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DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes

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tautech:
Spotted in another thread is a better description of flat ribbon coax cables like OEM's use for these LA probes:
Google: micro-coaxial ribbon cable

Lots out there and will be interesting to see what motivated hunters of such products can find.  :popcorn:

oz2cpu:
thanks for the hint, did a little googling :-) looks like it is clearly possible to get very thinn coax, and even in ribbon style,
however  : expect it will be a lot more work to hand solder, lower impedance..
and a lot more expensive / hard to get.
with the twisted pair : easy to get, chep, and easy to solder, and there is no detectable crosstalk..

oz2cpu:
NEW updated files :

the scope plug in pcb is now in V2.0
files are at the thingiverse link

V2.0 released 16 may 2021
 inner layers pulled back at gold finger ends,
 this way gnd copper will not be exposed when edge milled.
 0R resistor removed, the idea with this resistor : to be able to use the plug in pcb alone,
 if this feature is needed, use V1.0

mawyatt:
Great work!!

A couple notes regarding the newer PCBs. Don't see a spot for the lead cap in the POD PCB, this is in parallel with the high value resistor. When we assembled your POD PCB we had to stack the cap on top of the resistor, not so easy with 0603 SMDs. Also the terminating resistor at the scope side BASE doesn't actually terminate the transmission line since the input to the scope is relatively high Z. In fact the input terminating resistor doesn't do this either since the input probe lead is a large series inductance due to the actual probe leads, not to mention the ground lead inductance. The isn't as simple as just terminating with the line impedance at either end, look at my earlier post that shows the simulation which attempts to get a waveform at the scope connector that "looks" like the waveform tautech provided from the OEM LA. Figuring that "IF" the waveforms look similar, then the LA networks should be similar and the performance similar, I know at lot of "IFs" ::)

For these reasons when we did our PCB version we included the addition components to allow better control of the impedances "seen" at the input and output of the transmission line, wether it's a micro-coax, twisted pair, or simple ribbon cable.

Still waiting on the Dupont crimp tool, and sidetracked on another involved project (64 channel MMW phased array controller based on a new integrated technology voltage controlled transmission line for the delay elements), so hope to get back to this LA project soon.

Disregard the 0.1uF cap values shown in the schematic, obviously these should be in the few pF range!!

Best,

Bad_Driver:
I checked different old monitor cables as well. Old VGA cables have 3 thin coax with 75 ohms (measured) inside and other thin twisted cables.

But I will stay with twisted pair cables from DVI cables as suggested by Thomas. My interests are more on the "DC side" of digital electronics.
But it would be interesting to see if there are real differences with different cables and terminations up to 500 MHz. May be someone
tries it.

Unfortunately my 3D printer seems to suffer from a defective main board and needs much more efforts than I can spend these days.
So I cannot print the shells for the PCBs.  :phew: Hope to overcome this issue and be able to finalize the logic probe set. The tips arrived from Aliexpress.

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