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On Mon, Jun 19, 2023 at 10:47 AM, n7wy wrote:

a vector network analyzer should not be further burdened with the functions of
a spectrum analyzer.

Yahbut you've already got the sweeping receivers and log amp/detectors, adding rudimentary SA functions is just code. That is why so many instruments, including from the big manufacturers, combine functions; the extra features have no incremental cost beyond the software development.
73, Don N2VGU

It works with the NanoVNA-app software and the screen is correct. But the -saver S21 is just a scatter pattern.

Help! Any idea what is wrong?

On 6/19/23 8:23 AM, RJOLLIS via groups.io wrote:

I have experienced a sudden and unexplained increase in the SWR of my HF antenna, I suspect the cheap coax or one of its pre-installed connectors. Before I chop the PL259s and install new ones, I tried to check for defects with the nanovna-h. There is no physical signs of damage. But I get an unexpected outcome.
Procedure. I have set up the VNA on Trace 0 in the Linear mode. VF is set to a nominal 80% for the 100 ft (30.5m) RG-8X coil of coax. The Transform function is selected and Low Pass mode is on. I sweep from 500Khz to 125Mhz. I get a spike at 14.79m. When I swap the inputs, the number doesn’t change. I would expect that if there was a short in the coax, I would observe 15.21m when I flip the ends.

That's pretty close to 50 ft. Sure it's a 100 ft coil?

Also, for a cable that long using the 101pt scan, you need to set your stop
frequency to about 70MHz to see the reflection from the whole length of the
cable. So what you are seeing now may be due to aliasing or something.
(I just experimented with the Transform settings with a 100ft length of
good cable on my -H4. When I had it at 400pt scan, 125MHz let me see much
longer than 100ft, but at 100pts I needed to set the frequency down to see
the reflection from the end of the cable. This is due to the "bin size"
used in the FFT.)


On Mon, Jun 19, 2023, 10:13 AM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

On Mon, Jun 19, 2023 at 08:23 AM, RJOLLIS wrote:

Procedure. I have set up the VNA on Trace 0 in the Linear mode. VF is

set to

a nominal 80% for the 100 ft (30.5m) RG-8X coil of coax. The Transform
function is selected and Low Pass mode is on. I sweep from 500Khz to

125Mhz. I

get a spike at 14.79m. When I swap the inputs, the number doesn’t

change. I

would expect that if there was a short in the coax, I would observe

15.21m

when I flip the ends.

Question. Am I doing something wrong here or do I have a defective nano?

I

haven’t yet characterized impedance or line loss. Those come next.

Looking at your photo your yellow trace shows S21 linear instead of S11
Linear.

I don't know what revision of firmware you have but recent firmware has a
Cable Measure function built in. Have you tried that?

Roger

On Mon, Jun 19, 2023 at 08:23 AM, RJOLLIS wrote:

Procedure. I have set up the VNA on Trace 0 in the Linear mode. VF is set to
a nominal 80% for the 100 ft (30.5m) RG-8X coil of coax. The Transform
function is selected and Low Pass mode is on. I sweep from 500Khz to 125Mhz. I
get a spike at 14.79m. When I swap the inputs, the number doesn’t change. I
would expect that if there was a short in the coax, I would observe 15.21m
when I flip the ends.

Question. Am I doing something wrong here or do I have a defective nano? I
haven’t yet characterized impedance or line loss. Those come next.

Looking at your photo your yellow trace shows S21 linear instead of S11 Linear.

I don't know what revision of firmware you have but recent firmware has a Cable Measure function built in. Have you tried that?

Roger

John. Thanks for your reply. Yes I have examined 2 meters each side of center. No issues are visible. That doesn’t mean that there is no damage. I will look at return loss and characteristic impedance later this afternoon. I would expect return loss would be impacted by a cable defect.

You didn't mention this but to me what you have determined is that there is
something causing an indication close to the centre of your coax, have you
visually inspected where the VNA is indicating where there is a problem?
Look very closely for signs of a pinch, puncture or other sign of damage.

What your VNA is telling you is that there is an issue somewhere close to
the centre of the coax, by turning the cable end for end and retesting, the
issue is within half a metre of centre.

That's what I get out of this anyway.

GL

John
VE7KKQ

On Mon, Jun 19, 2023 at 8:23?AM RJOLLIS via groups.io <rjollis=
[email protected]> wrote:

I have experienced a sudden and unexplained increase in the SWR of my HF
antenna, I suspect the cheap coax or one of its pre-installed connectors.
Before I chop the PL259s and install new ones, I tried to check for defects
with the nanovna-h. There is no physical signs of damage. But I get an
unexpected outcome.

Procedure. I have set up the VNA on Trace 0 in the Linear mode. VF is set
to a nominal 80% for the 100 ft (30.5m) RG-8X coil of coax. The Transform
function is selected and Low Pass mode is on. I sweep from 500Khz to
125Mhz. I get a spike at 14.79m. When I swap the inputs, the number doesn’t
change. I would expect that if there was a short in the coax, I would
observe 15.21m when I flip the ends.

Question. Am I doing something wrong here or do I have a defective nano? I
haven’t yet characterized impedance or line loss. Those come next.

Postscript: I note that I the pictures that I had attached show a sweep from 500Khz to 200Mhz. This was a photo setup error. When resetting the stop frequency to 125Mhz, the peak moves ever so slightly to 14.65m but the max length moves to 37m.

I have experienced a sudden and unexplained increase in the SWR of my HF antenna, I suspect the cheap coax or one of its pre-installed connectors. Before I chop the PL259s and install new ones, I tried to check for defects with the nanovna-h. There is no physical signs of damage. But I get an unexpected outcome.

Procedure. I have set up the VNA on Trace 0 in the Linear mode. VF is set to a nominal 80% for the 100 ft (30.5m) RG-8X coil of coax. The Transform function is selected and Low Pass mode is on. I sweep from 500Khz to 125Mhz. I get a spike at 14.79m. When I swap the inputs, the number doesn’t change. I would expect that if there was a short in the coax, I would observe 15.21m when I flip the ends.

Question. Am I doing something wrong here or do I have a defective nano? I haven’t yet characterized impedance or line loss. Those come next.

Jim is right, a vector network analyzer should not be further burdened with the functions of a spectrum analyzer. Bob - N7WY

female female?? or sma to reverse sma??

a friend grilled his 13cm amp with using a sma to reverse sma (accidently)

no contact ... swr sky high .. final amp went in semiconductor heaven

dg9bfc sigi


Am 19.06.2023 um 15:50 schrieb Muggs KC3UDZ:

Stan,

OK, I have found the problem... And it is ME!

First of all let me thank you for for explaining how to calibrate the NanoVNA; although I am well aware of how to do a calibration, it forced me to look at things more carefully.
In my attempt to extend the SMA connections and protect them I ordered some SMA Male-to-SMA Female connectors; OR SO I THOUGHT!
After taking everything down to bare-bones I noticed that the connectors are actually female-to-female! DUH!! I'm embarrassed and I feel like a complete IDIOT, but I put this "out there" as a reminder to others to check everything, even things you "know" are OK.
Anyway, thank you again and thanks for the "Absolute Beginners Guide" PDF; great resource.

Muggs KC3UDZ

The tiny SA ultra.....with it's 4" screen, will also measure 2 tone IMD of a linear amplifier, like imd 3-5-7....and also harmonic suppression of a linear amplifier.

Hi David,
The TinySA looks perfect for my needs - wow.

On 18/06/2023 11:14, erica edens wrote:

My issue is the output of the signal generator is unnknown and it would
be a useful feature at some future stage if 'namovna calibrated' signal
outputs were incorporated into its general design. I do not have much
tuning equipment, none of it is calibrated and I am simply looking for a
cheap and easy means to tune my antennas and rigs without turning my
shack into an RF lab!

Erica,

Yes, these devices are indeed remarkable! Many thanks for those who design and produce the devices and their extensive software.

For a calibrated signal generator (and highly functional spectrum analyser) you might like to look at the TinySA Ultra which is in stock in the UK:



Details:



The signal generator part of the spec is here:



I think you'll find the spectrum analyser function very useful in any case.

I have no relation to the firm other than as a very satisfied customer.

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

NanoVNA can`t change output (only 4 steps), also output depend from frequency

PS yes possible use external attenuator controlled by NanVNA over Serial, calibrate it. For this need software update (this also depend from Attenuator use)
PSS you can use TinySA for this

On Fri, Jun 9, 2023 at 12:29 AM, Steve Johnson wrote:

When using a NanoVNA to measure SWR on a multi-element antenna, with different
length elements but all fed from the same feedpoint, which element’s swr is
the Nanvna displaying data for?

What are your START and STOP frequency settings?
On which bands is the antenna supposed to work?
When I sweep a multiband antenna, the nanovna shows me the SWRs of all the resonances within the range of the sweep.
I have preset scan choices for 1.5 to 30 MHz and for 3.0 to 30 MHz sweeps, and it works very well. I see all the resonances on that one sweep setting.

The Nano will only show you what you actually tell it that you want to see.
--
Doug, K8RFT

Guys/gals,

I bought my nanovna H over a year ago and for such a small price, it is an amazing bit of kit.

Besides antenna tuning I use it for genera tuning of my rigs. I use it as a signal generator for RX alignment purposes. The nanovana whacks out a strong signal for alignment purposes and I use my homebrew signal reducer in order to carry out RX alignment purposes.

My issue is the output of the signal generator is unnknown and it would be a useful feature at some future stage if 'namovna calibrated' signal outputs were incorporated into its general design. I do not have much tuning equipment, none of it is calibrated and I am simply looking for a cheap and easy means to tune my antennas and rigs without turning my shack into an RF lab!

To everyone involved in the design, development and implementation of these devices, you have done an amazing job because you have made cheap access to a suite of analytical tools we could only dream of 50 years ago.

Ellis (G1PDA)

No, the nanovna has its own internal signal generator, and wouldn't work
with an external one.

The best way to check it is to calibrate it (calibration reset, then open,
short, load calibration). Then in normal trace mode, displaying the smith
chart, attach the same calibration standards one at a time and verify that
the short puts a dot at the left of the display, the load in the center,
and the open at the right. If this works, your nano should work fine to
show your antenna performance, like the SWR trace. See the "Absolute
Beginners Guide" in the files section of this group:
/g/nanovna-users/files/Absolute%20Beginner%20Guide%20to%20The%20NanoVNA/Absolute_Beginner_Guide_NanoVNA_v1_6.pdf
If the calibration doesn't work, then we have more troubleshooting to do.

Hello All,

My NanoVNA H4 is gone completely goofy. I cannot get a good reading from it on a known good antenna.
What would be the best way to test it for proper function? Can I take a reading from a signal generator set to something like 500KHz?

TIA,
Muggs KC3UDZ