Open source 2 GHZ Probe

[luudee]

Have you guys seen this ? This is amazing ?

https://jmw.name/projects/active-probe/

Anybody interested in a group build ?

Cheers,
rudi

[nctnico]

Have you guys seen this ? This is amazing ?

https://jmw.name/projects/active-probe/

Anybody interested in a group build ?

IMHO lasmux' probe is a much better option and not very expensive either. https://www.eevblog.com/forum/testgear/12-ghz-active-probe-project/

[tszaboo]

There is very little interesting things about a BUF802 probe, it's a known schematic, with relatively little variations in the components. For these probes the interesting part is the physical implementation, the probe holding, the different ground ground connections, the housing and the other parts that are ergonomics. There is little work done for this project on this part.

[jmw]

Hi, this is my project and write-up! This forum has been a great help along the way.

[Hydron]

Looks like an in-depth writeup, I look forward to reading it thanks (even though if I need a >1GHz active probe I would probably just buy the lasmux probe rather than build my own - my time cost would be much more than the very reasonable cost of that probe).

[jmw]

Of course. The Lasmux probe is a finished product and, by all indications, a fine one at that. As stated in the opening remarks, the goal here was advancing open hardware design in the T&M space. This design has not be "productized" but I have a small number of prototypes I am happy to send to those interested in testing and design feedback. Eventually I expect it will get to the point where it has an enclosure and accessories.

[MiroS]

Your project seems to be quite advance already, lasux probe is seems to be atractive from price pont, but probe is very noisy and interact higly with hand of operator.  Can you please show how noisy is your probe?

[luudee]

The way I see it, both probes need a shielded enclosure, and perhaps a smaller power jack on James version.
I would preferably power it from a larger Li-Ion pack close to the scope.

James, are you interested in making some changes to your design ?
Like making, it as small as possible, without compromising quality ?

I think it is great to have more than one solution out there !

Big thanks to both James and Lasmux !

rudi

[jmw]

Your project seems to be quite advance already, lasux probe is seems to be atractive from price pont, but probe is very noisy and interact higly with hand of operator.  Can you please show how noisy is your probe?

So I actually don't have a scope with enough bandwidth to measure the noise over 2 GHz of bandwidth. I can estimate it though: over DC–20 MHz, the measured rms output noise is 108 µV (after accounting for the scope), and then to 2 GHz with a brick wall factor of 1.1 and the BUF802 noise density of 2.3 nV/√Hz, it adds 107 µV, for a total of 215 µV rms at the output. Referred to the input (10x), this would be 2.1–2.2 mV of noise, on par with a Keysight N2796. I believe this is a bit better than Lasmux's latest result.

John, are you interested in making some changes to your design ?
Like making, it as small as possible, without compromising quality ?

Biggest obstacle to reducing size is the power jack, and I want something pretty easy-to-find, so I went with the 2.1x5.5mm barrel jack. Maybe with a flying lead connection to a barrel receptacle I can make the width smaller.

[luudee]

Hi James,


I would be happy with a two pin JLC style of a connector. I don't see this as being
something that I would ever unplug (at least on the probe side).

It would be really great if you can make it a bit smaller, and possibly add two mounting
holes.

Next we need an enclosure, preferable one that is isolating (plastic with metal coding,
or metal enclosure).


Cheers,
rudi

[jmw]

I like JST connectors for internal connectors, but a PH header is only 1.1 mm narrower than the barrel jack. I can get power adapters terminating in a barrel plug from anywhere or DIY a barrel plug-to-banana cable to use with a bench supply. PH connectors I really only see with batteries...

On making it smaller: two-sided assembly, 6 layers, and possibly separating the power connector to a free hanging inline receptacle could make the board a lot narrower. Definitely some tradeoffs to do that though.

[luudee]

I like JST connectors for internal connectors, but a PH header is only 1.1 mm narrower than the barrel jack. I can get power adapters terminating in a barrel plug from anywhere or DIY a barrel plug-to-banana cable to use with a bench supply. PH connectors I really only see with batteries...

On making it smaller: two-sided assembly, 6 layers, and possibly separating the power connector to a free hanging inline receptacle could make the board a lot narrower. Definitely some tradeoffs to do that though.

I would like the PH headers !  As I said, the power cable wouldn't be something I would ever disconnect, so soldering it would be just fine.

What kind of cable would you recommend between the probe and the scope ?

Best Regards,
rudi