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I have 2 bronze colored and 1 silver colored terminators. None of them measure 50 ohms! One of the bronze colored terminators has no center pin, so I am assuming that it is the open circuit terminator. A 50 ohm SMA terminator costs $4.45 on EBay.
wt1v

The 50 ohm is probably gray or partially gray with a center pin.

Mine had 3 plugs. One Silver with a Pin was the 50 ohm, One Gold with Pin, and One with No Pin.

Complain to the vendor.? However, 50 Ohm terminators are fairly common.? The only catch is that they are not pure at all frequencies so the one you use matters if you work at high frequency.? The resistance tolerance is important, as all your measurements assume it's 50 Ohms so if it isn't, say it's 1% high, all your readings will be 1% low.? Not too bad unless you are doing critical work.
Bob K6DDX

I am having a lot of problems with Nanovna Saver 401 point sweeps. I intermittent out of range errors when sweeping, but if I fiddle with resetting sweep points back and forth it sometimes works. Same problems using both firmware NanoVNA-H4_20210131.dfu as well as NanoVNA-H4.v1.0.64.dfu.

And so far I can only calibrate within the software using less than 401 points. I am pasting the log below.

Thank you to all!
Don

NanoVNASaver 0.3.9

Copyright (C) 2019, 2020 Rune B. Broberg
Copyright (C) 2020 NanoVNA-Saver Authors

This program comes with ABSOLUTELY NO WARRANTY
This program is licensed under the GNU General Public License version 3

See for further details.

Settings: C:/Users/d/AppData/Roaming/NanoVNASaver/NanoVNASaver.ini
2021-07-22 17:46:14,427 - NanoVNASaver.Hardware.Hardware - ERROR - No VNA detected. Hardware responded to CR with:
(null)?
ch>
2021-07-22 17:47:25,863 - NanoVNASaver.SweepWorker - ERROR - list index out of range
Traceback (most recent call last):
File "NanoVNASaver\SweepWorker.py", line 80, in run
File "NanoVNASaver\SweepWorker.py", line 121, in _run
File "NanoVNASaver\SweepWorker.py", line 236, in readAveragedSegment
File "NanoVNASaver\SweepWorker.py", line 264, in readSegment
File "NanoVNASaver\SweepWorker.py", line 279, in readData
File "NanoVNASaver\Hardware\NanoVNA.py", line 148, in readValues
IndexError: list index out of range
2021-07-22 17:52:20,341 - NanoVNASaver.SweepWorker - ERROR - list index out of range
Traceback (most recent call last):
File "NanoVNASaver\SweepWorker.py", line 80, in run
File "NanoVNASaver\SweepWorker.py", line 121, in _run
File "NanoVNASaver\SweepWorker.py", line 236, in readAveragedSegment
File "NanoVNASaver\SweepWorker.py", line 264, in readSegment
File "NanoVNASaver\SweepWorker.py", line 279, in readData
File "NanoVNASaver\Hardware\NanoVNA.py", line 148, in readValues
IndexError: list index out of range
2021-07-22 17:52:54,307 - NanoVNASaver.SweepWorker - ERROR - list index out of range
Traceback (most recent call last):
File "NanoVNASaver\SweepWorker.py", line 80, in run
File "NanoVNASaver\SweepWorker.py", line 121, in _run
File "NanoVNASaver\SweepWorker.py", line 236, in readAveragedSegment
File "NanoVNASaver\SweepWorker.py", line 264, in readSegment
File "NanoVNASaver\SweepWorker.py", line 279, in readData
File "NanoVNASaver\Hardware\NanoVNA.py", line 148, in readValues
IndexError: list index out of range
2021-07-22 17:56:21,441 - NanoVNASaver.SweepWorker - ERROR - list index out of range
Traceback (most recent call last):
File "NanoVNASaver\SweepWorker.py", line 80, in run
File "NanoVNASaver\SweepWorker.py", line 121, in _run
File "NanoVNASaver\SweepWorker.py", line 236, in readAveragedSegment
File "NanoVNASaver\SweepWorker.py", line 264, in readSegment
File "NanoVNASaver\SweepWorker.py", line 279, in readData
File "NanoVNASaver\Hardware\NanoVNA.py", line 148, in readValues
IndexError: list index out of range

I just got this unit today in the mail and upon inspecting it I found the main unit, a USB power cable, 2 SMA jumper cables, and a package containing 5 small items. There were 2 SMA barrel connectors, and 3 termination SMA plugs. 2 of these plugs have a male center pin and measure 0 ohms ( shorts), the last SMA plug has no center pin so I am assuming that it will be used to make the open circuit calibration. As far as I know, there should have been a 50 ohm SMA plug to do the calibration.and if this is so I have a problem in that I have a missing part. Otherwise the unit looks fine and powers up just OK. Anyone have any idea of what to do about the 50 ohm terminator that is missing?
syd / wt1v

Years ago before SMT parts at a previous employer one of the techs was building up a first run prototype board of a low power UHF transmitter for a wireless alarm system. He could not get the oscillator to work despite everything "looking" correct. The engineer came by to look at it and said "oh, you have that resistor in backwards". Huh?? The resistors were mounted in stand-up fashion due to the compact size of the board and he had one installed in the opposite orientation from what the solder mask indicated. The change in location of the lead inductance from one mounting orientation to the other was enough to kill the oscillator.

It seemed to me at the time that this was a circuit that was too close to the edge but not being an engineer myself I didn't say anything...

73

-Jim
NU0C




On Thu, 22 Jul 2021 10:10:01 -0700
"Jim Lux" <jim@...> wrote:

Or, even better, designing the circuit so it doesn't rely on undocumented behavior.

Absolutely!Thanks to everyone and also to the forum and it's providers.I've learned a lot from reading the many posts.I don't mean to hijack this post but when I read Roger's post I felt compelled to comment, thanks to all.DougVo1dwnSent from my Bell Samsung device over Canada's largest network.

Don't forget Dave and Dave, who provided everyone with the NanoVNA forum that facilitated the exchange of ideas that the aforementioned forum members built upon to provide everyone with what the 'Nano has evolved into !!


On Thu., 22 Jul. 2021 at 7:31 p.m., Roger<ve7vv@...> wrote: My new NanoVNA-H is working very well - it is an impressively capable, wonderful, little device!

I send along very big Thank-You's to edy555, HuGen and those who provided earlier designs for the hardware, to DisLord for new firmware, to Rune Broberg for the great NanoVNA-saver software that makes the hardware more practical and a delight to use and to all those others who have and continue to support this project. You have created a remarkable package that provides utility and pleasure to many people.

Best wishes to all of you.

Well said sir, I agree with your comments as I'm sure many others do as well.Very best to all and thanks for a truly wonderful little gadget.?Sent from my Bell Samsung device over Canada's largest network.

On 7/22/21 2:48 PM, Kent AA6P wrote:

Dave - I had one other thought. Would differences in Velocity Factor explain the different results?

The velocity factor can vary quite a bit across different types of coax. I really noticed that when using the TLDetails program from AC6LA software. There is also a big difference between solid dielectric and foam.

A different velocity factor would change the electrical length of the transmission line. That would change the frequency differences between the various peaks and valleys.

I believe my cable is 14 feet 10 inches plus another 6 inches for the SMA to SO-239 adapter.

Sure.. what phase shift do you measure with the far end open at your frequency of interest.. Divide by 2, and that's your cable length (electrically)

My new NanoVNA-H is working very well - it is an impressively capable, wonderful, little device!

I send along very big Thank-You's to edy555, HuGen and those who provided earlier designs for the hardware, to DisLord for new firmware, to Rune Broberg for the great NanoVNA-saver software that makes the hardware more practical and a delight to use and to all those others who have and continue to support this project. You have created a remarkable package that provides utility and pleasure to many people.

Best wishes to all of you.

Dave - I had one other thought. Would differences in Velocity Factor explain the different results?

The velocity factor can vary quite a bit across different types of coax. I really noticed that when using the TLDetails program from AC6LA software. There is also a big difference between solid dielectric and foam.

A different velocity factor would change the electrical length of the transmission line. That would change the frequency differences between the various peaks and valleys.

I believe my cable is 14 feet 10 inches plus another 6 inches for the SMA to SO-239 adapter.

73, Kent
AA6P

On Thu, Jul 22, 2021 at 10:07 AM, Lou W7HV wrote:

Certainly in production you can run into problems relying an unspecified
characteristic of a component. Those characteristics may be different from
different vendors

That's why you have an approved vendor list, and only allow purchasing from that list. You still have to worry about the possibility of your approved vendor changing their part, but at least you don't have to worry about the vendor-to-vendor variations.

A company I worked for once upon a time had to recall and rework a considerable amount of product after the purchasing agent bought something that engineering hadn't approved, because "the salesman said this was just as good." It wasn't.

Thanks so much Jim, Dave, and Ron for your replies and all the information. I really appreciate the modeling and all the documents. I will need some time to review and understand all this information.

The coax is marked RG-58A/U on the outer jacket. It was purchased 40 years ago but is in perfect condition and has never been used outside. It is a smaller diameter than RG-8X or RG-59 and requires a thicker reducer when used with a PL-259 connector. I am actually using a UG-176 reducer but with some RG-8X outer jacket placed over the smaller coax.

The Smith Chart circles are centered on 50 ohms. I tried a 25 foot length of RG-8X and the Smith Chart circles were also centered on 50 ohms. However, with the longer feed line the frequency difference between the various peaks was about 15 MHz rather than 24 MHz.

I'll check the Smith Chart one more time with the RG-58A/U.

I attached an image of the adapter used for the calibration at the end of the coax cable. It may not be ideal, but it appears to work over a reasonable frequency range and it also allows use of the SMA calibration standards supplied with each NanoVNA.

73, Kent
AA6P

Raspberry Pi wants to be a Bluetooth host, not a Bluetooth client.

I’m sure there are ways to do it the other way around, but it doesn’t work that way out of the box.

73, Willie N1JBJ

On Thu, Jul 22, 2021 at 09:55 AM, Jim Lux wrote:

Then you can use any wireless interface available on the Pi

Funny you posted that.
I am up to my eyeballs in playing with Bluetooth and just found out that NOBODY can tell me what is the passcodde to get into RPi.
My OS identifies two HC_05 and I can get in one with 1234 passcode.

It does identify my RPi with name, but I do not know the passcode .
Tried 0000 and it did not work.

Well I got RPi few inches next to nanoVNA but I think just replacing the USB cable with Bluetooth would be more KISS.
I think if you "warm-up / /charge" the nanoVNA first then replace the cable with Bluetooth would be slick.

On Wed, Jul 21, 2021 at 06:27 AM, Jim Lux wrote:

On 7/20/21 7:11 PM, Roger Need via groups.io wrote:

How did you calibrate? If you keep clips at a fixed distance during

calibration and measurement you will get better results.

calibrated using a 50 ohm BNC load, a BNC short, and left it open.

Yes, if I were to tape the leads down, it would probably work better,
but this was a first try at a "rough and ready" measurement

You will get much better results if you calibrate using the clips as the "reference plane". You just clamp them in a fixed position a short distance apart and then use a shorting wire, an open and a 50 ohm resistor (two 100 in parallel with short leads) to calibrate. Results are OK for HF but not much above that.

For serious measurements you need a much better test jig. I use this one made from an SMA female connector and some pin sockets/

Roger

Or, even better, designing the circuit so it doesn't rely on undocumented behavior.

Certainly in production you can run into problems relying an unspecified characteristic of a component. Those characteristics may be different from different vendors and may become different from a given vendor if it changes is process, materials, or design in ways the doesn't affect and may improved the specified characteristics. If you really need or want to do that, lot testing of that component can help spot potential problems. .