Ping: Phil Hobbs

You should see what Don Nicols did to repair a piece of Tektronix equipment on the metalworking newsgroup. He made a new gear to rebuild an assembly that was 'replace only'.

--
You can't have a sense of humor, if you have no sense.

I don't smoke either but I do eat & drink in the car.

Interesting. Do you know where I could find the manual online? I'm interested in how well the arb function works.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

The TDS700 series doesn't accept knob inputs until the next screen update, which is annoying. Agilent periodically learns how to make scopes and then forgets again...e.g. by putting Windows on them. (Tek did that too, which is one reason why I'm sticking with the TDS600s.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

The theory is for an idealized abrupt junction, so I figured a varactor was a good place to start. An MV2101 had a non-ideality factor of about

1.04 near 0.5 mA, which was as good as I was likely to find. It was still noisier than 150 kelvin, although quieter than 300, which made it not too useful as a calibration standard. I went with varying the size of the input termination resistor, which will change the gain a little, but not too badly. A very small photodiode, tapped down on the 50 ohm termination so as to reduce the capacitive contribution, is probably the right answer (absent a dewar full of LN2).

The built-up circuit is a self-biased SKY65050 cascoded by a BFP650, running at a gain of about 20. Its noise is about 0.4 nV, and its input capacitance is around 0.8 pF including three pads, so I think it's probably about 0.3 pF barefoot. The hope is to wire-bond the pHEMT chip right to the DUT eventually.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

The 600 series is generally nicer, especially at slower sweep rates where the update delay in the 700s makes it harder to twist knobs and have them do what you expect. A bit like running a control loop through a satellite link, as in that Isaac Asimov story about the hot-hydrogen airship on Jupiter. My TDS744 is a very nice scope, which I use daily when I'm in the lab, so don't be discouraged about it.

(I got mine for very cheap in 2009--$900 including shipping, but the price of boat anchors has almost doubled since then--I'm averaging an outrageous 4 cents on the dollar instead of 2.) ;-)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

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OK thanks, The MV2101 looks like a rare beast. But I've got some other varactors in a drawer. (I figure some day I'll have a fairly good understanding of diodes and I can move on to those pesky three terminal devices :^)

That's too bad. I wonder where the excess noise comes from...Certainly you were above 1/f 'stuff'

I went with varying the size

Yeah, photodiodes are very nice, shot noise wise. (At least up to the MHz region.)

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Sounds nice. I sometimes get the feeling that just looking at a circuit adds a pF of C.

George H.

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It's not online and you'd be disappointed anyhow. It is in "Chinglish" and extremely brief. As in incomplete. What would you like to know about it?

--
Regards, Joerg

http://www.analogconsultants.com/

Today all the "Big 3" (Tek, Agilent, LeCroy) have Windows on their mid- to high-end scopes. I can't imagine this is going to change in, e.g., the next decade: People are now used to wanting to plug in pretty much any printer and have it work, fire up a browser to pull up a data sheet while the "scope" is running, run through data through some Matlab function (I know LeCroy and Tek support this, Agilent probably does too), etc. -- for the ~$50 or so it costs for an OEM copy of Windows, the manufacturers gain huge feature sets that they'd never be able (or at least willing) to pay to have their own guys implement.

The only reason you don't see Windows on low-end scopes is that for, e.g., a $1k scope you're probably looking at a manufacturing cost of

Nice.

Here's another pretty nice one:

(there are plenty on eBay).

Both of these are taking square aim at Agilent, right down to the shape of the box and the layout of the controls.

I believe it already exists, being marketed through some place called Highland Technologies... :-)

What was broken in it?

In the (one!) I've look at the internals of, there was a little O2E "module" that presumably cost a boatload of money, and the rest of the board was just power supplies, mostly.

---Joel

[...]

Although modern technology begins to take away the appeal of boat anchors. I always thought about buying a big HP spectrum analyzer that goes to several GHz. No longer, not after I took my little SignalHound USB spectrum analyzer on an EMC job recently.

The client had to set up an account with the rental place and that took too long. So I just packed my stuff, it's so small and light in weight. We ended up not needing the rental, saved a nice four-digit sum that way, the SignalHound and I sniffed out all the EMI hot spots, client went to the lab this week, nailed it.

Those USB thingies may be slower and have some drawback you must become familiar with. OTOH they can do things boat anchors can't. For example, one leak I only found because I could listen in via single-sideband demodulation. I have never seen a $xx,xxx analyzer that was able to do that. That feature alone has saved at least an hour last week and that's real money to clients.

--
Regards, Joerg

http://www.analogconsultants.com/

Exactly. And when that version of Windows goes out of support, you're hosed.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

I checked that out last week. Nice place :-)

I don't remember, something really simple.

I have seen some (but those weren't Thorlabs) where there were a few BFS17 or similar in there with filed-off identifiers. When I visit a client like that I usually have a small vial of BFS17 with me.

--
Regards, Joerg

http://www.analogconsultants.com/

My HP 8568B takes up a lot of rack space, but its close-in phase noise is unbeatable, and its amplitude calibration is amazingly stable and accurate. I sure wouldn't want to carry it in my tool bag, though.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

I have an Advantest R3361A SA that just do that :-) It even have a small speaker (OK far far from hi-fi) enclosed.

And I just discovered that my 8566B have sweep times down to 1us/div in zero span mode. This proved really useful when optimizing a pulse shaping filter of a 27MHz power modulator. Does your $0.000 USB SA allow this? :-)

--
Thanks,
Fred.

That's the one I was eyeing. But considering my lower back and the weight of that thing, not so great.

With my little USB thing I can use an external master clock but for close-in sensitive stuff I often use good communications receivers. Nothing beats a 300Hz 8-crystal filter. This is used when a client calls with a comment such as "We have this faint noise in the FFT but we can't find where it's coming from".

--
Regards, Joerg

http://www.analogconsultants.com/

Yup. Nobody's likely to steal it, though. The weight of all that stuff cracked the tire off my first set of casters, so I got some much wider, solid cast iron ones with hard polyurethane tires. Now it just puts dents in the floor tile. ;)

The filter doesn't help if the LO is a mess, though.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[...]

Ok, yeah, the LO on that receiver is of adequate quality. Else all the folks who spent hundreds of bucks on such a filter would be mighty miffed :-)

The only problem is that the bearing on that huge encoder wheel of this receiver is beginning to wear out. It will be a pain to replace.

--
Regards, Joerg

http://www.analogconsultants.com/

How about some nice engine honey?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net