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A true TDR sends out a short pulse and looks at the time it takes for that pulse to return.
The NANO VNA sweeps frequency and notes where the frequency when reflected impedance approaches Infinity and Zero Ohms.? ? ?Different resonate points? ?Then calculates the length of the line from it's resonate points.Same result, different methods.??
I own 3 TDR's and a good TDR will show you where along the line the coax has been stepped on, has a defect, or even where some water has leaked into the line.? The Nano is not going to get to those levels, but what do you expect for 20 dB less money?? ??
The Nano works in the Frequency Domain, a TDR? (Time Domain Reflectometer) works in the Time Domain.So technically the Nano is not a TDR.? ? But gives a similar answer.? ? ? ?Kent WA5VJB? For many years an Applications Engineer with Tektronix.?




On Tuesday, June 20, 2023 at 07:16:11 AM CDT, DougVL <k8rftradio@...> wro On Mon, Jun 19, 2023 at 01:32 PM, Stan Dye wrote:

recent firmware has a
Cable Measure function built in. Have you tried that?

It's a wonderful, very useful feature.? Very quick and easy to use, no other settings to make.
It does use a different method than TDR, and is explained in the info for the first firmware version that includes the feature. (I don't have that text available to quote here, though - sorry!)
--
Doug, K8RFT

"..cost beyond the software development." does not imply that software is free, on the contrary, it explicitly recognizes that cost.

Even a "bad and slow" SA function is better than nothing if there is no alternative. It does not need to be perfect to be useful.
73, Don N2VGU

On Mon, Jun 19, 2023 at 01:32 PM, Stan Dye wrote:

recent firmware has a
Cable Measure function built in. Have you tried that?

It's a wonderful, very useful feature. Very quick and easy to use, no other settings to make.
It does use a different method than TDR, and is explained in the info for the first firmware version that includes the feature. (I don't have that text available to quote here, though - sorry!)
--
Doug, K8RFT

The tinySA group can be found here: /g/tinysa/topics

THANKS. I signed up
--
F1AMM
Fran?ois

De la part de HA3HZ
mardi 20 juin 2023 09:14

The tinySA group can be found here: /g/tinysa/topics

--
Gyula HA3HZ ( )

On Mon, Jun 19, 2023 at 01:04 PM, Donald S Brant Jr wrote:

the extra features have no incremental cost beyond the software development.

Why do you think software development is free? However, adding a spectrum analyzer function to NanoVna is not a good idea, it will be a bad and slow analyzer with a lot of limitations.

Hello

I have never used this kind of small spectrum analyzer TinySA

- I read that there are at least 2 software on PC (like nanoVNA-saver) which allow to connect the small box TinySA. I don't want to tear my eyes out too much on a screen that's too small.

- I don't see any "groups.io" discussing this topic. Did I search wrong?
--
F1AMM
Fran?ois

Let's go back to basics and use only the basic behavior of an open and
shorted 1/4-wavelength of coax (in the cable, not physical length:

SHORTED END measures as an open
OPEN END measures as a short

With the end of your coax open, determine the frequency of the lowest short
indication. Repeat with the end of your coax shorted and determine the
lowest frequency of an open indication. The two should be very close but
take the numerical average of the two. If there is no short or open
indicated for the above tests, the coax is faulty. If there is a distinct
short/open indication, calculate the length of the coax using:

Wavelength X Frequency = speed of light (all in basic units)

This will be slightly less than the physical length as the measurements
include the velocity of propagation in the coax.

Dave - W0LEV

On Mon, Jun 19, 2023 at 2:15?PM RJOLLIS via groups.io <rjollis=
[email protected]> wrote:

Thanks for your suggestion, Stan. I will attempt to reset the sweep range
to a lower stop frequency, but it won’t happen until tomorrow.

I did make return loss and characteristic impedance measurements and they
look nominal for this coax. Zo=48.2 ohms tested at 9.8Mhz +/- 90° and the
return loss at 10Mhz is .99dB and 1.3dB at 30Mhz. Both of these figures
seem reasonable for a 100ft chunk of RG-8X. But that big spike at 14.65m
has me scratching my head. There are only minimal artifacts apparent on the
display around 120nS which you can see in my original post. So maybe there
is something hiding between sampling points.

By the way, I really love this new toy. I am trying to consume as much as
I can from the various postings, discussions and videos to be able to use
it to its fullest. What a fantastic invention! The guys who developed this
tool should get an award for one of the most useful inventions for Radio
Communications since the oscilloscope.

On Jun 19, 2023, at 1:32 PM, Stan Dye <standye@...> wrote:

?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

--

*Dave - W?LEV*


--
Dave - W?LEV

Thanks for your suggestion, Stan. I will attempt to reset the sweep range to a lower stop frequency, but it won’t happen until tomorrow.

I did make return loss and characteristic impedance measurements and they look nominal for this coax. Zo=48.2 ohms tested at 9.8Mhz +/- 90° and the return loss at 10Mhz is .99dB and 1.3dB at 30Mhz. Both of these figures seem reasonable for a 100ft chunk of RG-8X. But that big spike at 14.65m has me scratching my head. There are only minimal artifacts apparent on the display around 120nS which you can see in my original post. So maybe there is something hiding between sampling points.

By the way, I really love this new toy. I am trying to consume as much as I can from the various postings, discussions and videos to be able to use it to its fullest. What a fantastic invention! The guys who developed this tool should get an award for one of the most useful inventions for Radio Communications since the oscilloscope.

Yes 100ft Mookeef RG-8X from Amazon.

Sri? error? 73 qr0Envoyé depuis mon appareil Galaxy

Hello Robert et les amis?Je ne vous oublie pas mais impossible actuellement opération ?il gauche reprise peut être fin du mois73qro et 88 à? tous les qrasF8EZZ? joelEnvoyé depuis mon appareil Galaxy

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.