futarisIRCcloud has quit [Quit: Connection closed for inactivity]
m4ssi has quit [Remote host closed the connection]
azonenberg_work has quit [Remote host closed the connection]
azonenberg_work has joined #scopehal
bvernoux has joined #scopehal
<bvernoux>
hello
<azonenberg>
o/
<azonenberg>
bvernoux: digikey was out of the MMCXes so i ordered them from mouser, they'll be here thursday
<bvernoux>
ha ok good
<azonenberg>
that's the last holdup i think until i send you the stuff
<bvernoux>
perfect
<azonenberg>
I have to make up a whole probe tip and everything too
<azonenberg>
i assume you do not want the probe pcb glued into the enclosure?
<bvernoux>
do you have found what is the issue with the probe tip ?
<azonenberg>
for easier testing best to be separate?
<azonenberg>
I have not
<bvernoux>
as it seems mainly related to it
<azonenberg>
What i did do was swap the tip with an edge launch SMA
<bvernoux>
if possible do not solder it on my probe
<azonenberg>
You want the tip not installed?
<bvernoux>
I will try with and without with measurements and accurate signal generator to check
<azonenberg>
OK
<azonenberg>
Maybe best if i send you one premade and one bare then
<bvernoux>
I will also check the tip alone
<bvernoux>
ha yes it will be very nice
<azonenberg>
So the issue is the tip is two separate conductors
<azonenberg>
the ground and the signal
<azonenberg>
it will be hard to test the tip in isolation
<bvernoux>
yes I need to check how I will test it
<azonenberg>
best option would be to de-embed by measuring the probe+tip and probe only, i think?
<bvernoux>
yes
<bvernoux>
to characterize both
<azonenberg>
I have two PCBs so i'll send you one with resistor+MMCX and one with resistor+MMCX+tip?
<bvernoux>
with S11 measurement & smith chart
<azonenberg>
i can include a second set of tip parts loose as well
<bvernoux>
yes perfect
<azonenberg>
Speaking of smith charts i need to do more reading to understand how to interpret them
<azonenberg>
i know of them, and i'd recognize one if i saw it
<azonenberg>
but i dont know how to read them yet
<bvernoux>
most important is S11 for that
<bvernoux>
and also check how it work on real circuit attenuation
<bvernoux>
...
<azonenberg>
also, s11? not s21?
<azonenberg>
for probe signal quality i'd think S21 is what you want
<bvernoux>
also S21
<bvernoux>
both
<azonenberg>
You should ideally see -26 dB S21 from DC to infinity
<azonenberg>
if the resistor is purely resistive and all impedances are perfectly matched
<azonenberg>
of course we know that isnt the case :)
<bvernoux>
yes
<bvernoux>
interesting point is we can deduce the Inductance & Capacitance of different elements
<azonenberg>
The other thing i want to try is adding a 9mm long open stub just behind the resistor, early qucs simulations suggest that this should null out some of the peaking i've been seeing
<bvernoux>
not deduce but compute ;)
<azonenberg>
but that was using an idealized model of the probe tip which doesn't map to experimental results as well as i'd like
<bvernoux>
interesting information on smith-charts