#2095

[@ats89117]

You could measure the S21 parameters with a VNA and show how the ferrite bead is inductive at low frequencies but resistive at higher frequencies.

[@jspencerg]

Today was reserved for playing with just repaired hp equipment. Checking for agreement between the vna's, etc would be an interesting rabbit hole. I've found my best cabling for measurements is semi- flexible coaxial with sma connectors.

[@PhattyMo]

It's been a long time since I was looking at ferrite bead specs,but yeah,I seem to recall 100Mhz as a common figure. I also seem to recall 70Mhz,for some reason. I was specifically looking for beads to block RF at VHF frequencies.

[@frankowalker4662]

🎉Happy New Year Everybody🎉

[@andymouse]

And you Frank.....Rip Calculon

[@frankowalker4662]

@@andymouse RIP Calculon 🧀 Mss you

[@Yonni6502]

@frankowalker4662 - and a Happy 2025 to you too! Woot! Another year in the bag. Who would have thought it? 😄

[@frankowalker4662]

@@Yonni6502 YAY

[@mkeyser]

I have the opposite problem! I'd love to have your HP there to measure my capacitor. What you're looking for is a Q meter, like a Boonton 190. Yes it is a dinosaur, and it's analog, but they are kinda fun to play with.

[@Mr.Leeroy]

Don't have to believe it, they are characterized pretty extensively. You just have to know the particular part number and the datasheet shows frequency dependent impedance curve similar to curve tracer readings for diodes. All the value of these things is in the manufacturer's data, otherwise they are pretty useless time costs wise.

[@SMShannon55]

Which is it, part 1 or part 2? 😅 You always make great content. I’ll watch them both.

[@chrisharper2658]

Why didn't you make an LR or LC network out of the bead and run a sweep on it with your spectrum analyzer?

[@craxd1]

XL = 2 x pi x F x L, so an increase in frequency raises the inductive reactance: XL (resistance to AC).

[@user-xlario]

But what he is measuring is the real part of the impedance, that is the resistance. The inductive part comes from the imaginary part, that is what you are saying.

[@larrysmall3521]

Use spring loaded test pins like used in test fixtures for your adapter.

[@TomSherwood-z5l]

SO if they were to say, measure it at two frequencies, could you then draw a line on a graph between the two and get something like an estimate for all the intermediate freqs?

[@SkippiiKai]

Can't you just use a $2 active 100mhz quartz crystal and measure it through the bead on your oscilloscope?

[@ygglw]

I would have really thought sweeping it with your NanoVNA would be able to show the ac impedance over a frequency range - that’s how I’d have measured it. If that is a bad idea can you say why so I learn something?

[@IMSAIGuy]

part 2

[@saravananKumar-o9m]

How many track tapping ji, comments pls

[@YSoreil]

Granted I'm a massive simpleton but isn't 100MHz really high speed for an LCR meter? I guess they have dedicated equipment to test these rather than a generic LCR meter in that case. Odd the common measurement speed is that high while a lot of other devices have very "old school" frequencies against which they are validated. Then again a ferrite bead is for high speed after all, not like the number written on the packaging would be of use to anyone if it was outside of the band in which it is operational. Never considered this problem, great video.

[@foogod4237]

Component specifications and ratings such as these are generally not done using generic testers like an LCR meter (even for things which theoretically could be). Typically, each one is tested by the manufacturer using its own specialized test circuit designed just for that specific part or series, to meet their precise testing specifications. In some datasheets they will even describe the exact test circuits which is/should be used (so people can replicate the tests exactly if desired, etc). And yeah, most manufacturers usually try to provide the values under conditions that are somewhere close to what the part is expected to be used for, so they are as relevant as possible for the people wanting to use them in a circuit. For most things, it is possible to extrapolate out to other conditions, but the further you have to diverge from the actual testing conditions, the less accurate you can be sure the result will be, so it's always best if the number on the datasheet is based on conditions that are close to the ones you actually care about.

[@MrMersh-ts7jl]

Is that resistance or impedance?

[@IMSAIGuy]

reactance

[@simontay4851]

Resistance and impedance are the same unit. Ohms. So it the same thing.

[@foogod4237]

@@simontay4851 Just because they're measured using the same units does not make them the same thing. Components such as these actually usually have very different resistance (DC effects) vs. reactance (AC effects) vs. impedance (resistance + reactance together), and which one you care about can depend a lot on the particular situation.

[@IMSAIGuy]

@@simontay4851 one is frequency dependent one is not

[@IMSAIGuy]

Impedance is a complex quantity given by: 𝑍 = 𝑅 + 𝑗𝑋 the LCR meter measures the absolute value of this complex number. yes both have ohms which is confusing.

[@glasslinger]

For optimum accuracy it is necessary to zero the instrument each time you change frequency.

[@ivanpopovic9503]

Actually no. If you do 'open' and 'short' ZERO, the instrument goes through all the frequencies from 10MHz to 10kHz and autozero itself, then keep the 'zero' in its memory until you hit 'ZERO' again. 4275A is quite fine piece of equipement, though >40yrs old.

[@glasslinger]

@@ivanpopovic9503 Can't fool me! I have one and have done 10 mhz testing. Forget to zero and the reading can be noticeably off.

[@ivanpopovic9503]

@@glasslinger Maybe your 4275A is not working as it should? I just did autozero, and then recheck zero at 10MHz, 4MHz, 2MHz, 1MHz, 400kHz, 200kHz, 100kHz, 40kHz, 20kHz and 10kHz separately with 16047A test fixture and the measured 'zeros' were almost identical (to +/-1 od least significant digit). Maybe I am doing something wrong? P.S. I did not intend to offend you by any means, I have deep respect for the work you show on your channel regarding tubes etc.

[@IMSAIGuy]

yes, my unit does a complete calibration at all frequencies when you push the button. no need to do it again.

[@ivanpopovic9503]

@@IMSAIGuy Well, then glasslinger has a problem with HP4274A, since mine works just like yours. Thanks.

[@nickcaruso]

You know what's a crazy idea? build a little uC based board that you can put in the power supply of your beloved (7904/HP4275/your fave here) and monitor the big power supply caps, and send you a text when things are going sideways. It could be powered by the residual voltage in the caps and only run when line is disconnected. That should be a fun project, right? 🙂

[@nickcaruso]

(I'll show myself out)

[@lmamakos]

That's the most amazing thing I've seen on KZbin. Manipulating an 0603 part in mid-air with tweezers, trying to get it stuck between a couple of springs and it not flying off to hide in a parallel dimension, never to be seen again. A Christmas Miracle, to be sure! I can just drop an 0603 part out of the tape, 4 inches off my workbench and never see it again. It's like the part and my anti-static mat are made of flubber - there's no other explanation on how things can bounce away at apparently supersonic speeds.

[@jspencerg]

I call them fleas.

[@markusm.lambers8893]

HNY 2025 ! de Markus - db9pz - JN39fq - 3miles/5km east of LX -