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Bill,

I have not heard it discussed here, but I made a little 'jig' with a series 50 ohm carbon resistor sandwiched between

a male and a female coaxial connector (made one for PL259/SO239 and N-male/bulkhead N-female).

You use your standard 246/f * Vf, but make it a little longer than you think.? Short the far end for even half-wave

multiples, leave open for 1/4 wave, 'TUNE' coax by highest return loss/lowest swr.

This is how I tune the coax for transformers (odd multiple of 1/4 wave) or feed lines for an array (even half wave).

I suppose this could be "fun" trying to do this with sma on the Nano!

73

Glen K4KV

ps - there are other iterations, by doubling or halving the target frequency...

DISlord,

Thank you so much.

Jos

Op 31-3-2020 om 21:23 schreef DiSlord:

Bill, What kind of stubs are you considering? Stubs for Z matching or simple 1/4 wave stubs for filtering or something else?

Yes, you disconnect the antenna from the cable and attach your calibration kit to the free end of the cable with the analyser at the shack end and do a single port calibration. Then reattach the antenna and make your measurements.

Knowing the coax type and length, you can use SimSmith to propagate the
measurement back to the antenna feed point.

I've offered so many emails to the SimSmith download site on this group
that I'll leave it as an exercise to the interested and motivated user to
find the link. It's easy. Just use any search engine.

Dave - W0LEV

On Tue, Mar 31, 2020 at 5:30 PM Jeff W6FCC via Groups.Io <w6fcc=
[email protected]> wrote:

Setup: I have a 40 meter dipole at 30 feet. Feeding with 100 ft of RG8X
Measurement: 7.200 Mhz, SWR at RADIO end of COAX can be measured (For the
Analysis System -- coax + antenna)

Question: Can the Reference plane be "calculated" by software. It's the
location of the antenna at the END of the Coax, discounting the Feedline,
perhaps by entering the Feedline Impedance and Velocity Factor and Loss?

Asked a different way:

Can the NanoVNA be used to isolate the antenna at the far end of the COAX
and somehow IGNORE the impact of the COAX itself ?

I realize the best way to check the antenna is AT the feedpoint, but that
is not possible right now. I'm stuck at the Radio End of the COAX and
trying to determine of the DIPOLE is too long or short.

One possible "solution" IF I could take a second piece of 100' RG8X and do
the calibration at the far end (OPEN, SHORT, LOAD) and push the Reference
plane out to the 100' mark.
But can it be done without a second piece of COAX ??

Has anyone calibrated their NanoVNA using a long piece of coax and doing
the CAL at the end of the coax before attaching to an antenna to be tested ?

Jeff, W6FCC, 3-31-2020

--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

Thanks for replying. I thought the vector network analysis would be able to adapt to the cable properties to get an accurate measure of the load at the end of the feedline.

Jeff

I make stubs on a standard bnc T f/m/f connector and use a f/f barrel in
the design, the reason being is that in the field, a wonky system swr will
electrically lengthen the stub and can be compensated by using a bnc f/f/f
gendered T and removing the barrel, assuming you planned ahead and brought
everything.

Or you could always find a trombone player.

The other cabling shouldn't act like a stub: I don't worry about it.

You can only measure the actual antenna impedance remote from the antenna, with a 1/2 wavelenght of coax or feedline (x the velocity factor of the feedline), measured at a single frequency of interest.

If you are going to use a multi-band antenna, you particularly want to measure the impedance at the coax input point in order to know what the transmitter will be actually looking at, as a function of the antenna/feedline system.
Ray,
W4BYG

--
This email has been checked for viruses by AVG.

Carey,

If the antenna is NOT 50 ohms (it's actually an offset multi-band dipole with a 4::1 balun transformer), or not resonant, I was thinking that the COAX would introduce some problems.
They do use small runs of COAX for matching, that's what I was thinking, that the SWR would not be constant across the length of the COAX if the antenna was not 50 ohms resonant.

I was looking for a way to put the imaginary connector to the antenna at the far end of the COAX but maybe that's not going to solve anything.

Jeff

For additional undestand how it work:

You can use generator, set freq for example 20Mhz, set AM modulation 60% and freq 1kHz
Output for example 100mV

Connect to NanoVNA CH1

Set on NanoVNA center freq 20MHz, and span 5kHz, and CH1 Logmag
Now you can see AM signal spectre on you NanoVNA

You can change bandwidth setting and see changes (its like VBW option on any spectrum analyser), less BW freq allow recive less noise and better measure signal data, but need made more measures

DiSlord wrote:
bandwidth N

N - is number from 0 to 255 (not reccomend use values bigger then 99, possibly counter overflow)

N+1 number of samples count passed in dsp
One sample process give 1kHz bandwidth
Two samples give 500Hz
100 samples give 10Hz

BW = 1000 / (N+1) Hz
==============================================

Additionally, for the information of other group members, sending the bandwidth command without any qualifier returns the current bandwidth, i.e.:
sending:
bandwidth
returns
bandwidth 0 (1000Hz)

From the DISPLAY-BANDWIDTH menu only 5 bandwidths are selectible:

1 kHz, 300 Hz, 100 Hz, 30 Hz, 10 Hz

- Herb

bandwidth N

N - is number from 0 to 255 (not reccomend use values bigger then 99, possibly counter overflow)

N+1 number of samples count passed in dsp
One sample process give 1kHz bandwidth
Two samples give 500Hz
100 samples give 10Hz

BW = 1000 / (N+1) Hz

Has anyone used the nanovna to make tunes coaxial stubs? I was thinking you'd need to get rid of the jumper which would add length to the overall stub. I picked up an SMA to SO-239 connector which hopefully would do away with the extra cable.
Anyone have any tips for this?
Thanks
Bill K4FX

HI DiSlord,

Thanks very much for the great firmware, it runs fine on my -H4. Can you tell me please the syntax of the bandwith command ?

Thank you,

Jos

Op 31-3-2020 om 00:15 schreef DiSlord:

Just a note for we nit pickers. RESISTANCE is not frequency independent. For example, in transmission lines the skit effect and dielectric losses, affect the resistance. Related effects can be found in inductors and capacitors.....

The coax, unless it's defective, only adds loss (and rotation around the
Smith Chart) to the measurement of the antenna. It doesn't affect the
frequency response.

You could calibrate S11 with the coax connected and applying Short, Open,
Load at the far end of the coax with the antenna disconnected.

Or, just measure it as is - the Return Loss dips will be at the same
frequency as if you measured directly at the antenna. Just the depths of
the dips will be different.

Make sense?

73, Carey, WB4HXE


On Tue, Mar 31, 2020 at 1:30 PM Jeff W6FCC via Groups.Io <w6fcc=
[email protected]> wrote:

Setup: I have a 40 meter dipole at 30 feet. Feeding with 100 ft of RG8X
Measurement: 7.200 Mhz, SWR at RADIO end of COAX can be measured (For the
Analysis System -- coax + antenna)

Question: Can the Reference plane be "calculated" by software. It's the
location of the antenna at the END of the Coax, discounting the Feedline,
perhaps by entering the Feedline Impedance and Velocity Factor and Loss?

Asked a different way:

Can the NanoVNA be used to isolate the antenna at the far end of the COAX
and somehow IGNORE the impact of the COAX itself ?

I realize the best way to check the antenna is AT the feedpoint, but that
is not possible right now. I'm stuck at the Radio End of the COAX and
trying to determine of the DIPOLE is too long or short.

One possible "solution" IF I could take a second piece of 100' RG8X and do
the calibration at the far end (OPEN, SHORT, LOAD) and push the Reference
plane out to the 100' mark.
But can it be done without a second piece of COAX ??

Has anyone calibrated their NanoVNA using a long piece of coax and doing
the CAL at the end of the coax before attaching to an antenna to be tested ?

Jeff, W6FCC, 3-31-2020

--
Carey Fisher
careyfisher@...

Setup: I have a 40 meter dipole at 30 feet. Feeding with 100 ft of RG8X
Measurement: 7.200 Mhz, SWR at RADIO end of COAX can be measured (For the Analysis System -- coax + antenna)

Question: Can the Reference plane be "calculated" by software. It's the location of the antenna at the END of the Coax, discounting the Feedline, perhaps by entering the Feedline Impedance and Velocity Factor and Loss?

Asked a different way:

Can the NanoVNA be used to isolate the antenna at the far end of the COAX and somehow IGNORE the impact of the COAX itself ?

I realize the best way to check the antenna is AT the feedpoint, but that is not possible right now. I'm stuck at the Radio End of the COAX and trying to determine of the DIPOLE is too long or short.

One possible "solution" IF I could take a second piece of 100' RG8X and do the calibration at the far end (OPEN, SHORT, LOAD) and push the Reference plane out to the 100' mark.
But can it be done without a second piece of COAX ??

Has anyone calibrated their NanoVNA using a long piece of coax and doing the CAL at the end of the coax before attaching to an antenna to be tested ?

Jeff, W6FCC, 3-31-2020

-F

Stay virus safe & follow the rules!

Cheers,
Marty Hadfield

On Mar 31, 2020, at 9:38 AM, Larry Rothman <nlroth@...> wrote:

? Welcome to the forum.
What model did you buy? There are 4 models: original, -H, -H4, or -F?

On Tuesday, March 31, 2020, 11:52:24 a.m. GMT-4, Andrew Steen <k6stn.1@...> wrote:

Hello. I am new to the group, having just received my new nanovna yesterday. At first, it was working great with the nanovna saver program. Then, it only shows a light blue screen. No display at all. Anyway to recover, or do I need to replace the unit?
Thanks,
Andrew

Would whoever admins the Wiki put all these links

.. all >>what<< links?

in a conspicuous space

Is this sufficiently conspicuous?
/g/nanovna-users/wiki/External-links#Smith-charts-and-Touchstone-28S1p2C-S2p29-files

Without reviewing them personally, I am likely to add only those specifically rated better than those already linked.

Thanks for all the great advice.
I did pull the usb cable and it powered on with the normal screen.
I had been using it on the desktop, and assumed it was charged.
I now have it on a regular 5v charger, so that should fix the issue.
Again, thanks to all for your great advice on this issue.
Andrew