S-parameter test sets

Forgot to mention pros and cons :

Obviously, you want to be matched to your target device, although it is possible to do the transform (because you know the mismatch).

In general, 50/100 ohms is the most prevalent impedance for high speed stuff (where S parameters become very important), so 50 is probably a good choice, unless you have some particular equipment in mind that is something else.

The tradeoff in systems for each impedance is really a balance between drive (higher impedance, longer distances, generally) and lower noise (lower impedance, lower noise).

Cheers

PeteS

Most common would be 50. In the CATV biz I suppose it would be 75.

Unless you're in the CATV (video) biz, there is no pro for 75.

Wow, how did you acquire one of these? Before my retirement I had one in "my" (Hughes) lab. I seldom used the s-parameter TS, since I also had available an HP8510C. If I remember correctly (risky propostion these days), the TS was not a true reversing one where all four parameters could me measured with one connection. There certainly wasn't enough trace memory for all four parameters, maybe that was the limitation. Anyway IIRC you will need software to make full two-port measurements.

Mine wound up being mostly used to characterize quartz crystals. I wrote software (HP-Basic) that my friends tell me is still cranking away. I made extensive use of the trace math capability of the analyzer to limit the workload of the computer. (HP-9836 fully loaded with a whopping 1M of RAM!)

Today in retirement, I'm content with my N2PK network analyzer.

[...]

Terry,

Are you talking about a different unit? Here's the description for n2pk:

" capable of both transmission and reflection measurements from 0.05 to

60 MHz, with about 0.035 Hz frequency resolution and over 110 dB of dynamic range. Its transmission measurement capabilities include gain/loss magnitude, phase, and group delay. Its reflection measurement capabilities include complex impedance & admittance, complex reflection coefficient, VSWR, and return loss."

This is a neat system - fits on a 2.5" x 3.8" pcb, so it can't be that difficult to build.

For low frequency work, it might be possible to extend the low frequency limit by reducing the crystal frequency. However, oscillator jitter is important. Read his article "Testing of the Fox JITO-2 Oscillator as the N2PK VNA Master Oscillator":

Mike Monett

[...]

Yes, 50Hz might be slow. It might be worth looking at variable sampling time. Longer sample time for low frequency data points, then speed it up as the frequency gets higher.

The thing that appeals to me with this approach is you have complete control over your destiny. If anything breaks, you can always fix it, or redesign it as the technology improves.

Old test equipment might be inexpensive, but eventually you can't find parts needed to repair it anymore. And it somehow finds a way to fail just when you need it the most.

I just gave away a complete TEK 7854 system with many plugins that gave excellent service for many years. It developed a fault in the display system that I couldn't fix, and couldn't find a replacement card. Some of the plugins were starting to go, so the handwriting was on the wall.

Mike Monett

what is the most common impedance used with S-parameter test sets - 50 or 75 Ohms? my guess would be 50 Ohms, based on no knowledge whatsoever.

what would be the pros and cons of one vs the other?

I am looking at buying one for my 200MHz HP3577 network analyser

Cheers Terry

thats kind of what I thought.

I saved for a while, then spent $2000.

The manuals havent arrived yet, but I am going to have to figure out how to drive this puppy in some detail. Any knowledge you would like to impart will be gratefully received (and archived).

yeah, thats pretty neat. I thought about making one, but I want to do control loop analysis (among other things) and so need phase too, but not as much bandwidth - but 200MHz is still pretty useful :)

Cheers Terry

oops, yes I was. but I had seen the n2pk before.

nope. hard to beat opening a box though.

its great stuff, I read and archived it a while back.

I really need to get below 50Hz for power supplies - eg PFC loops tend to have closed loop bandwidths smaller than line frequency.

Cheers Terry

Hello Terry,

That is a very good price I think. It is a nice analyzer. The only downside is that it won't function as a spectrum analyzer.

Regards, Joerg

[snip]

I do have something in my storage building. Not actual instrument manuals, but some app note stuff. I'll dig it out and see if I can scan it for you. I have only a 28.8K dial-up tho and big files are a pain to send. Maybe I can break it into pieces.

I'll get back to you.

Wes

Terry,

This should get you started:

Wes

thanks,

I've got to run to some appointments but I'll try to get some more of the doc posted later.

Wes

ps. I see I need to update my email address on my site. Direct it's n7ws at yahoo.com

Terry,

Chapter 2.

Chapter 3.

Let me know when you've got this so I can delete it. I'm at my storage limit.

Also, do you need the HP-IB codes at this time?

Wes

I had one of those too in "my" lab. I would sure give a K-buck for one. Where are you finding these deals?

Now you need an '8566B!

Um... IMHO the best spectrum analyzer ever built.

"Terry Given" a écrit dans le message de news:KtSue.9967$ snipped-for-privacy@news.xtra.co.nz...

I was lucky enough to get hold of an HP3585B for 400Euros. One point I didn't expected is that the fans noise (bearings or something like this) is, well, pretty present...

Does yours have the same 'feature' or is it just that mine needs some work?

I am (was), from time to time, looking for a used 3577 or 4195 VNA too, but these are rare and pretty expensive. I think you've got a good price for yours. Were did you get it?

Being desperate I finally decided to build my own one but, you know, so many things to do and not enough time...

--
Thanks,
Fred.

Hi Joerg,

I was pretty happy with it. I figured out your last point while reading the 3577 datasheet, so I spent $1000 and bought an HP3585A 20Hz - 40MHz speccy. Which I brought home at about 10pm on wednesday night. Then spent until 7am thursday morning playing with it, before driving up to auckland for a customer meeting *grin* - kid in a candy store.....

It was easy figuring out how to drive the speccy, but the NA is a bit trickier. The manuals should be here soon though. I have wanted both of these beasts for a *long* time. A place I worked at used to have a couple of Venables - one frequency response analyser, and one Dean. Man did I learn a lot.

Cheers Terry

I would really appreciate that, App notes are often where the gold resides. I'd gladly pay you to burn it to a CD and mail it to me, if its not too much trouble. I dont want to eat your bandwidth though.

Cheers Terry

Yee-ha! Thanks Wes, thats fantastic! Nice car, too :)

Regards, Terry Given

Hi Fred,

thats a good price. The fan on my one blows a howling gale, too. But its quiet compared to the 3577 :)

the 3577 came from Iomega corporation, via ebay. Its still got their property tag on it (#4043).

Cheers Terry