Re: 50ohm cal load failed
Well, my HP was calibrated decades ago before I retired. and like you say
for fun stuff it is good enough. I prefer to roll my own now. Close
enough is good for me.
Mel, K6KBE
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On Sat, Nov 2, 2019 at 12:57 PM hwalker <herbwalker2476@...> wrote: On Sat, Nov 2, 2019 at 10:46 AM, Mel Farrer, K6KBE wrote:
I have a set of SS SMA PCB mount male connectors that I soldered 4 200
ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
----------------------------------------------------------------------------------------------------------------
Mel,
I used a commercially made HP 50 ohm termination as my standard until
David Taylor pointed out that even though it was manufactured by HP its
s-parameter specs were lukewarm at best. My S11 measurements on known
devices were slightly off, but that was because my NanoVNA OSL calibration
was made with a load that was slightly off. Changing to a Mini-Circuits 50
ohm load with known s-parameter specs up to 18 GHz solved the problem. To
my point, what you have observed may not reflect accuracy unless your HP
termination is well characterized.
Of course if you are just using the NanoVNA in a hobbyist environment
where measurements within 5 - 10% are acceptable, then pretty much any 50
ohm load or termination assembled using good rf techniques should do.
- Herb
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Re: Nanovna data output: Use the following other FREE software
This file shows 3 software programs to get all the information you need
with antenna or component detailed Analysis.pdf
You can extract:
SWR - Standing Wave Ratio
Rs - Resistance, series form
Xs - Reactance, series form
Zmag - Impedance magnitude
Theta (deg) - Impedance angle
Rho (mag) - Reflection coefficient magnitude
RL (dB) - Return Loss, plotted as a negative number to show "reverse" scale (see note below)
Phase (deg) - Reflection coefficient angle
% Reflected Power
Q - Quality factor, |Xs| / Rs
Rp - Resistance, parallel form
Xp - Reactance, parallel form
Ls (?H) - Equivalent inductance for series Xs, both positive and negative
Cs (pF) - Equivalent capacitance for series Xs, both positive and negative
Lp (?H) - Equivalent inductance for parallel Xp, both positive and negative
Cp (pF) - Equivalent capacitance for parallel Xp, both positive and negative
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Re: 50ohm cal load failed
On Sat, Nov 2, 2019 at 10:46 AM, Mel Farrer, K6KBE wrote:
I have a set of SS SMA PCB mount male connectors that I soldered 4 200 ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
---------------------------------------------------------------------------------------------------------------- Mel, I used a commercially made HP 50 ohm termination as my standard until David Taylor pointed out that even though it was manufactured by HP its s-parameter specs were lukewarm at best. My S11 measurements on known devices were slightly off, but that was because my NanoVNA OSL calibration was made with a load that was slightly off. Changing to a Mini-Circuits 50 ohm load with known s-parameter specs up to 18 GHz solved the problem. To my point, what you have observed may not reflect accuracy unless your HP termination is well characterized. Of course if you are just using the NanoVNA in a hobbyist environment where measurements within 5 - 10% are acceptable, then pretty much any 50 ohm load or termination assembled using good rf techniques should do. - Herb
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Re: errors of "error" models
Sounds painful...
The Maxima install was uneventful here under Windows 10 on my desktop. It looks like learning how to use it is going to be my next hurdle. :-) I have verified that all three user interfaces appear to be working properly.
--
73
Gary, N3GO
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On 11/1/19 11:27 PM, hb9 iiu wrote: What are the chances that I brick my NanoVNA when trying to upload a new firmware? ???? Very, very slim, I would say.? There are probably several billion of those processors in use in various gadgets around the world, many of which get updated regularly.? Some people update their Nanos on a near daily basis, and the developers might update several or even dozens of times in a day.? I wouldn't worry about it.
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Re: Voltage sensing diode
Apologies - forgot the important bit.
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Re: Voltage sensing diode
On Sat, Nov 2, 2019 at 12:46 PM, Rich NE1EE wrote: I didn't know why you liked the BAV99 until I just looked them up. Nice! It's a $0.02 device! Puzzled because the BAV99 data sheet says VF=0.7V max @ 1mA, and we are well
below that...so I'd expect much less than 0,7V offset. Yet you report 4.2V for
a 1V offset. On the whole, I really like the approach. I am using both diodes in the BAV99 package in series hence Vf ~1V with VBATEN set and ~0.5V with VBATEN unset. We're interested in Vf @ 1.5uA and 40uA. See attachment from a Nat Semi data sheet 0.25V and 0.425V respectively. Conveniently very close to my measurements ;) YMMV depending on the manufacturer. A lot of manufacturers don't specify Vf properly at <1mA. So I measured my sample device using a 0-20V bench supply, a 200kOhm 1% resistor and a calibrated meter. If I try the resistors, I'll just put in vbat_offset=1000mV, and live with the
increasing (small) error as voltage drops. It would be interesting to see how well it works. It has the advantage that it is more or less self calibrating with 1% resistors. No doubt the firmware could be modified to suit.
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Re: 50ohm cal load failed
I have a set of SS SMA PCB mount male connectors that I soldered 4 200 ohms
0603 resistors around the clock, 12,3,6,9 and it measures very close to my
HP SMA termination.
Mel, K6KBE
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Show quoted text
On Sat, Nov 2, 2019 at 10:38 AM hwalker <herbwalker2476@...> wrote: On Sat, Nov 2, 2019 at 09:56 AM, QRP RX wrote:
It looks like cheap Chinese SMA-terminators. If so, they have bad
performance.
Try to measure it with multimeter, does it have 50.0 ohm?
Most of all it has high error, something like ¡À5 ohm.
----------------------------------------------------------------------------------------------------------------
As QRP replied, there is a difference between a 50 ohm termination and a
good quality 50 ohm calibration load. That is why commercial calibration
kits cost so much money. Using an un-characterized termination, your OSL
calibration will look correct but you will be referencing all your
measurements to however good the termination is. For example if you use a
poor termination for performing your OSL calibration and then measure a
good quality load. The load will look poor.
Checking the termination with a multimeter only tells you what its DC
characteristics are. You need to measure the termination against a known
good quality load to verify its characteristics. It might prove worthwhile
to construct your own 50 ohm load using the methods presented by other
members of this group.
Herb
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Re: Common Mode Current Impedance/Rejection
#test-jig
I have used several instruments and procedures to measure the isolation in dB, and impedance in ohms (calculated of course) using K9YC method and S21 on VNAs. They all come terribly close together. Care must be made in how the test jigs are set up and calibrated. With my setup, I can easily see return loss of 50-70 dB open circuit. I have pictures of the various ones I have used if you are interested. Mel, K6KBE On Sat, Nov 2, 2019 at 10:32 AM Mel Farrer, K6KBE via Groups.Io <farrermesa= [email protected]> wrote: Ed, Check the file section for Balun/choke investigation.
Mel, K6KBE
On Sat, Nov 2, 2019 at 10:23 AM Edward McCann <Ag6cx1@...> wrote:
Who have used the device to measure Impedance to Common Mode Current vs
frequency for bifilar and coax wound ferrite toroid of various materials?
Interested in a step-by-step procedure, which leads tied together,
measurements shield to shield, graphic results, and perhaps pictures of
test jigs, comments on tolerance, etc.
Thanks!!
Ed McCann
AG6CX
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Re: 50ohm cal load failed
On Sat, Nov 2, 2019 at 09:56 AM, QRP RX wrote:
It looks like cheap Chinese SMA-terminators. If so, they have bad performance.
Try to measure it with multimeter, does it have 50.0 ohm?
Most of all it has high error, something like ¡À5 ohm.
---------------------------------------------------------------------------------------------------------------- As QRP replied, there is a difference between a 50 ohm termination and a good quality 50 ohm calibration load. That is why commercial calibration kits cost so much money. Using an un-characterized termination, your OSL calibration will look correct but you will be referencing all your measurements to however good the termination is. For example if you use a poor termination for performing your OSL calibration and then measure a good quality load. The load will look poor. Checking the termination with a multimeter only tells you what its DC characteristics are. You need to measure the termination against a known good quality load to verify its characteristics. It might prove worthwhile to construct your own 50 ohm load using the methods presented by other members of this group. Herb
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Re: Common Mode Current Impedance/Rejection
#test-jig
Impedance to Common Mode Current vs frequency Some Wiki Application Notes page entries may be helpful /g/nanovna-users/wiki/Application-NotesCommon-mode chokes by G3TXQ ferrite bead measurements test jigs
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Re: Common Mode Current Impedance/Rejection
#test-jig
Ed, Check the file section for Balun/choke investigation.
Mel, K6KBE
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Show quoted text
On Sat, Nov 2, 2019 at 10:23 AM Edward McCann <Ag6cx1@...> wrote: Who have used the device to measure Impedance to Common Mode Current vs
frequency for bifilar and coax wound ferrite toroid of various materials?
Interested in a step-by-step procedure, which leads tied together,
measurements shield to shield, graphic results, and perhaps pictures of
test jigs, comments on tolerance, etc.
Thanks!!
Ed McCann
AG6CX
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Re: Console command and FW 0.2.3 edy555
You can use NanoVNA-Q firmware, it has scanraw command which don't have such
limit, but it returns raw measurements with no calibration corrections. For 'scan' command, which can return calibrated values, NanoVNA-Q firmware currently ignores the [points] value, always returning 101, but 'frequencies' returns the number of points requested. Using 'scan' command, e.g. in edy555 firmware, a shell script can combine multiple scans, e.g.: ch scan usage: scan {start(Hz)} {stop(Hz)} [points] ch pause ch scan 10000 100000 90 ch data 0 > data0.txt ch data 1 > data1.txt ch frequencies > freq.txt ch scan 100100 200100 90 ch data 0 >> data0.txt ch data 1 >> data1.txt ch frequencies >> freq.txt ...
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Common Mode Current Impedance/Rejection
#test-jig
Who have used the device to measure Impedance to Common Mode Current vs frequency for bifilar and coax wound ferrite toroid of various materials?
Interested in a step-by-step procedure, which leads tied together, measurements shield to shield, graphic results, and perhaps pictures of test jigs, comments on tolerance, etc.
Thanks!!
Ed McCann
AG6CX
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On 23/10/2019 20:21, John Nightingale via Groups.Io wrote: --------------snip------------------ A little note for new Linux users who find that Rune's application
is not seeing the NanoVNA when it is physically connected: root's
privileges will be required in running the application so that the
application is permitted to make a connection to the NanoVNA. If the
issue is that the application has not been permitted to open a port,
there will be a report to that effect in the console display.
Please don't encourage people to run Linux GUI applications as root. It's a very bad idea. It's likely that the regular user is not in the dialout group which is easily rectified by entering the following command in a terminal: sudo usermod -G dialout $USER You will then need to log out and back in once, after which nanovna-saver should always be run as a regular user. Cheers, Barry G4MKT
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Kurt wanted to see some pictures so here they are.
The first picture is the dB logmag of S11 of a 30cm semi rigid cable (medium) and a 1 meter RG58 cable (long), both Open and Short at the end, both from 0.5 MHz till 900MHz
When looking at the polar picture it is obvious the wobble of the logmag at lower frequencies is caused by a shift of the center of the open/short rotation as the lines do not cross (see third polar plot of the long cable 0-300MHz)
In the second picture a 106fF Open C0 correction is applied (as automatically calculated by Octave). This shifts the rotation just enough to remove the crossing of the Open/Short logmag
When I let Octave calculate a cable impedance correction (assuming a small mismatch between the cable impedance and Z0) I get the fourth picture shows almost no wobble. The impedance correction is a shift in the order of +0.025 + 0.5i ohm
For know I am running out of ideas on how to proceed as I do have no good model for the semi rigid cable
Anyone that knows how cables behave in a VNA?
Erik, PD0EK
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Re: 50ohm cal load failed
On Sat, Nov 2, 2019 at 06:50 PM, @arnoh wrote:
at RFPARTS to buy for 3,95$
It looks like cheap Chinese SMA-terminators. If so, they have bad performance. Try to measure it with multimeter, does it have 50.0 ohm? Most of all it has high error, something like ¡À5 ohm.
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Re: 50ohm cal load failed
Mine failed also - a piece of junk. Bought my own online.
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Re: Console command and FW 0.2.3 edy555
On Sat, Nov 2, 2019 at 06:47 PM, hwalker wrote:
On the other hand, its probably unclear to a lot of users how to generate the
equal number of calibration points to correct the raw measurements. Any
suggestions for doing so?
You can do scanraw for O,S,L cal-kit loads and use these results to calculate calibration corrections. After that just apply these corrections to a scanraw result.
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Re: 50ohm cal load failed
at RFPARTS to buy for 3,95$
Had recently gained bad experiece with cheap SMA-load baught via ebay (aro 1$ a piece), none of them had 50ohms,
so I discarded them, contacted the ebay dealer for replacement, got it, but they were no good either
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Jim Allyn - N7JA
Oristo
Arno DK3SS
