S-parameter test sets

done, thanks, delete at will. and yes please wrt hp-ib codes, although now I have to save up and buy a usb-hpib adapter. I did some web browsing, and it looks like it will cost me US$400-$500, the latter price being the agilent box of tricks (which I will probably get). Looks like I'd better do some more work (in my now much-better-equipped lab) to earn enough to pay for it and the s-parameter test set.

Many thanks once again,

Regards Terry Given

Wow! 100Hz - 22GHz. A bit rich for my blood though :{

Now that I have the 3585, I can do all of my conducted emissions stuff. When I eventually get an HF speccy, it only needs to go down to ~ 10MHz, which (hopefully) means it'll cost less.

So many cool toys, so little cash.

Cheers Terry

Hello Terry,

If you don't need full speed it can be cheaper. I don't know whether this stuff is available in the US but in Europe they used to be cheaper than NI:

Seems prices have gone up since the 300k GPIB is now a whopping 285 Euros. These used to be around $100 or so. They also have a USB-GPIB but that's really expensive.

Regards, Joerg

[...]

Terry,

The GPIB bus is really simple. You can ignore most of the commands and just use the ones you need. There are plenty of examples that use the parallel port on your pc and a bit of glue logic to interface. Here's one, and google has lots more:

The trick in working with the gpib is to have a simple way to monitor the bus and set the data and command bits. Ziatech used to sell an inexpensive box for about $250 with a bunch of leds and switches that allowed you to act as a talker or listener and walk through all the bus transactions. It was very easy to use. You could make one yourself for the cost of the leds and switches. It is invaluable for debugging the interface.

Mike Monett

[...]

Hi Terry,

I usually find problems with outside hardware/software can take more than a day to solve. Intermittent failures, random software bugs, installation problems, data transfer errors, problems saving files and having them disappear, ad infinitum. When this happens, good luck getting support from the vendor.

The gpib interface is not that difficult, and is really easy to code. When you have done it yourself, you can easily fix any problems that might come up, and duplicate the system at very low cost.

A major problem with gpib is the interface is wire-or, so when you have an intermittent cable problem, it can be very difficult to troubleshoot. You don't know if it is in the equipment, or in the hardware or software, so you don't know where to start looking.

I have never seen diagnostics in commercial code that looks for any failure conditions, but you can easily add them to your own code.

YMMV, so best of luck. Let us know how it turns out.

Mike Monett

thats consistent with what I found - perhaps a dozen unknown brands, all around the US$300-$400 mark, and NI & agilent at $500.

Cheers Terry

You are missing most of the fun. In the olden days, the cables connected various 19 inch rack-mounted equipment.

When you had to move stuff to a demo, various ill-formed and smelly people arrived with dollies to take your precious and delicate instrumentation down 40 flights of stairs into a waiting van. From there, up 10 flights to the demo area.

It never made it. Vibration turned the 1 inch GPIB cable into a torture rack, severely distorting any connector that happened to be in the way, and rendering useless any equipment mistakenly connected during the transit.

I am in great favor of such moves. The next best thing would be a battery powered wireless connector that mounted on the rear of a gpib connector. Speff described such a device recently. The Zigbee. Perfect!

Keep looking. There will always be someone who makes AT-compatible interfaces.

I invested in 10 AT keyboards about 20 years ago, and they are still working.

So it is logical to assume I will still be able to buy motherboards that will connect to them. Otherwise my investment was for nought.

Hehe:)

Mike Monett

Mike Monett wrote: [...]

use

Hi Mike,

thanks for the link. I have also toyed with the idea of using a TUSB3210 (A USB micro I have used for other projects) to roll my own usb-to-HPIB converter. Then I have to write software to make it all go :{

If I could get the agilent USB interface for, say $200 it would be a no-brainer. Even at $500, it takes less than a days work to pay for it. I doubt I could get a system up and running in less time, so I'll probably just buy one.

Cheers Terry

Huh? The FCC requires testing well above 1GHz. WHen I was doing pre-compliance testing in the late '90s we had to show up to 6GHz (ten times our fastest clock).

There is no substitute for an analog spectrum analyzer. Any digital link would simply add a perceptable delay in the control response.

--
  Keith

interfaces.

Yes, I bow to the inevitable. We can still by motherboards with At-keyboard interface and serial and parallel ports at the local computer store. When that ends, I will have to scour the neighbourhood on garbage days and grab all the old computers that get thrown out.

So you see, it's a good thing I have learned to run on Win 3.11 and DOS. I can run on anything anyone wants to throw out.

I'm not kidding. My main computers died a while ago, and I am currently running on a 200MHz machine, with Linux and Win 95 on other ex-discarded machines. I also have a 66MHz 486 I'm looking forward to placing in service to do some control work.

Of course. To me, they are pure gold. I've been running this one for over

10 years. If the rest have the same reliability, I can expect another 100 years or so of excellent performance. Since I am somewhat over 60, that should more than satisfy the requirement:)

Mike Monett

Hello Mike,

The main problem I found with GPIB are those unwieldy garden hose type cables. Once I unhooked one and sure enough it recoiled, sending my half filled coffee mug sailing, crashing and spilling the contents all across the lab floor. On top of that it was my favorite mug.

I think Terry's path towards a TUSB uC may be a good one. Just imagine, replacing the garden hose with a USB cable from Walmart. Also, the cost for a 6ft cable would go from $100 or so to less than $10.

The only downside with USB is that its EMI performance is, well, not the best at times. RS232 would be better but many "modern" PCs don't have serial or parallel ports anymore. Oh well, out here we just keep a stack of ferrites handy.

Regards, Joerg

Hello Mike,

Maybe but when you have to use a laptop it's not that way. All but a few very high end (and thus high $$) laptops have done away with legacy ports. All they have is a few USB ports. You can buy cheap USB-parallel adapters but when it comes to two-way communication their performance sometimes becomes a bit rocky.

Did they appreciate in value? ;-)

Regards, Joerg

Hello Terry,

If it's for radiated EMI it won't need to go much past 1GHz either and the LO can be fairly loose.

What I am surprised about is that nobody seems to have come out with a "faceless" analyzer. Just a USB pod with a BNC jack would be fine. Or a glorified WLAN card with pre-converter and a BNC jack.

Regards, Joerg

Not to mention that they didn't always work. Some I had to wire in a star, others daisy-chained to get the damned instruments to talk. I always hated GPIB!

I'd prefer Cat-5 and Ethernet. Indeed, I'd rather have Ethernet than _any_ USB. Connecting a device across the Internet would be a little easier too. ;-)

--
  Keith

interfaces.

I'm a little confused here. AT keyboards and PS2 keyboards are compatible, electrically. ...just buy an adapter (either way) for $5 (I just threw a bunch out last week).

working.

Nothing but Model-M's here. This one is over 16 years old (Feb 17,

1989). ;-)

--
  Keith

Terry,

What didn't you like about it? I've used USB before, and while it is somewhat complex, if you're actually trying to achieve everything that USB does (power control, plug and play, guaranteed delivery as well as bulk delivery, "dumb" modes for initial boot of PCs with keyboards and mice as well as the standard "smart" modes, multiple speeds, etc.), I think that much of the complexity is needed. (I'd say the one place they got carried away was with control reads/writes... and once they let the "software guys" loose on defining stuff like HID, but that's no an inherent problem with USB itself).

---Joel

Hello Keith,

Depends on the product. The run of the mills stuff is often tested 30MHz to 1GHz radiated and 150kHz to 30MHz conducted. Most of the time there isn't anything to write home about above 500MHz.

True. However, for pre-compliance I often like small portable equipment. It doesn't have to be fancy. I shoot for 10-20dB margins which typically makes the product fly through the UL lab in a jiffy.

Regards, Joerg

Hello Mike,

Not necessarily. I know some folks here in town who are at least 20 years older and are happily pounding the keyboard.

Regards, Joerg

Hello Keith,

Agree. I always wondered why USB was conceived in the first place. It does have one advantage: Lots of DC power. Then again, two of the four CAT-5 pairs are usually vacant but the Ethernet standard lacked any power specs for a long time.

Regards, Joerg