Re: measuring Capacitance or Inductance
On Sun, Feb 14, 2021 at 03:59 PM, Bob Albert wrote:
I have measured electrolytic capacitors with my nano and they are woefully
bad at high frequencies.? Now that I have acquired a nanoVNA that can go down
to 10 kHz I plan to do some testing to see if they are just as bad at that
frequency.
Bob
Bob, I thought you might find this interesting. I took a small Siemens 10 uF 40V electrolytic and made some measurements on a DE-5000 RLC meter and compared them with the NanoVNA. At 10 kHz. and 100 kHz. The results were very close. Most manufacturers rate their electrolytics at 100 or 120 Hz. so these measurements are in the table below. You can see on the plots that this one went into self resonance at 420 kHz which is low and probably due to the fact that I left the leads at 1 inch long. Roger
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Here is a YouTube that shows how to use the NanoVNA as a spectrum analyzer.
So it can be done, but the results are not usually good enough to ensure emissions compliance. It is not really designed for this use. You must also limit the power input to very low values. I do not know the specifics but would assume less than +20 dBm or 100milliwatts. Anything higher would cause damage.
73
Evan
AC9TU
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Re: measuring Capacitance or Inductance
NWDZ board, like it says in the graphs. All calibrated on the same board with a single cable, as stated. And results were repeatable; I ran it several times. Are the board standards 100% accurate? Who knows? But the results were remarkably consistent over specific ranges.
--
Ed K9EK
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Maybe, but even at the low price, I can't see someone blowing up the device if we could prevent it. However, as I've stated before, experience is the best teacher. Dave - W?LEV On Mon, Feb 15, 2021 at 1:00 AM Dragan Milivojevic <d.milivojevic@...> wrote: Spoilsport ?
On Mon, 15 Feb 2021 at 01:31, David Eckhardt <davearea51a@...>
wrote:
To put things very bluntly, the NANOs have no place around a transmitter,
even 1 watt. It's circuitry without power, yes, but not at power.
Dave - W?LEV
-- *Dave - W?LEV* *Just Let Darwin Work*
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Spoilsport ?
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On Mon, 15 Feb 2021 at 01:31, David Eckhardt <davearea51a@...> wrote: To put things very bluntly, the NANOs have no place around a transmitter,
even 1 watt. It's circuitry without power, yes, but not at power.
Dave - W?LEV
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Roger TU for the reply I wish i understood what you are referring to? I went to the OneofEleven site and it is in GitHub I dont see an executable file which I could run. Darn, Your knowledge far exceeds mine.. Can you be more explicit? The Clearconfig 1234 same comment I am using Nanovnasharp.zip which becomes Nanovna.exe and is a great program It doesnt seem to hv a clear function ..
thank you Sir
Paul Kobetz
K2HZO
Rubicon Observatory
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Re: measuring Capacitance or Inductance
Ed,
In a previous post I asked you which RF Demo board you were using. I took a look at both models that are being sold and from the photos it looks like one has a better layout of the cal loads for open, short and load. Layout and parts placement will affect the reference plane. Photo attached.
Roger
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To put things very bluntly, the NANOs have no place around a transmitter, even 1 watt. It's circuitry without power, yes, but not at power. Dave - W?LEV On Sun, Feb 14, 2021 at 6:46 PM Dragan Milivojevic <d.milivojevic@...> wrote: I say go for it, 1.2W is nothing and the soldering lesson you will get
afterwards
will be a great learning experience.
On Sun, 14 Feb 2021 at 19:00, Cierra <dubosec@...> wrote:
Well, the radio is a QRP Pixie kit and it doesn't put out very much power;
I just wanted to test if I soldered the connections well. I have an analog
multimeter I could use as well. Eventually I plan to get (or make) a dummy
load, but I'm still practicing my soldering for now.
-- *Dave - W?LEV* *Just Let Darwin Work*
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Have you tried a Clearconfig 1234 from the USB Console using TeraTerm or the OneOfEleven NanoVNA app? It is discussed in the Wiki for this group. Once cleared do a Touch Cal, test Touch Cal and then Save. Go and do a full calibration and save to slot 0.
Roger
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My beautiful unit suddenly started to just start drawing lines all over the screen I hv recalibrated it several times.. Something is wrong as it was working fine. Question is there a reset ?? Is there a repair facility or is it just disposable ??
Thank You Paul Kobetz K2HZO Rubicon Observatory, Ukiah, Ca
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Since you¡¯re playing with transmitters, a dummy load is an indispensable
tool. If I were you, I would stop and make one before continuing with the
pixie.
It¡¯s simple enough to make one if you have some basic parts on hand. If
not, there are very cheap kits available for low power dummy loads. For
example, qrpguys.com has one for $10 which also gives you a dc voltage
proportional to the RF power you feed it. This will give you some
additional soldering practice, but more importantly will give you a way to
safely test qrp transmitters and measure their output power with your
multimeter.
A little dummy load like that will come in handy again and again as you
progress in your hobby. You will not regret it. I built a similar one into
a box with a dc meter movement years ago. Even though I have plenty of
other test equipment, that¡¯s what I reach for when it¡¯s time to smoke test
a QRP transmitter.
Good luck with your project and have fun!
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On Sun, Feb 14, 2021 at 12:00 PM Cierra <dubosec@...> wrote: Well, the radio is a QRP Pixie kit and it doesn't put out very much power;
I just wanted to test if I soldered the connections well. I have an analog
multimeter I could use as well. Eventually I plan to get (or make) a dummy
load, but I'm still practicing my soldering for now.
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Re: measuring Capacitance or Inductance
I have measured electrolytic capacitors with my nano and they are woefully bad at high frequencies.? Now that I have acquired a nanoVNA that can go down to 10 kHz I plan to do some testing to see if they are just as bad at that frequency.
Bob
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On Sunday, February 14, 2021, 03:55:40 PM PST, Dragan Milivojevic <d.milivojevic@...> wrote: That makes no sense whatsoever. On Sun, 14 Feb 2021 at 23:14, Manfred Mornhinweg <manfred@...> wrote: And what's the best bypass cap? Well, a single, plain, cheap aluminium
electrolytic!
Attached is the impedance plot for a 47?F, 25V electrolytic cap, measured
with lead lengths compatible with mounting it snugly on a PCB. Their narrow
pin spacing helps a lot in keeping their ESL low. I kept the same scale to
make comparison easy.
YES, a single 47?F electrolytic is a much better bypass cap than a
parallel combination of two ceramic caps of different values! Even in the
low VHF range!
The problems with electrolytic caps is that their ESR rises with age, and
rises much faster if they run hot, or if they have to carry large ripple
current. So they can't be applied in every situation. But in situations
that are kind to them, they are the cheapest and easiest way to get an
excellent wideband bypass.
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Re: measuring Capacitance or Inductance
That makes no sense whatsoever.
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On Sun, 14 Feb 2021 at 23:14, Manfred Mornhinweg <manfred@...> wrote: And what's the best bypass cap? Well, a single, plain, cheap aluminium
electrolytic!
Attached is the impedance plot for a 47?F, 25V electrolytic cap, measured
with lead lengths compatible with mounting it snugly on a PCB. Their narrow
pin spacing helps a lot in keeping their ESL low. I kept the same scale to
make comparison easy.
YES, a single 47?F electrolytic is a much better bypass cap than a
parallel combination of two ceramic caps of different values! Even in the
low VHF range!
The problems with electrolytic caps is that their ESR rises with age, and
rises much faster if they run hot, or if they have to carry large ripple
current. So they can't be applied in every situation. But in situations
that are kind to them, they are the cheapest and easiest way to get an
excellent wideband bypass.
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Re: measuring Capacitance or Inductance
Never........NEVER.......rely on an electrolytic as a bypass for RF energy!!!!!! Use series resonance to your advantage. Chip, N6CA learned that lesson from (deceased) Gary Frey, W6XJ, in the 1970's. The bypass caps presented in his preamps are chosen to be self resonant at the frequency of operation of each preamp. I've used the technique many times over in home brewing. It's a well known fact among (most) design engineers that tantalum capacitors are not much good above 500 kHz to a couple of MHz. Most electrolytics are even worse. Go measure them on your NANOs. I just grabbed a 1000 ?F / 25 VDC cap from the parts bin and measured it on a calibrated HP 8753C using the Smith Chart. Even at 1 MHz it measures 78 m¦¸ with a series reactance 78 nH. Sure, the DC portion is fine, but what is 78 nH at 50 MHz? X(L) = 2 x ¦Ð x f x L = 6.28 x [50 E 6] x [78 E-9] = 24.5 ohms Sure, the +j24.5 is non-dissipative, but does not make a very good bypass even at low VHF frequencies. Take a capacitor better suited as a bypass at HF, a 450 pF dip mica. Same setup at 10 MHz: 0.1 ohms at 462 pF. It goes self resonant just above 39 MHz. Which makes a better bypass at HF. Dave - W?LEV On Sun, Feb 14, 2021 at 10:14 PM Manfred Mornhinweg <manfred@...> wrote: And what's the best bypass cap? Well, a single, plain, cheap aluminium
electrolytic!
Attached is the impedance plot for a 47?F, 25V electrolytic cap, measured
with lead lengths compatible with mounting it snugly on a PCB. Their narrow
pin spacing helps a lot in keeping their ESL low. I kept the same scale to
make comparison easy.
YES, a single 47?F electrolytic is a much better bypass cap than a
parallel combination of two ceramic caps of different values! Even in the
low VHF range!
The problems with electrolytic caps is that their ESR rises with age, and
rises much faster if they run hot, or if they have to carry large ripple
current. So they can't be applied in every situation. But in situations
that are kind to them, they are the cheapest and easiest way to get an
excellent wideband bypass.
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: measuring Capacitance or Inductance
On Sun, Feb 14, 2021 at 12:25 PM, Ed Krome wrote:
Thank you to all who replied. But, since the values I was seeing didn't match
prescribed values (and it was driving me a bit nuts), I tried the experimental
approach. I took a single RF Demo Kit board with the same cable. I carefully
calibrated my 3 nanoVNA's (nanoVNA 2.8", nanoVNA H4, nanoVNA SAA-2N), each
50kHz to 300MHz. Then I recorded the values of the components at position 7
(capacitor) and posn. 8 (inductor) at increments over the frequency range.
Ed there are two versions of the RF demo board and at least 3 manufacturers. The test positions are different between the two. Photos of each attached. You can see that positions 7 and 8 on the NWDZ board are a capacitor and inductor respectively. However on the more commonly available DeepElec board 7 is a resistor and cap in series and 8 is an inductor and cap in series. Are you using the NWDZ board and are you using the short, open and load on that board to calibrate? Roger
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Re: measuring Capacitance or Inductance
Here is the phenomenon I referred to in a previous post in this thread.
[image: image.png]
This paper is written by Cadence and can be accessed at: Good to see that they show the parallel resonance between two different bypass caps! But too many circuit designers aren't aware of this.
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Re: measuring Capacitance or Inductance
And what's the best bypass cap? Well, a single, plain, cheap aluminium electrolytic!
Attached is the impedance plot for a 47?F, 25V electrolytic cap, measured with lead lengths compatible with mounting it snugly on a PCB. Their narrow pin spacing helps a lot in keeping their ESL low. I kept the same scale to make comparison easy.
YES, a single 47?F electrolytic is a much better bypass cap than a parallel combination of two ceramic caps of different values! Even in the low VHF range!
The problems with electrolytic caps is that their ESR rises with age, and rises much faster if they run hot, or if they have to carry large ripple current. So they can't be applied in every situation. But in situations that are kind to them, they are the cheapest and easiest way to get an excellent wideband bypass.
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Re: measuring Capacitance or Inductance
Here is the phenomenon I referred to in a previous post in this thread.
[image: image.png]
This paper is written by Cadence and can be accessed at:
Take only the 470 nF unit - the left in each plot. Below 15 MHz, the
device is capacitive, although decreasing in value as frequency is
increased. At resonance, it is purely resistive. Above resonance it
becomes inductive. The phase would also have to be shown to confirm that
last statement, but this is typical performance of a capacitor as it goes
through self resonance. Inductors act in a similar manner.
Dave - W?LEV
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On Sun, Feb 14, 2021 at 8:25 PM Ed Krome <e.krome@...> wrote: Thank you to all who replied. But, since the values I was seeing didn't
match prescribed values (and it was driving me a bit nuts), I tried the
experimental approach. I took a single RF Demo Kit board with the same
cable. I carefully calibrated my 3 nanoVNA's (nanoVNA 2.8", nanoVNA H4,
nanoVNA SAA-2N), each 50kHz to 300MHz. Then I recorded the values of the
components at position 7 (capacitor) and posn. 8 (inductor) at increments
over the frequency range. Results showed remarkably good correlation over
reduced frequency range on all three nano's. Pos. 7 showed the capacitor to
be 100pF from 0.1 to 100 MHz. Posn 8 showed the inductor to be 700nH from
0.1 to 30 MHz. Things went rapidly askew at higher frequencies, although
trends were similar. The capacitor lines followed each other reasonably
well all the way to 300 MHz on all 3 nano's, but the inductor curves, while
trending similarly, showed marked differences in values between the 3
different nano's. As a reality check, I measured the inductor on an AADE
L/C meter IIB and read 700nH. This wasn't as precise a setup as with the
nano's. Curves attached
I think I'm getting a handle on this now. Thanks again.
Ed K9EK
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: measuring Capacitance or Inductance
And since it's sunday and I have time for playing with the NanoVNA, I made measurements to show all of you the effect of placing bypass caps of different value in parallel. Attached are the impedance plots for 100nF alone, 1nF alone, and both in parallel. Whoa! Which option would you prefer?
Note that the 100nF cap alone provides a bypassing impedance below 3? from about 700kHz to about 70MHz. that's pretty good, I would say. The 1nF is bad on low frequencies, and the parallel combination is a total disaster! Yet that's what you will find in equipment designed by people who have never thought about this point, and are just following intuition, which often is wrong...
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Re: measuring Capacitance or Inductance
Dave, We warmed up the HP impedance meter of the time (the one that had a
tunable drum as a frequency indicator and topped out at 110 MHz). Sure
enough, *EVERY* CK05 capacitor went purely resistive between 1.4 and 1.6
MHz and inductive above that. What lead length did you use for that test????? After my last post I grabbed my box of 100nF capacitors, fired up the NanoVNA (works well even without warming up!), and measured two dozen of them, with lead lengths typical for PCB mounting. Their resonant frequencies all fell in the range of 6 to 8.4MHz. As was to be expected, the smallest ones (leaded ceramic chips) had the highest resonance, and the largest foil capacitors had the lowest, inside that range. I then measured with full length wires. My longest-legged one resonated at 1.85MHz. That one has 35mm long legs (each), of strongly magnetic material, which probably contributes to add lead inductance. To get those low resonant frequencies, you must have had very long-legged capacitors, like 5cm, and you must have measured them with full lead lengths. Of course nobody would mount a bypass cap with full-length leads! So what you were getting on those boards must have been much better. Resonating around 7MHz, and producing acceptable bypassing to 30MHz or so, depending on the impedance requirements. In a great many situations that's good enough, specially with older electronics.
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Roger Need
