#1215

[@clytle374]

Cool project and definitely a neat power supply trick for the bias.

[@rogerp5816]

Just seeing the impact of changing the SMA connector on the board made the whole video worthwhile. It just goes to show that the smallest of changes can have a very large impact when you're working at RF frequencies.

[@MrBrelindm]

I once reconditioned an 11-element, circularly polarized antenna for the two-meter amateur radio band. The most improvement in performance characteristics came from completely rebuilding the gamma match between the polarization planes of the antenna, and the physical straightening of the solid aluminum rod elements into two orthagonal planes. Not only was overall gain improved but the beam's main lobe was tightened improving selectivity as well.

[@Bobbias]

@@MrBrelindm I recognize some of these words... Actually basically all I get is straightening out the rods, and the tighter lobe/better selectivity... I need to learn some RF shit one of these days.

[@technishn]

If you calculate the resonace of the capacitor using your 100pF and 0.76nH it comes up to around 577 MHz, so you are probably seeing a series resonance effect, where the capacitor is now an inductor. A 100B datasheet confirms this. The ESR on the 100B datasheet shows ESR of ~ 50 milliohms and Q of around 60 at 500 MHz. Capacitive reactance is around 3 ohms at 500 MHz. There can be higher secondary resonances as well which the capacitor becomes a parallel tuned circuit.

[@kylerkidd4834]

That network analyzer is crazy. Smith charts are so cool

[@rafaelgcpp]

I would suggest the capacitor not being able to be a capacitor at 500MHz as the most probable cause of the "kink". The dielectric might act weird at higher frequencies and the pad resistance/inductance takes over

[@jakubniemczuk]

Your last cal was with the PCB on the thumbnail. Could you check how your 50 Ohm terminator is looking on the smith chart on the "through" trace? The second from the left.

[@jspencerg]

Wow. This exercise did so many things. I had been waiting for your reexamination of test board results before ordering some. Your results were great and added to ideas for best use. First, when did you get the bench top vna? Did you compare new instrument results to the nano, which you've already documented so well? I'd like to see your test board measurements compared on nanovna to give my results a reality check. Suggestions about validating using high end standards are interesting. Precision without accuracy is no good for the real pros watching(not me). Your comparison using port extension function and explaining results are appreciated. I've never seen the effort to actually compare results when measurement plane is extended, as it (mostly) happens. I'm living in the low GHz because that's what I can afford and it is what I need to learn. Seeing the effects of mm dimension changes are a great reminder of the magic of the RF world.

[@IMSAIGuy]

kzbin.info/www/bejne/iZLSk2ioa9OVlZY I did many video on the upgrade to VNA kzbin.info/www/bejne/eZu1l6ibbK2CndU comparison: kzbin.info/www/bejne/Z33Paox9r9-ootE

[@jspencerg]

@@IMSAIGuy Thanks for link. I'm just up to #700, not skipping around. Just enjoyed your special books segment.

[@theoldbigmoose]

Are these boards available for purchase? Only for your patreon? If available perhaps a link in the dubli doo?

[@IMSAIGuy]

I put a link in the description, they are available on my share site on PCBWAY

[@khimbittle7705]

nice video, prefer your rf videos because I am in learning mode for this as well,

[@1kreature]

Now cycle the temperature :)

[@thorhilda]

Interesting investigation. Thank you.

[@dixsusu]

What vna on market for hoby use woth to buy , other than mini-vna or the cheap onces , someting that looks like a osciloscop form factor ?

[@IMSAIGuy]

the siglent SVA1015X looks interesting

[@huawatuam4965]

I have somewhat mixed feelings about your video. You are measuring something "unknown" against "unknown" calibration standards until the result seems to make more sense to you. As long as you don't enter the correct/known calibration standard coefficients in your VNA, all these measurements are of little use in my oppinion. However - it was a nice video to watch :). How about sending your friend your cal-standard and he measures it agains his professional ones? That way you get a really known and good standard as reference yourself. Just don't forget to store the cal-coefficients in your VNA and recall them before you perform a calibration.

[@Mark-hb5zf]

I've done exactly what you've mentioned: Made my own cal standards for home use, but compared them to the Keysight calibration standards. I don't have the numbers in front of me, but I recall the return loss for S11 was better than 40dB for two 0603 100 ohm resistors in parallel when measuring to the Keysight calibration. The upper end was maybe in the 4GHz range (I typically measured out to 4 or 5GHz). I was quite pleased with the results given I just use them for hobby purposes at home on my HP 8753.

[@aduedc]

What is the objective here? To measure transmission line impedance or capacitor? If the objective is to measure transmission line your new calibration contraption would cancel out Transmission line imperfections, and you can not measure it correctly. I also think your body's proximity to the board change your measurement results.

[@Mark-hb5zf]

I don't want to imply I'm speaking for the IMSAI Guy, but I get the impression test boards were probably made without realizing the impact of the electrical length on measuring the part. Then it evolved into seeing how calibrating at the board edge vs. calibrating at the part reference plane makes a difference (along with not having an ideal 50 ohm trace). So likely a 'trial by error' scenario. I should add a full two-port cal would have been needed to really de-embed the part (if that was the goal). I noticed just a one-port cal was performed, so the transmission line on the other side of the part was not de-embedded. That would be the biggest contributor to device measurement error (if the trace is not an ideal 50 ohms).