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I reported a few days ago that I had measured the return loss of one of the
female-female thrus supplied with my NanoVNAs when open at one end.
Measurements were made with an HP 8720D VNA with an HP 85052B calibration
kit. The return loss was 0.368 dB at 1.5 GHz, which is much higher than
the 0.05 dB or less I was expecting.

Kurt Poulsen had discovered much the same using his HP 85033C calibration
kit with the VNWA.

Today I was busy, but whilst I had a spare moment I put one of the
connector guages from my Maury Microwave SMA connector guage kit on the
female-female thru. This his 4 guages and can check

* Male pin
* Male dielectric
* Female pin
* Female dielectric

I can’t recall what guage I picked up - it might have been for the pin or
it might have been for the dielectric. I can check again when I have some
time.

Anyway, both ends of the thru were mechanically out of specification. The
pin (or might have been dielectric) is protruding too far forward. The
amounts were quite small - one end 0.0005” and the other end 0.003”. But
the should *never* be precessed, as it can damage connectors you mate to.
There should always be some recession, but it should be as small as
possible. Recession on SMAs is typically 0.01”. This allows for
manufacturing tolerances to ensure there’s no precession, which can damage
other connectors.

Anyway, just something else to be aware of. Not only is the thru
electrically poor, but it’s mechanical properties are such that it has the
potential to damage connectors you mate it to.

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

While not an expert on this I check my SWR at the antenna to take the cable out of the equation.? After adjusting the antenna I add the cable to the test to see what the addition of the cable does to the system.? Based on that I work to get the lowest SWR for the system.? That being said I would calibrate the VNA using none for at the most a very short cable.
John GalwayKH6JTE

Am I missing something big here? Does this nanovna calibrate the end of the cable as the reference plane? All VNAs should do this. Mine does not. Recalling cal 0, with the TX connector open, it looks like an open. If I do a complete calibration at the end of the cable, then leave it open at the end, it is not an open, at any frequency. What am I doing wrong?

On Thu, 10 Oct 2019 at 17:42, Larry Rothman <nlroth@...> wrote:

Why not make the impedance a selected item in the firmware with a default
to 50 but allow manual input within a fixed range?

Yes. I did mean that to be detault behave, despite what I wrote would not
have achieved that

On Thursday, October 10, 2019, 12:33:05 p.m. GMT-4, Dr. David Kirkby
from Kirkby Microwave Ltd <drkirkby@...> wrote:

On Thu, 10 Oct 2019 at 03:24, S Johnson <cascadianroot@...> wrote:

So it would be nice if all references to 50 ohm removed from the firmware.

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

Hi,

I have compared SWR measurements between my NanoVNA and a RigExpert AA-600.
Small SWR measures somehow seem to look much better on the NanoVNA.

An Antenna that on the RigExpert had SWR 1: 1.38 just had 1 : 1.18 on the
NanoVNA.

It probably has to do with the smaller measuring voltage of the NanoVNA and
limited
low signal diode detection possibilities.

The low values on the NanoVNA are the less accurate ones, of course.

Hans, DJ7BA



--
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Hi Carlos
Great, very assuring. Agree photos is a good idea and I did that some time ago when I started to comment this topic.
One of these days I will issue a document when to use male and female kit for insertable and non-insertable DUT's. It is quite easy to make mistakes regarding calibration and ensuring calibration is at the calibration plane and not out in the blue air or somewhere inside the test cables.
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af Carlos Cabezas
Sendt: 10. oktober 2019 17:13
Til: [email protected]
Emne: Re: [nanovna-users] Clabraion kir data for both the male and female kit

Hi Kurt,

I made the same measurement on my nanoVNA cal kit. Got 22e-15 too for C0. See /g/nanovna-users/message/4526

However i know different kits are being supplied. A friend got a low quality short made in a single piece that leaves a small air gap. So we must attach kit photos with the obtained coefs. I need to get a good macro camera...

Carlos

Or simply export the NanoVNA sweep files and import them in SimSmith.
There you have grahic Q lines - and much, much more: All you possibly may want.

Hans, DJ7BA

-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von alan victor
Gesendet: Donnerstag, 10. Oktober 2019 17:44
An: [email protected]
Betreff: Re: [nanovna-users] Measuring Q

ditto, Yes Jeff.

I would like to see the derivation.

Need to find the text. The Q=1/BW, huh?

It is interesting to note, folks have made an academic career in studying Q and how to measure it.
And another group have made another career on studying antenna and related Q of an antenna to that of the classic R-L-C network. In another words, these subjects are not trivial.

Measurement of Q on the network analyzer, also not trivial.

The most straightforward method was to add a Q template over the Smith Chart. The template had a pair of arcs drawn that connected all R=jX, R=-jX reactance values together. Then observe the intersection of the CIRCLE swept resonance contour of the reflection coefficient and the two-frequency points of intersection. This provides the BW and the zero crossing of the resonance circle contour, fo.

If it is available on line see hp application note 117-1.




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Checking is better than assuming 'new = ok'.

My 50 Ohm SMA load that came with my NanoVNA was open from the beginning.
The double female SMA barrel on one side didn't screw all the way, just 2 threads.
I got a small refunding, but I had to wait for the replacement from two other Companies,
where I bought (to be on the safe side) two ea. new ones, as the NanoVNA seller didn't
have any spares. The two new loads bought together differ (measured by DC Ohm-meter)
by > 1 Ohm.

But what shall I say for some 50 $ total price? No issue.

DJ7BA

-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von RW3ACQ via Groups.Io
Gesendet: Donnerstag, 10. Oktober 2019 19:02
An: [email protected]
Betreff: Re: [nanovna-users] Very poor thru (barrel) supplied with NanoVNAs

Hi dear all! I'm new to the forum, I didn't manage to start a new topic, but today my SMA 50 Ohm load stopped working. It worked yesterday when I received my NanoVNA, but today it does not. All the cables/wires and inputs are double-checked with another load made of PL-259 and 51 Ohm DIP-resistor. Surprising but true.




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Hi. I too purchased the testboard. Was wondering if you easily soldered to the pcb pads? What solder/flux did you use? I am having difficulty wetting the pads. The sma sockets weren't a problem. I didn't clean the pads before starting but I sure used a lot of flux after. Sorry for the interruption. Thanks 73 Ray ae5hn

Considering the cost of a nanoVNA, I wonder if anyone sells these parts.? I worry about the same thing happening to me.
I do have a cal kit from an old VNA I could use, with the proper adapters to get to type N.? And I have a Tektronix BNC through termination that would suffice for most frequencies.
Bob

Hi dear all! I'm new to the forum, I didn't manage to start a new topic, but today my SMA 50 Ohm load stopped working. It worked yesterday when I received my NanoVNA, but today it does not. All the cables/wires and inputs are double-checked with another load made of PL-259 and 51 Ohm DIP-resistor. Surprising but true.

On Thu, 10 Oct 2019 at 02:41, Pierre Martel <petem001@...> wrote:

There is a facebook group?

If it is true, thats about the best thing to lower the noise floor in this
group. Just send noobs there and let the childish admin deal with it ;-)

That is effectively saying one should send novices to a place with childish
admins.

I believe the traffic here is too high and should be reduced. But your
suggestion doesn’t seem a good way to achieve that.

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

Why not make the impedance a selected item in the firmware with a default to 50 but allow manual input within a fixed range?

On Thu, 10 Oct 2019 at 03:24, S Johnson <cascadianroot@...> wrote:

I’m guessing that with a 75-ohm calibration it might be.

Whilst I accept 75 ohms is the 2nd most common impedance after 50 ohms, it
would be nice if *any* impedance could be a supported. The bridge itself is
50 ohms, but there are two ways around this

1) Minimum loss pads can be used to allow calibration with 75 ohm
calibration kits. There are 75 ohm versions of both N and BNC connectors,
and calibration kits for both available. The F connector is only 75 ohms
and calibration kits for F - my company has both mechanical and electronic
kits for F.

2) One may wish to calibrate with a 50 calibration kit, but have all S
parameters showed compared some other impedance. For example, I have an
application where it would be nice to have 112 ohms in the centre of the
Smith Chart.

3) Whilst I admit it is a bit unlucky that waveguide would be used with a
NanoVNA, it is not totally impossible. I have seen waveguide suitable for
450 MHz for a professional application. It seems standard practice to
configure the VNA for 1 ohm in that case.

So it would be nice if all references to 50 ohm removed from the firmware.

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

ditto, Yes Jeff.

I would like to see the derivation.

Need to find the text. The Q=1/BW, huh?

It is interesting to note, folks have made an academic career in studying Q and how to measure it.
And another group have made another career on studying antenna and related Q of an antenna to that of the classic R-L-C network. In another words, these subjects are not trivial.

Measurement of Q on the network analyzer, also not trivial.

The most straightforward method was to add a Q template over the Smith Chart. The template had a pair of arcs drawn that connected all R=jX, R=-jX reactance values together. Then observe the intersection of the CIRCLE swept resonance contour of the reflection coefficient and the two-frequency points of intersection. This provides the BW and the zero crossing of the resonance circle contour, fo.

If it is available on line see hp application note 117-1.

Cool, thanks!

Hello,

This email message is a notification to let you know that the following files have been uploaded to the Files area of the [email protected] group.

• /Firmware/75 Ohm Firmware.zip

Uploaded By: Larry Rothman <nlroth@...>

Description:
This is the 75 Ohm firmware (Aug-30-19) and instructions from Xenomorph on the Russian http://www.cqham.ru NanoVNA forum. Forum link is in the PDF in the zip. Please ask Xenomorph for support on his custom firmware. Use Chrome in translate mode to view the Russian website.

Cheers,
The Groups.io Team

Hi Kurt,

I made the same measurement on my nanoVNA cal kit. Got 22e-15 too for C0. See /g/nanovna-users/message/4526

However i know different kits are being supplied. A friend got a low quality short made in a single piece that leaves a small air gap. So we must attach kit photos with the obtained coefs. I need to get a good macro camera...

Carlos

To my knowledge, Xenomorph is the only one who has created a firmware version for testing 75 ohm systems.
I will place a file containing his firmware and instructions in the Firmware folder on this forum.
Regards,
Larry

I would not waste my time with these questionable connectors and cables. I am use Amphenol adapters, SDR-Kits Calibration kits and quality SMA cables that I rescued from scrap HP test equipment.

Mike N2MS