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Re: Measuring Capacitors
To elaborate on this a bit. Let’s think about a standard 0602 sized part - that’s 0.06” long or about 1.5 mm. A piece of wire that long has an inductance of about 1.5 nH.
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With, say, 33 pF, that’s resonant at 715 MHz. And yet, such parts are regularly used in all sorts of circuits at higher frequencies. You just design for the parasitic values. On Apr 2, 2025, at 20:14, Jim Lux via groups.io <jimlux@...> wrote: |
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Re: Measuring Capacitors
The max frequency is probably more about where losses get too big.
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And they’ll measure for a very wide range. Most design tools can deal with staying away from the SRF, if supplied with the part parameters. After all, at microwave frequencies most parts have a very complex and varying impedance. On Apr 2, 2025, at 15:34, Brian Beezley <k6sti@...> wrote: |
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Re: Jittery , non steady readings
Yes, it is
Zack W9SZ On Wed, Apr 2, 2025, 4:12 PM Dave Brown via groups.io <2c39a= [email protected]> wrote: Is the measurement frequency stable? |
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Re: Measuring Capacitors
By coincidence, I just added an image showing capacitance and dissipation factor plotted by my S-parameter plotter. It was derived from an .s2p file provided by Kyocera. Scroll to the last image:
One thing I don't understand. Manufacturers specify useful frequencies several times the capacitor self-resonant frequency, as revealed by the .s2p files they supply. The 33 pF shown departs from 33 pF as it approaches its 1.6 GHz SRF, which is nowhere near the 10 GHz specified upper frequency limit. All the capacitor manufacturers seems to do this. Why? Brian |
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Re: Jittery , non steady readings
Is the measurement frequency stable?
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Dave ZL3FJ -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Zack Widup via groups.io Sent: Thursday, April 03, 2025 06:14 To: [email protected] Subject: Re: [nanovna-users] Jittery , non steady readings I have consistently had this problem measuring inductors, capacitors and resistors. Just recently I measured a silver mica capacitor that was around 3400 pF. I measured at 475 kHz (630 meter amateur band). As I watched the display, every time I got a new measurement I would see something like 3420.1 3416.3 3411.8 3418.6 3422.5 3424.2 etc. I took the average of the measurements as the value. But I don't know why this was happening. The same happens with resistors and inductors. I could see the inductors as most likely to pick up radio signals. But I do not live close to a radio station or any service that is transmitting near me (as noted on a TinySA). I turned off my wifi and got the same results. I use a right angle SMA connector with a wire about 3 inches long going through the opening and soldered to the center pin contact, also another wire about 3 inches long soldered to the SMA body. I solder the other ends of the wires to the device under test. Zack W9SZ On Tue, Apr 1, 2025 at 2:51?PM kellogs via groups.io <mihai0226= [email protected]> wrote: Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in<> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> |
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Re: Jittery , non steady readings
I have consistently had this problem measuring inductors, capacitors and
resistors. Just recently I measured a silver mica capacitor that was around 3400 pF. I measured at 475 kHz (630 meter amateur band). As I watched the display, every time I got a new measurement I would see something like 3420.1 3416.3 3411.8 3418.6 3422.5 3424.2 etc. I took the average of the measurements as the value. But I don't know why this was happening. The same happens with resistors and inductors. I could see the inductors as most likely to pick up radio signals. But I do not live close to a radio station or any service that is transmitting near me (as noted on a TinySA). I turned off my wifi and got the same results. I use a right angle SMA connector with a wire about 3 inches long going through the opening and soldered to the center pin contact, also another wire about 3 inches long soldered to the SMA body. I solder the other ends of the wires to the device under test. Zack W9SZ On Tue, Apr 1, 2025 at 2:51?PM kellogs via groups.io <mihai0226= [email protected]> wrote: Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in<> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> |
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Re: Jittery , non steady readings
I was thinking that such fluctuations seen in NanoVNA were due to
swinging of my multi-band fan dipole in the wind! That would change the relative nearness of elements to each other and nearby structures. Jon, VU2JO On Wed, Apr 2, 2025 at 4:33?AM W0LEV via groups.io <davearea51a= [email protected]> wrote: If you have a close-by strong source of RF energy like FM or AM |
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Re: Jittery , non steady readings
Or to put it simply, the VNA contains a highly specialized radio receiver.
On Tue, 1 Apr 2025 23:03:04 +0000 "W0LEV via groups.io" <davearea51a@...> wrote: If you have a close-by strong source of RF energy like FM or AM-- 73 -Jim NU0C |
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Re: Measuring Capacitors
Nothing.. just some places block accesses to various countries, so finding alternate ways to get there is useful.
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There was a time when .int was resolved through a DNS server in China, which is blocked from government networks in the US. So if you had an alternate .org name, it was useful. On Mar 31, 2025, at 15:55, Dragan Milivojevic via groups.io <d.milivojevic@...> wrote: |
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Re: Jittery , non steady readings
If you have a close-by strong source of RF energy like FM or AM
broadcasters, police, ambulance, CB'ers, hams, ....... any of those and more could be affecting the readings. This is not all that uncommon in cities when the VNA is connected to a large antenna. Dave - W?LEV On Tue, Apr 1, 2025 at 7:51?PM kellogs via groups.io <mihai0226= [email protected]> wrote: Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in-- *Dave - W?LEV* -- Dave - W?LEV |
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Jittery , non steady readings
Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in 11+/-1.5 - j(70+/-1.5)
Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun and one at the VNA S11 port. No body / coax inadvertent movements, everything taped down near the antenna. Thanks |
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Re: NANO VNA H4 , Implausible measurement results?
No, but a guy may have already worked DXCC while you're still arguing about
whether an antenna is good or not. Get on and use it. Play with it later as needed. Zack W9SZ <> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Tue, Apr 1, 2025 at 10:34?AM W0LEV via groups.io <davearea51a= [email protected]> wrote: QUOTE: However a successful QSO is not scientific evidence of a "good" or |
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Re: I need help
Yes. Alan is one of the "big boys" and belongs to Tek. Those by amateurs
and others may be highly questionable. At least those are my experiences with YouToob. For example, addressing ferrites, Fair-Rite has a wonderfully useful and solid site, even some directly aimed at the amateur radio community. So do Agilent, Tek, Keysite, Advantest, R&S, HP, and many.....many others. To properly utilize YouToob presentations, one must first know at least the basics of the knowledge they are seeking. Without a basic knowledge, you are highly likely to be "snake oiled" and "witchcrafted" and "sorceried" and....... Dave - W?LEV On Tue, Apr 1, 2025 at 4:03?PM Donald S Brant Jr via groups.io <dsbrantjr= [email protected]> wrote: On Tue, Apr 1, 2025 at 11:36 AM, W0LEV wrote:--You can absolutely trust Alan Wolke W2AEW's videos. He is a Tektronix *Dave - W?LEV* -- Dave - W?LEV |
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Re: I need help
Even a linear wire, not coiled, has some measurable inductance. At zero
length the display on the Smith chart, will show a single value of zero at the extreme left of the real axis. That point on the Smith Chart is 0.00.... ± j 0 ohms. That represents a short circuit. As the measurement point along the linear wire is increased, both the RF resistance (skin effect) and inductance increase. Therefore, the measurement will depart upward on the chart (inductive reactance) and to the right along the central line on the chart. Since the vast majority of RF measurements are assumed in a 50-ohm system (the industry standard except for the television people), the chart is laid out around that value. ONLY the central point (see the previous attachment) represents 50 ± j0 ohms. The extreme right position along the central axis (real only) represents an open circuit or theoretically infinite resistance. An excellent tool both for analysis, modeling, and learning the Smith Chart is SimSmith. It's free and available at the following URL: That URL also contains many good tutorials addressing the Smith Chart. More information can be had at the following: Dave - W?LEV On Tue, Apr 1, 2025 at 3:52?PM Jon via groups.io <vu2jo0@...> wrote: Dave,-- *Dave - W?LEV* -- Dave - W?LEV |
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Re: I need help
On Tue, Apr 1, 2025 at 11:36 AM, W0LEV wrote:
You can absolutely trust Alan Wolke W2AEW's videos. He is a Tektronix Field Engineer, I know him personally and knows his stuff 100%. And, to your original question you must be looking at S11 Smith Chart display to see 50Ohms; S21 magnitude should be 0dB when the thru is connected. Best regards, Don Brant |
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Re: I need help
Dave,
One doubt about the Smith Chart: Why does the so-called resistive component change as you move across the tracing? If it was the true electrical resistance due to the ohmic resistance of the wire and feedline, it should not change. Forgive my ignorance. I have started using NanoVNA only recently. 73 VU2JO On Tue, Apr 1, 2025 at 9:15?PM W0LEV via groups.io <davearea51a= [email protected]> wrote: Possibly the attachment will help. |
Jim Shorney
Donald S Brant Jr
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