Re: Scope Probes off Ebay

On 07-04-2024 18:57, John Larkin wrote:

On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
wrote:
 

I never learn. I bought a used "Agilent 500Mhz probe" off Ebay for 50
quid as the highest bandwidth probe I thought I had was a 150Mhz Tek
one. Anyway, I have a large selection of old probes lying around so
decided to check to make sure the "Agilent" one was genuine. Not
surprisingly it turns out it isn't. I haven't calculated what it's
real bandwidth is. I've established it's not as sensitive as the
150Mhz one and that's all I need to know. Whilst I was going through
this palarva, I tested a old probe I came across that I've never used
before and was amazed at the improvement in signal I got with it. I've
just Googled its part number and it turns out it's a 3.5Ghz passive
probe! I never even knew I had one so fast. I would never have ordered
the "500Mhz" one if I'd known I had this forgotten-about one already.
So the fake's going back for a refund and I won't be ordering  any
more probes from anywhere in the forseeable future.

 The HP54006 is a 6 GHz probe, into a 50 ohm scope.
 https://www.dropbox.com/s/lxq4ujmkvo755uy/HP54006_probe.zip?dl=0
 They show up on ebay now and then. There's one now, asking $150.
 You can make your own with some of those Caddock resistors. The
Caddocks have some magical recipe. And unlike a fet probe, they are
hard to damage. I use them to probe 7 ns 1400 volt spikes in my
Pockels Cell driver.
 And you can do a GHz at least with a 1-cent axial or mini-MELF or 0805
resistor on the end of a coax. 450 ohms makes a 10:1 probe. Fast
circuits are often low impedance circuits and don't mind a 500r or 1K
load.
 

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