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In addition, the newly released NanoVNA-H reduced the RG174 cable from 30cm to 20cm to reduce the loss. If I make a VNA with a frequency higher than 1GHz, I will use the RG316 cable. On large VNAs in the lab, it is common to use RG402 cables.
This is the cable parameter provided by China's cable manufacturer：


hugen

Hi,
Thanks for the answer, I didn't expect to get a lab weighing station :-)
Only a few days that see, the duality on the cable labeled it.
Its mechanical size is closer to 1.5C-2V.
One question for the knowledgeable:
what is the length of a measuring cable, which is also a calibration cable?
The TAPR has 1m and 3m in the description and 30cm ... 60cm elsewhere.
I understand that quality has to be paid for, I am looking for a compromise.
Thank you for replying.

Hi,

The reading results are similar between RF Vector Impedance Network Analyzer N1201SA and the
nanoVNA/nanoVNAv1.03b4.1 during Mobile Antenna SWR testing. The length of the RG-58 coaxial
cable of the mobile antenna is also measured with the TDR and the result is also almost equal with
its actual length at 2.98 m.

Kind regards,

neb

Yes, some manufacturers also provide 75 ohm RG174 cable. The RG174 cable provided by NanoVNA-H is 50 ohm. I have checked the parameters of RG174 and RG316 cables. They are not ideal at 1 GHz. Obviously it would be better to use RG405 or RG142, but they are too hard and not suitable for portable devices. If you use it in the lab, I recommend using RG405 or RG142 cable.

hugen

On Thu, Oct 10, 2019 at 11:03 AM, Gyula Molnar wrote:

RG174A/U is actually 50 Ohm.

You cannot believe marking, this is just some noname cable with any marking on it :)

The cable that I got with NanoVNA is marked just as "RG174 ROHS". But it has some high mismatch, because I measure it with dummy load at the end it has high waves, VSWR varies from 1.00 to 1.14.

When I do the same with RG405, there is no waves, VSWR is straight line with VSWR=1.01.

So, it looks, like this "RG174" is really 75 ohm. It explains why it works bad :)

If you measure Z11 using S11 then the Q is given by fc/ BW where BW is taken between |Z|/Sqrt(2) points on your frequency plot. Or alternatively taken between +/- 45 degrees on the phase plot.

On Thu, Oct 10, 2019 at 10:50 AM, <hugen@...> wrote:

You should calibrate at the end of the cable and the difference in the picture
measurements you show is caused by the cable length, not the cable quality.

You're right in order to compare S11, there is need to perform OSL through cable.
See measurement in attachment.
Now rg174 looks almost the same, but still has worse performance. :)

Hugen, if you don't believe the caption, then it's really 50 Ohm from another manufacturer, but for Chinese it's 75 Ohm.
See CABLE & WIRE.pdf at
or

Might the cable manufacturer mistakenly solder it?

RG174A/U is actually 50 Ohm.

On Thu, Oct 10, 2019 at 02:55 PM, <qrp.ddc@...> wrote:

On Thu, Oct 10, 2019 at 03:17 AM, Kurt Poulsen wrote:

Wrong, the cables are part of the NanoVNA hardware and cancelled out during

calibration.

That's Wrong. You cannot cancel bad cable effect with calibration. You can
only reduce it for a little.

For example, here is calibration+measurement performed with rg174 32 cm (which
come with NanoVNA) and with rg405 10 cm. See attachment.

The test cases are following:
1) perform calibration with rg174
2) measure rg174

1) perform calibration with rg405
2) measure rg405

If it were possible to eliminate bad cable effect (as you mentioned), both
measurement will be exactly the same. But they are different, and rg174 are
much worse.

You should calibrate at the end of the cable and the difference in the picture measurements you show is caused by the cable length, not the cable quality.

On Thu, Oct 10, 2019 at 03:22 PM, Gyula Molnar wrote:

Hello

I also got the nano with a RG174 cable, which according to the label and the
datasheets is 75 ohms.
Thus, 75 Ohm and 50 Ohm cables are compared. Oooops

Hello

I also got the nano with a RG174 cable, which according to the label and the datasheets is 75 ohms.
Thus, 75 Ohm and 50 Ohm cables are compared. Oooops

measurements for rg174 and rg405

On Thu, Oct 10, 2019 at 03:17 AM, Kurt Poulsen wrote:

Wrong, the cables are part of the NanoVNA hardware and cancelled out during calibration.

That's Wrong. You cannot cancel bad cable effect with calibration. You can only reduce it for a little.

For example, here is calibration+measurement performed with rg174 32 cm (which come with NanoVNA) and with rg405 10 cm. See attachment.

The test cases are following:
1) perform calibration with rg174
2) measure rg174

1) perform calibration with rg405
2) measure rg405

If it were possible to eliminate bad cable effect (as you mentioned), both measurement will be exactly the same. But they are different, and rg174 are much worse.

I have noticed the feedback that the newly sent NanoVNA-H sma F-F terminal will be replaced with tetrafluoroethylene.

hugen

On Thu, 10 Oct 2019 at 06:25, johncharlesgord via Groups.Io <johngord=
[email protected]> wrote:

A photo of the dissected barrel connector is at:

/g/nanovna-users/album?id=96185

--John Gord

Em, enough said, I initially thought that the melted stuff was hot-melt
glue. That might have worked better as a dielectric!
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

Yes there is a Facebook Group “NanoVNA” but be careful you could be blocked or band without warning lol. I really have to just laugh at these admins. Acting like kids. I guess they are affiliated with Gigaparts that’s why I caned. LoL.

A photo of the dissected barrel connector is at:

/g/nanovna-users/album?id=96185

--John Gord

On Wed, 9 Oct 2019 at 13:04, <erik@...> wrote:

There is some asymmetry in some barrel connectors causing problems if the
male pins are also a bit different. If I reverse the barrel connector there
is no connection with the LOAD, the other way around it works....

Which basically results in the same conclusion that the adapter is only fit
for bin. ??????



--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

On Thu, 10 Oct 2019 at 01:17, Kurt Poulsen <kurt@...> wrote:

Hi qrp.ddc
Wrong, the cables are part of the NanoVNA hardware and cancelled out
during calibration.
The may cause phase changes when bended during practical measurements
Kind regards
Kurt

I have not extensively tested the cables supplied with my NanoVNAs, but
giving *one* cable 20 seconds to relax after bending, shows the reflected
signal not changing any more than -35 dB up to 1.5 GHz. That is reasonable.
Maybe if one tugged on the cable a bit, which could easily happy in
practical measurements, things would get poorer. This really was based on a
test taking one minute, so hardly conclusive.

In contrast, a test taking one minute showed me the adapter is very poor.


I can’t imagine myself wanting to use SMA connectors much with the NanoVNA,
as I want it for antennas measurements outside - I have better instruments
available for lab use. But if I did use the NanoVNA in a lab
environment, *based
on the smallest possible sample of tests*, I would not be overly concerned
about the cables.

Anyone can easily test the cables using the NanoVNA. You don’t need
expensive lab equipment to test them.

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

Some people reporting that they have measurement issues at low frequency with white "lizard" version.

Also, it seems that Chinese manufacturers prepare firmware to support low quality element by reducing working range of frequencies. So, there is needs to be careful. Cheap NanoVNA may be just a factory rejected boards with a bad quality components and 800 MHz firmware.