology.

Who it was that made them comes into the equation, too. Use an already-approved supplier rather than have to go through the paper chase for a new one. Look at any older Tektronix parts list, for example, and you'll find that some of the biggest names in the industry back then are missing from the supplier code listing. They seemed to like Motorola and RCA best.

Pete,

I'm probably going to have to go this way since other suggestions have appeared to be dead ends for now. Thanks for the suggestion. So... is a '5711 a high-speed Schottkey? (I know, I can look it up, but my connection is very slow right now...)

Thanks,

Eric

The thing

my Tek

seen

single

top? I'm

I'd like

that they

True, I use a 1.5V cheapie analog meter for testing tunnel diodes, but in my limited experience, diodes like the 1N416D can be tested with modern DMM with no damage. But you're right, I should have recommend testing with low current anyways.

Can you get a close up of the numbers? I have a junk box full of odds and ends of HP diodes.

Not soon. The pic was taken by an experienced tech who took a look at it as a favor. I'll have to *gently* get it apart myself or ask him to do so again. He knows his way around RF but was uncomfortable working on this thing; I'm almost scared spitless.

...the joys of microwave...

You don't need to transmit into most older analyzers. Much more than 10dBm will croak some of them. You could do that with some signal generators.

BTDT

Look for devices specced as mixers in the right band at the right power. There should be info somewhere about local oscillator power for this beast.

It's probably only going to be a few dBm, maybe a few tens of dBm.

Eric,

I can confirm that this is/was the right part number. In the '70's a matched pair was ~UKP 150.

You might try something like a pair of BAR28, if you can get them, (Shottky barrier - useful to 10GHz) at UKP 0.5 each IMO they would be worth trying.

Good luck,

-- Roger London UK.

-- snipped-for-privacy@XXbtinternet.com Remove XX for correct email address

I haven't seen them blow out from signal generators, but I have from some of the high output synthesizers that would put out +23dBm. It's too bad that they couldn't make a more robust mixer....................you would figure that they would be using at least a Level 17 mixer.

Pete

My 8554B says "Maximum 10 dBm" on the front in big red letters.

There's probably a reason why they put that on the panel.