<azonenberg>
I'm expecting my probes to ship any day now
<bvernoux>
yes great
<azonenberg>
also i ordered a 6 GHz pico 921 probe that should ship early march
<bvernoux>
ha great to compare with your probes ...
<azonenberg>
So we can do side by side testing of that, my homebrew probes, the low end pico probe, the lecroy active probe, etc
<bvernoux>
I shall solder other Probe Test Board v0.3
<bvernoux>
with better SMA connector
<bvernoux>
the AIM is to compare different SMA connectors
<azonenberg>
nice
<bvernoux>
first test was done with ultra cheap 0.1USD China SMA connector ;)
<bvernoux>
and the verdict is not good ;)
<bvernoux>
above 1.5GHz the connectors are awfull
<azonenberg>
Unsurprisingly
<azonenberg>
i'm amazed they work that far :p
<bvernoux>
yes it was expected ;)
<bvernoux>
But the question was how bad are they
<azonenberg>
Fair enough
<azonenberg>
also Pico has a 6 GHz VNA for somewhere around $5K iirc. My xaVNA is an amazing value for the money going out to ~3 GHz for $300ish but i'm not sure how much i trust the accuracy on the low end
<azonenberg>
lecroy's VNAs are $$$$
<azonenberg>
Very curious when and how much the Harmon one will be
<bvernoux>
yes
<bvernoux>
I will do a comparison of my xaVNA vs my HP VNA ;)
<bvernoux>
using same calibration reference which cost more than 600Euros
<bvernoux>
to be on par
<bvernoux>
the main difference is for dynamic range and accuracy anyway
<bvernoux>
HP VNA is up to 100dB dynamic range
<bvernoux>
xaVNA is something like 40dB ...
<bvernoux>
Also the biggest difference is reproductability
<bvernoux>
my HP VNA is amazing for that ;)
<bvernoux>
as there is a very nice OCXO inside and there is no drift at all
<bvernoux>
I have even connected a GPSDO to check that and there is not a lot of difference
<bvernoux>
xaVNA have a cheap TCXO or maybe even just a Crystal with 10ppm or more ...
<bvernoux>
It is a huge difference for stability
<bvernoux>
I do not even speak about components inside which drift ...
<bvernoux>
like resistors quality ...
<bvernoux>
a big surprise is my miniVNAPro2 which is quite good up to 120MHz ;)
<azonenberg>
yeah my clock distribution system is going to be built for stability
<bvernoux>
for NFC stuff is is very good as less heavy than using the HP VNA which is like to provide "caviar" to pigs when using it to characterize NFC stuff (up to 13.56Mhz or max 150Mhz for reflection of NFC Antenna) ;)
<azonenberg>
i'm looking at a fairly nice OCXO as the default clock source, with the option of an off board GPSDO module being added later on
<adamgreig>
it's a "hidden feature"? if you disable output 2 you get 1pps on it, synced to top of second
<azonenberg>
... oh, i looked at the other side SMA and thought that was clock out
<azonenberg>
didnt realize it was the antenna and it had two BNC outputs
<azonenberg>
Perfect, in that case i'll design my system without a GPSDO at all
<bvernoux>
yes I have no bought it because of BNC ;)
<azonenberg>
you'll have your choice of either no PPS and internal OCXO input, or external 10 MHz + PPS input
<bvernoux>
I use mainly SMA for everything (at least up to 26GHz ;)
<azonenberg>
i am moving to sma as much as i can but my scopes still have bnc inputs etc
<adamgreig>
his mini gpsdo has sma output, but no pps option
<bvernoux>
You know the fun
<bvernoux>
is with AirSpy I can see signal when output is turned off ;)
<azonenberg>
sub ps jitter he claims, i wonder what pll that's using
<bvernoux>
at -100dB ;)
<bvernoux>
using decimation by 64 with the integrated 12bits ADC / Tuner chain
<azonenberg>
My clock generation system will be built around a LMK04806
<adamgreig>
iirc it's a CS2100CP but i might be misremembering or outdated
<azonenberg>
Current plan is five front and five rear panel SMA outputs, 800 mV single ended LVPECL, on the main PLL
<azonenberg>
front and back outputs are grouped and share a common divider and bypassable phase shifter due to limitations of the PLL
<bvernoux>
clock gen is definitevely a must have especially if it can be synchronized with GPSDO or OCXO ...
<azonenberg>
So front 2 and back 2, for example, are always the same frequency
<azonenberg>
and either the same phase, or one is fixed at zero phase and the other is variable
<azonenberg>
front panel SMA deskew input for correcting for cable propagation delay up to 20 meters
<bvernoux>
yes it phase and level can be adjusted it is clearly a must have
<azonenberg>
Loop the far end of the cable out to the deskew input and tell it to deskew, and it will advance the phase until the leading edge hits the far end of the cable at the nominal zero phase point (or any phase offset you tell it to target) +/- 25 ps
<azonenberg>
Additionally, several front and rear LVCMOS18 and LVDS outputs driven by the FPGA
<azonenberg>
slightly higher jitter and, at least in initial firmware, no variable phase shift. But fully programmable output divider down to sub Hz
<azonenberg>
and arbitrary duty cycle if you want PPS etc
<azonenberg>
then gig-e driven by the FPGA with potential to eventually support 1588 in future firmware
<azonenberg>
front panel ~1" x 3" touchscreen display for viewing summary at a glance and maybe doing some basic adjustments, although i expect the lan interface to be the primary UI