On Thu, Apr 3, 2025 at 08:11 AM, alan victor wrote:
The R and L for above SRF of the C serves as a DC block
while adding a stabilizing R and an L for the match.
I had guessed the DC block above SRF might be useful even when C was not the LF value. Thanks for the insight on R and L, Alan. Brian
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Well.....here's another one for you: SM inductors. Most of the suppliers quote Q at 1 MHz. 1) The RF "resistance" (due to skin effect) should be used instead of the DC resistance. 2) Outside of RFI suppression, who really uses them at 1 MHz. Where are the plots of Q vs. frequency? Or RF "resistance" vs. frequency? This is why I always source MuRata who gets it right. CoilCraft? No. Dave - W?LEV On Wed, Apr 2, 2025 at 10:34?PM Brian Beezley via groups.io <k6sti= [email protected]> wrote: 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
-- *Dave - W?LEV* -- Dave - W?LEV
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On Wed, Apr 2, 2025 at 03:34 PM, Brian Beezley wrote:
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?
This is common practice in microwave power amplifiers and and some MMIC designs as one component brings in two. The R and L for above SRF of the C serves as a DC block while adding a stabilizing R and an L for the match. The same tactic is used with distributive L. First glance at some PA designs will most likely not make sense without recognizing that the parasitic is used to advantage. A complete sim is required adding in all device models including the passives.
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On Thu, Apr 3, 2025 at 06:21 AM, Jim Lux wrote:
You just design for the parasitic values.
That's what I finally guessed designers must do. Check out the Y21 method plot for capacitance I just posted for a different capacitor. Above the first two resonances, capacitance returns to a positive value, though not the LF or rated value. Brian
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On Wed, Apr 2, 2025 at 08:14 PM, Jim Lux wrote:
And they¡¯ll measure for a very wide range.
After looking at more .s2p capacitor files, I've concluded that the file comments refer to the measurement frequency range, not the recommended frequency range for the part. I've attached S-parameters for an 82 pF porcelain capacitor that are pretty wild. Capacitance calculated with the S21 and Y21 series-through methods differ greatly. Brian
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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.
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.
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On Apr 2, 2025, at 20:14, Jim Lux via groups.io <jimlux@...> wrote:
?The max frequency is probably more about where losses get too big.
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:
?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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The max frequency is probably more about where losses get too big.
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.
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On Apr 2, 2025, at 15:34, Brian Beezley <k6sti@...> wrote:
?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
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?
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
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
<
Virus-free.www.avg.com
<
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
|
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
|
Re: Jittery , non steady readings
Is the measurement frequency stable?
Dave
ZL3FJ
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-----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
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
<> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
|
On 2025-04-02 01:03, Fran?ois via groups.io wrote: Too bad it doesn't lead to any practical use. What do you expect me to do with a deadly formula like this?
Fran?ois, on dit en anglais <<maths moche!>>, "ugly math". John, at radio station VE7AOV.
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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
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
<> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
|
Re: Jittery , non steady readings
I live in a quiet neighbourhood; the antenna measures 8 cm from tip to tip. I shall take some measurements at the countryside and report back when I do.
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Too bad it doesn't lead to any practical use. What do you expect me to do with a deadly formula like this?
--
F1AMM
Fran?ois
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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
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
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
--
*Dave - W?LEV*
--
Dave - W?LEV
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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
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
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 -- 73 -Jim NU0C
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Nothing.. just some places block accesses to various countries, so finding alternate ways to get there is useful.
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.
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On Mar 31, 2025, at 15:55, Dragan Milivojevic via groups.io <d.milivojevic@...> wrote:
?Your first link redirects to the same url the OP posted but I got to ask:
What is your issue with the paper being hosted in Bosnia&Hertzegovina,
the paper originated there.
On Mon, 31 Mar 2025 at 20:44, Jim Lux via groups.io <jimlux=
[email protected]> wrote:
Other sources that are in other countries than Bosnia Hertzegovina
The authors have a number of other interesting "measure component with a
VNA"
Measuring impedances of DC-biased inductors by using vector network
analyzers
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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
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
-- *Dave - W?LEV* -- Dave - W?LEV
|
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
|
Jim Shorney