azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing | | Logs:
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<azonenberg> So i think i'm ready to try inserting this filter i've been playing with into the actual AKL-PT1 layout
<azonenberg> it's a fan stub in series with a 50 ohm FC0402 resistor with a carefully sized ground cutout under it
<Bird|otherbox> notching out the wifi eh?
<azonenberg> No
<azonenberg> There's two unrelated issues
<azonenberg> the first is that the AKL-PD1 differential tip has length roughly equal to a full wave dipole for 2.4 GHz ISM band
<azonenberg> And the amplifier has poor CMRR so we end up getting lots of wifi in the output
<azonenberg> I have ferrites arriving next business day to try eliminating the common mode component of the signal more completely
<azonenberg> The second is that the AKL-PT1 handheld probe has a resonance in the tip that i can't really do much about
<azonenberg> Which produces peaking in the response
<Bird|otherbox> aaah
<azonenberg> So i'm trying to create a notch filter with Q matched to the tip resonance
<azonenberg> and, the tricky bit, stopband attenuation closely matched to the height of the peaking
<azonenberg> i don't want 4-6 GHz gone, i want it weakened enough to produce an overall flat response
<Bird|otherbox> yeah, that's definitely tricky alright
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<bvernoux> hello
<bvernoux> I have feedback from Rigol EU about MSO5000 SCPI slowness
<azonenberg> bvernoux: oh?
<bvernoux> yes ;)
<bvernoux> I'm doing a summary of all SCPI commands which are dead slow on RIGOL MSO5k
<bvernoux> he will try my code on github to reproduce the issue
<bvernoux> as it contains all timing and bottlneck
<azonenberg> Great
<azonenberg> Keep us posted
<bvernoux> yes
<bvernoux> I have provided him a full example with 100 Waveform captured with 10kpt and 200MSPS
<bvernoux> to show that 4chan 4x10kpts(40KBytes) take 1s ;)
<bvernoux> especially the Trigger is crazy slow
<bvernoux> 610ms !!
<bvernoux> with 10MHz signal as input with simple trigger on rising edge
<bvernoux> it is same with 100Mhz signal ;)
<bvernoux> Summary is pretty clear
<bvernoux> Acq Time min=0.9200s, max=1.2500s, avg=1.0338s(0.037 MBytes/s), nb_waveform_cnt=100, nb_total_acq_failed=0
<azonenberg> Great
<azonenberg> Let me know if they fix it
<bvernoux> yes
<bvernoux> the guy told me he was not aware of that issue
<bvernoux> which clearly show everyone have that slowness issue
<bvernoux> and even more in that thread as the SCPI are pretty buggy ;)
<bvernoux> there is an internal synchro problem to acquire CHAN1 DATA ...
<bvernoux> to completely fix it I need to use FFT on the oscilloscpe especially with >1Mpts ;)
<azonenberg> Awesome
<bvernoux> I have coded a way to retry anyway which work fine
<azonenberg> Tek replied to me about the MSO6 issues too, i forget if you were around when i mentioned
<bvernoux> ha and what they replied ?
<azonenberg> but i will likely be getting a loaner MSO6 soon with beta firmware that hopefully solves some of them
<azonenberg> they apparently redid a lot of the scpi code recently
<bvernoux> ha great news
<bvernoux> maybe they could provide you a MSO6 freely during few months ;)
<bvernoux> the reference is clearly Picoscope today do you have some new bench on your Pico6000 ?
<azonenberg> I have no new data, no. I haven't touched it, been busy with other stuff
<azonenberg> However, i do have some updates on the differential probe
<bvernoux> ha great
<bvernoux> what are the result with diff probe ?
<azonenberg> 1) the LeCroy D400A-AT shows wifi interference too when the tips are floating. Quite substantial i may add. I forget if i tested tips shorted together or not
<azonenberg> Maybe i can just turn down the power level on my AP and be fine
<azonenberg> But it's not just my designs having this problem
<azonenberg> 2) My pack of ferrites from digikey came in a few minutes ago
<azonenberg> i'm about to test the improvement they may make in CMRR on the AKL-AD1
<azonenberg> no results yet
<bvernoux> ha yes interesting
<bvernoux> yes WIFI is a real mess today ;)
<azonenberg> Also i've been doing a bunch of sonnet sims on the AKL-PT1 to try and flatten the response
<bvernoux> it is easy to build an antenna with such probe ;)
<azonenberg> some interesting findings i dont fully understand, it seems i actually have two issues
<azonenberg> one is the dip early on, two is the 5 GHz peaking from the tip
<bvernoux> you need a spectrum analyzer to check if that does not come from your lab this 5GHz
<bvernoux> like the 2.4GHz Wifi mess ;)
<bvernoux> on my side I have bought a Netgear R7800 ;)
<bvernoux> and it is very nice for the price especially when upgraded with OpenWRT
<bvernoux> it is a must have ;)
<bvernoux> of course I use an USB 3.0 key for the storage else there is only 80MB free in internal flash
<bvernoux> with an external USB 3.0 key dongle it is very fast with speed test up to 240MB/s ;)
<bvernoux> it can be even used like a NAS with eSATA port (and few USB 3.0 free port too)
<bvernoux> and the power consumption is only about 10W so it is not bad for something running all the time
<Famine> amusing wifi anecdote, my ISP disabled manual channel selection on the supplied router with the reasoning automatic channel selection was superior... the router always selected the most congested channel after that
<azonenberg> The peaking shows up in the VNA, very smooth. not a narrowband peak
<azonenberg> shahriar saw it too
<azonenberg> I use Ubuquiti commercial APs and have had good results, but left them on default power settings
<azonenberg> I might want to lower power on the lab one for EMC reasons
<azonenberg> it's about 2 meters from my bench line of sight
<azonenberg> Anyway, current test setup is AKL-AD1 with output direclty into 50 ohm scope input
<azonenberg> glscopeclient FFT+waterfall
<azonenberg> AKL-PD1 connected to amplifier with tip contacts shorted together
<azonenberg> About -33 dBm in the wifi channel 11 band
<azonenberg> Now to add the ferrite
<azonenberg> With the tip inputs floating instead of grounded i get about -35 dBm
<azonenberg> Ferrite added, tips shorted to ground, -39 dBm
<azonenberg> So basically the ferrite gives me 6 dB of extra noise rejection
<azonenberg> It helped, but not nearly as much as i wanted
<azonenberg> now to try stick-on ferrite sheets
<bvernoux> azonenberg, especially in USA WIFI is strong ;)
<Famine> i'm thinking i need to order a few thousand jfets, onsemi is EOLing a ton of them now
<azonenberg> Using scope measurement power levels, with no ferrite i have about 36 mV p-p noise with the inputs shorted, 40 mV floating
<azonenberg> with slide on ferrite, floating, 37 mV
<azonenberg> so again it helps, but not much
<bvernoux> in USA max TX power is up to 1000mW ;)
<bvernoux> when it is 100mW max in EU (ETSI)
<bvernoux> My router is configurable up to 30dBm (1000mW)...
<bvernoux> I'm not sure the manual configuration is effective anyway I will check that ;)
<bvernoux> as when it detect the country it shall restrict to the maximum power in the country
<azonenberg> Aaaand no measurable benefit from stick-on ferrite it looks
<azonenberg> Three of the slide-on ferrites definitely produces a measurable benefit
<azonenberg> but that is a lot :p
<azonenberg> And i seill am seeing substantial noise
<azonenberg> still*
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<Bird|otherbox> azonenberg, "wifi is like cat hair: it gets in everything and causes trouble when it does"
<azonenberg> lol
<azonenberg> Yeah i'm going to investigate that more later, right now i'm busy simulating tweaks to the AKL-PT1 again
<azonenberg> I have that dip around 2 GHz i need to figure out