AKL-PT1 2 GHz passive oscilloscope probe

[jmw]

Plugging a campaign that I'd like to see get over the finish line:

https://www.kickstarter.com/projects/azonenberg/akl-pt1-2-ghz-passive-oscilloscope-probe
10:1 transmission line probe for 50Ω systems, 500Ω input impedance

Looks like a well-designed low-Z probe for a good price compared to spending for a commercial one or a lot of time tuning your own in Sonnet.

[nctnico]

Unfortunately 500 Ohm is too low. If you want to measure LVDS or something similar you'll be loading the signal way too much. In my experience you really want to be over 1k Ohm.

[Mechatrommer]

about 10 ohm loading at ~1GHz...  we are at the mercy of FR4 (or whatever substrate they are using) and a coaxial cable...

$150 is still an ouch for me, ymmv.

[nctnico]

There are better ways to spend $150 
Also 10 Ohm load @ 1GHz seems like a measurement error to me. Just based on capacitance that would translate to 16pf. Also the other measurements look fishy. Just look at the bandwidth graph; the commercial 1.5GHz probe doesn't even reach 1.5GHz (-3dB). I find that odd.

[JohnG]

The case is nice, and if they figured out a good way to put adjustable/replaceable tips on the probe while keeping acceptable performance, then that might be worth it to some people.

In the meantime, I've acquired a set of transmission line probes, 3 GHz and above, on ebay, for similar or less money, and I have built several.

500 ohms is low, I agree with really wanting 1 kohm, and really wish I could get more.

The comparison data seems sketchy to me. The $2k 0.99 pF probe is probably a FET probe with 100 kohm parallel resistance. I would take the comparison more seriously if they listed the probes to which they compared it. A picture of the setup used to measure the probes is just as important, otherwise the comparison is not very meaningful.

I do admit that even simple EM problems look much more impressive and are easier to sell to management if you have a nicely colored simulation  .

Finally, I would not be so quick to dismiss the importance of the coax cable quality. Just because it's rated for high bandwidth doesn't mean its good.

If the effort expended makes eventually results in a transmission line probe with better performance for similar money, that would be great, or if the price was more like $50. I don't see that the current iteration is much (or any?) better than I can do with a piece of high quality coax and a resistor.

John