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I have ordered two batches of boards from JLCPCB for the QEX September/October 2021 “Miniature SMA Step Attenuator” pp 9-21 by Tom Alldred VA7TA. There is a quantity of excess PCBs available. I do not anticipate that I will place another order, but I will continue to accept orders until my supply is gone.

More information is available on my web page

I expect to receive the second set boards near the end of October. The first board orders will be mailed next week about October 5, 2021.

Dick K9IVB

On 9/27/21 12:58 PM, Jim Lux wrote:

I'm trying to control a second nanovna (identified as HW V3.5. FW version 1.0.45) with nanovna.py and I'm getting an error



jimlux$ ./nanovna.py? --start 1000000 --stop 2000000 --points 201 -o test9 --port 0
{'rawwave': None, 'plot': False, 'smith': False, 'polar': False, 'delay': False, 'groupdelay': False, 'vswr': False, 'phase': False, 'unwrapphase': False, 'tdr': False, 'scan': False, 'start': 1000000.0, 'stop': 2000000.0, 'points': 201, 'port': 0, 'device': None, 'verbose': False, 'capture': None, 'command': None, 'save': 'test9'}
[]
1000000.0 2000000.0 201
set_frequencies 1000000.0 2000000.0 201
Traceback (most recent call last):
? File "./nanovna.py", line 422, in <module>
??? n.write_touchstone(opt.save)
? File "/Users/jimlux/opt/anaconda3/lib/python3.8/site-packages/skrf/network.py", line 1958, in write_touchstone
??? + c2str_A(self.s[f, 0, 0]) + ' ' \
IndexError: index 100 is out of bounds for axis 0 with size 100


works fine on an older version of the firmware on a different device.

I suspect there's some command that's being sent (or not being sent).

Before I start digging in, if anyone has had a similar issue, what was it...


Here's a good run (FW version 0.4.5-1)


jimlux$ ./nanovna.py? --start 1000000 --stop 2000000 --points 201 -o test9 --port 0
{'rawwave': None, 'plot': False, 'smith': False, 'polar': False, 'delay': False, 'groupdelay': False, 'vswr': False, 'phase': False, 'unwrapphase': False, 'tdr': False, 'scan': False, 'start': 1000000.0, 'stop': 2000000.0, 'points': 201, 'port': 0, 'device': None, 'verbose': False, 'capture': None, 'command': None, 'save': 'test9'}
[]
1000000.0 2000000.0 201
set_frequencies 1000000.0 2000000.0 201
(base) MT-211249:nanovna jimlux$

Turns out that the new firmware doesn't support the "port" command. I'm not sure if it's useful anyway, I think it was tied to the dump raw samples, which is also removed.?? you still need the --port %d on the command line, because that's how you distinguish between S21 and S22 for an output file.

I'm trying to control a second nanovna (identified as HW V3.5. FW version 1.0.45) with nanovna.py and I'm getting an error



jimlux$ ./nanovna.py? --start 1000000 --stop 2000000 --points 201 -o test9 --port 0
{'rawwave': None, 'plot': False, 'smith': False, 'polar': False, 'delay': False, 'groupdelay': False, 'vswr': False, 'phase': False, 'unwrapphase': False, 'tdr': False, 'scan': False, 'start': 1000000.0, 'stop': 2000000.0, 'points': 201, 'port': 0, 'device': None, 'verbose': False, 'capture': None, 'command': None, 'save': 'test9'}
[]
1000000.0 2000000.0 201
set_frequencies 1000000.0 2000000.0 201
Traceback (most recent call last):
? File "./nanovna.py", line 422, in <module>
??? n.write_touchstone(opt.save)
? File "/Users/jimlux/opt/anaconda3/lib/python3.8/site-packages/skrf/network.py", line 1958, in write_touchstone
??? + c2str_A(self.s[f, 0, 0]) + ' ' \
IndexError: index 100 is out of bounds for axis 0 with size 100


works fine on an older version of the firmware on a different device.

I suspect there's some command that's being sent (or not being sent).

Before I start digging in, if anyone has had a similar issue, what was it...


Here's a good run (FW version 0.4.5-1)


jimlux$ ./nanovna.py? --start 1000000 --stop 2000000 --points 201 -o test9 --port 0
{'rawwave': None, 'plot': False, 'smith': False, 'polar': False, 'delay': False, 'groupdelay': False, 'vswr': False, 'phase': False, 'unwrapphase': False, 'tdr': False, 'scan': False, 'start': 1000000.0, 'stop': 2000000.0, 'points': 201, 'port': 0, 'device': None, 'verbose': False, 'capture': None, 'command': None, 'save': 'test9'}
[]
1000000.0 2000000.0 201
set_frequencies 1000000.0 2000000.0 201
(base) MT-211249:nanovna jimlux$

NanoVNA have L/C Match function (Marker->Measure->L/C Math in last firmware)
This function calculate how compensate measured impedance to 50 Om

Albert,

My take... When one talks of distributed circuits like a coax cable or
waveguides, the space (and time) origin to solve the Maxwell equations must
be set: in the case of guided propagation like in the coax/waveguide
examples, the propagation occurs in one direction (along the cable) and the
fields are essentially solved on the (x,y) plane where they stay the same
because they do not propagate.

Since the measurement the NanoVNA offers is ideally under steady state
conditions (where the solution to the Maxwell equations is not too
complicated), the reference plane can be thought of as the point in space
along the direction of propagation where the phase of the incident signal
is set to 0.

Hope it makes sense, it's a nice question!

Thanks,
Luciano



On Sat, Sep 25, 2021, 11:23 AM kk7xo via groups.io <kk7xo=
[email protected]> wrote:

As far as I can tell, calibration is done at a single point in a circuit.
A plane suggests two dimensions, and that anywhere on that two dimensional
object, the calibration is the same. But everyone knows that even for a
solid copper plane, only one point can be considered 0 volts, and every
other point on that plane has resistance, inductance, and capacitance
relative to that one point.
So, why do people talk about the "plane" of calibration, rather than the
point of calibration?

73 de Albert KK7XO

You could define it as a POINT on the Smith Chart (the impedance coordinates or the mag and angle of the reflection coef at that point).

Hi Albert,

Just so you know your question posted although you didn't ask who does not use the NanoVNA with waveguides. I have no need of waveguides at the frequencies where I live.

73,

Bill KU8H

bark less - wag more

OK, I buy this. So another question, how many of you use the NanoVNA with waveguides?

de Albert KK7XO

It's a two-dimensional boundary separating two three-dimensional regions, hence "plane".

Phil M1GWZ

There are actually two charts as you can see overlaid, usually in two colors to assist reading. The chart on your vna is the Z plane chart. After rotating it 180 degrees it becomes an admittance chart. Upon over laying the 2 charts, the composite chart is referred to as the IMMITANCE chart. The charts Together facilitate conversion of series complex impedances to parallel complex admittances. That process in it self assists in simple impedance matching or transforming Z from one level to another. There is a simple algebra proof and manipulation of converting a series circuit to its parallel equivalent. The chart does the process graphically. However, it is worth going through the math once to see how it develops. Then I think you will understand better the MOTIONS on the chart as you add series and shunt elements to build a match network.

On 9/25/21 9:07 AM, alan victor wrote:

In some calibration systems like TRL, using transmission lines, thru, reflect, line... The cal pieces actually are a PLANE sheet, the various line edges which serve as the cal junction. So not a point but a surface extending the width of the line in MICROSTRIP as one case.

In the case of waveguide, where scattering parameters and such were originally used, there is a "plane", cutting across the waveguide.? One hopes, of course, that you're using waveguide that supports only one mode, but that does make it more interesting if it does support multiple modes.? Even for coax, you're looking at a transverse electric field between the center and shield, so there's a plane that cuts across the propagation path.

I'd never have thought to use jumpers at hundreds of MHz, assuming they'd be too reflective. Though I admit, I've done little work at hundreds of MHz. Nice work!

I see what appears to be quite small ground vias along the lines. Is this a quasi copanar waveguide?

I've got to put a test structure like this on a TDR and see how it looks!

I look at the calibration plane as dividing electrical space in two with the measurement system on one side and the DUT on the other. The calibration of the measurement system occurs at the plane. Everything on the other side of the plane is what gets measured.

I might add, waveguides fall under the same class and the use of a plane across the flange of the guide is apparent.

In some calibration systems like TRL, using transmission lines, thru, reflect, line... The cal pieces actually are a PLANE sheet, the various line edges which serve as the cal junction. So not a point but a surface extending the width of the line in MICROSTRIP as one case.

As far as I can tell, calibration is done at a single point in a circuit. A plane suggests two dimensions, and that anywhere on that two dimensional object, the calibration is the same. But everyone knows that even for a solid copper plane, only one point can be considered 0 volts, and every other point on that plane has resistance, inductance, and capacitance relative to that one point.
So, why do people talk about the "plane" of calibration, rather than the point of calibration?

73 de Albert KK7XO

Success! Removal of the FM9688 and adding the jumper did the trick. The nVNA starts up every time.
I'm using an external battery pack with it.
Thanks!
--Al

You can try to remove the FM9688 first in order to confirm if it is caused by a fault in the FM9688.

On Sat, Sep 25, 2021 at 08:43 AM, Hugen wrote:

It looks like the power IC is malfunctioning, so if you are willing to work without the battery, try removing the FM9688 and shorting pin4 and pin8 of the FM9688 location on the PCB.

Hugen, thank you for your reply. Do you think it's worth trying to replace the FM9688 IC? I have some experience and equipment to work on SMD and that chip has enough spacing of its leads to make it seem reasonable to give it a try.

--Al

On Sat, Sep 25, 2021 at 07:57 AM, William Smith wrote:

Try disconnecting the battery, disconnecting the USB cable, powering it on to discharge any caps, and then boot it with just the USB as power supply? Battery might be getting soft...

Thanks for the suggestion. I tried it, but all I get is a more dramatic flickering of the display at a slower rate.

--Al