Scope Probes off Ebay

Funny you should say that, but the 3.5Ghz probe I mentioned (a Tek P6056 to be precise) has a fragile resistor assembly in the tip according to the datasheet and it's easily damaged by rough handling. I'd be very interested to know what the secret sauce is in the Caddocks and why they're more robust than whatever Tek used in the P6056.

Many years ago when I was somewhat impecunious, I used to improvise like that, but these days I prefer to just buy whatever I need ready made. Some of those top-end RF patch cables can be ruinously expensive to buy ready-made, but what are you gonna do? No matter how good you are with terminations, you'll never emulate the quality standard of a properly made, high quality patch lead. When you're as ham-fisted and half-blind as I am, it's a no-brainer to buy 'em ready-made!

What do you mean by "fine"? How did you go about characterising them and what were you looking for specifically? IME you get what you pay for and cheap connectors are very seldom worth it. Buy cheap, buy twice as they say.

I did some consulting job recently. One of the guys insisted we buy the expensive probes, I carried on with my 900ohms 20:1 10 USD probe. By the way, the resistor on the end probe is not sensitive to pigtails, so in many cases it's better than the expensive probes

Which Caddock part number?

Thanks, I only looked at the pdf before. For usenet posterity the zip file contains Agilent document 54006-90002 and a photo of a probe made from a SMA connector with a resistor marked MD1248 950 1%, and a packet of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.

Not necessarily. I used to buy phase-matched sets of SMA cables from Huber & Suhner. Then, one day, because H+S did not reply to a new request for a quotation, I got them from JYEBAO in Taiwan via a French representative. They were cheaper *and* better.

Jeroen Belleman

This is comparison with sub pF probes vs just a resistor/coax. Seems the performance from the coax is very similar to high end active probe. From:

We do that with U.FL connectors. They're minorly fiddly, but seem to survive OK and work up to 6 GHz, so at the size of a SOT23 and a cost of only a few cents, they're Good Medicine. We often populate them for debug and then leave them off on production units.

We use them for I/O connectors in some products, as well--jumpers going from U.FL to bulkhead SMA are fairly inexpensive.

Cheers

Phil Hobbs

They have some interesting stuff for sure. Shame none of their site links work.

I do that too, also for all PSU rails. And add resistor in series with the feedback path of PSUs, then it real easy to do gain/phase measurements

I add 900ohm resistor on the board before the UFL, I guess you do the same?

High voltage dividers are another story.