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Is there anywhere in the UK I can get an authentic version please?

Hi to all.
I had problems getting an SAA-2N using vna-saver running on windows 10, specifically it would not connect to the USB port. I solved that, and having used the vna saver on my new laptop I decided to use it in the workshop on my old Win-7 machine.

The problem is the nanovna-saver exe wont run past flashing up a dos window with what I presume is the ini files and an error message. This screen stays visible for less then a second and I came up with the idea of videoing the screen at run time to capture the image which I enclose.

Can anyone advise what program or module is missing that prevent the nanovna saver running?
My win version is 7 pro with SP1, and C++ loaded. The vna is V2_2 build time October 2020
cheers
joe

Yes, that is correct.

On Wed, Dec 8, 2021, 6:41 AM Steven Bailey via groups.io <sbailey64=
[email protected]> wrote:

Sorry Donald...somehow I conflated Donald into Doug.

Sorry Donald...somehow I conflated Donald into Doug.

Hi Doug,

So the null gain (in -DB) will not be accurate but the frequency of the null will be accurate...if I do no calibration?

Thanks,

Steve

Steven: Taking this further, if you are just looking for a return loss null, such as for tuning a magnetic loop to a given frequency, you don't even need to do any calibration, as the frequency will be accurate even if the measurement is not.
73, Don N2VGU

Thanks everyone for the great advise. I especially like the screen shots (and experiments) Roger made (thanks Roger). For my purposes (looking at antenna reflections), re-calibrating looks to not be necessary.

Steven,

For best accuracy you need to re-calibrate. This is especially true if you only have 101 data points since there will be more interpolation when you zoom.

However if you are only interested in SWR or RL the interpolation feature (on H/H4 hardware and some other models) works very well. Here is a link to some actual measurements where I "zoomed in" on a 20 m dipole.

/g/nanovna-users/topic/73210908#12926

Roger

Steven,
the 6MHZ and its surroundings from the first production may be even more interesting when the value of the cooling condenser was inadequate.
Read more on my web site.

--
Gyula HA3HZ ()

On 12/7/21 7:12 AM, Steven Bailey via groups.io wrote:

Hi all...am new to this group. Have a question about calibrating the NanoVNA. If I say calibrate from 3-30 Mhz...and then decide to look (or zoom in) at frequencies from say 5-6 Mhz...do I need to do another calibration from 5-6 Mhz?

For the standard nanovna, there's 101 points - so if you calibrate from 3-30 MHz, you have a cal point every 270 kHz.? When you zoom in, the software interpolates between those points. So over your 5-6 MHz, it will interpolate over the 7-8 points covering the range.? For the most part, it's unlikely that your VNA and connectors/cables (whatever you calibrated with) vary wildly in that range, so the results will be reasonably good.? The sort of guideline is that you don't want the *phase* of the uncalibrated reflection coefficient making a big fraction of a circle between points.

If you want better performance (or you're seeing something wonky) then recalibrating over the 5-6 MHz range gives you a calibration point every 10 kHz.

Realistically, this only makes a difference if you've got something unusual inside the calibration plane. I have been fooling with hooking up two VNAs back to back (to make all 4 measurements at once), so I have a "stub" inside the calibration plane. I'm working at low frequencies (<100 MHz), so the stub is really short.

In another experiment, I'm doing measurements with the "cal kit" connected by relays at the end of 100 ft of coax (two antennas in a phased array).? That's long enough that at higher frequencies, I get more than one wavelength in the coax, and that could make the simple linear interpolation with widely spaced points not work right.

You wouldn't have to, but the number of points it is calibrated for would
be less in the smaller range. It's best to re-calibrate and get the
benefits of all the calibration points in the new range.

Zack W9SZ

On Tue, Dec 7, 2021 at 9:14 AM Steven Bailey via groups.io <sbailey64=
[email protected]> wrote:

Hi all...am new to this group. Have a question about calibrating the
NanoVNA. If I say calibrate from 3-30 Mhz...and then decide to look (or
zoom in) at frequencies from say 5-6 Mhz...do I need to do another
calibration from 5-6 Mhz?

Hi all...am new to this group. Have a question about calibrating the NanoVNA. If I say calibrate from 3-30 Mhz...and then decide to look (or zoom in) at frequencies from say 5-6 Mhz...do I need to do another calibration from 5-6 Mhz?

Indeed it was and it seems to be giving me good measurements now with the antenna I am testing. With an antenna tuner I can get an impedance of 32 ohms at 1620 KHz which is my desired frequency. On another note, I talked with a friend of mine who is a retired RCA employee with a distinguished past and he was impressed that a piece of test equipment like this can be had for about $100 and I am impressed too. If operated with its limitations in mind this is a fantastic device especially after I flashed one of the better firmwares available in the files section.

Yes! That's the kind of thing I was trying to get you to find. That type
of mechanical issue is almost always the problem when something that was
working suddenly stops, especially after manipulating the setup, even in
innocuous ways. It's often in the least expected place.

I found the center conductor and dielectric and after putting them back in the VNA is responding correctly through out its full range. Sometimes a little poking around can solve a huge problem.

On 12/6/21 7:01 PM, Nicholas wrote:

A little embarrassing but I think I found the problem. I checked the SO-238 to BNC male adapter I was using and THE CENTER CONDUCTOR IS MISSING! It likely got lost on a piece of coax that I was using at one point. I am going to find it and put it back in. That would certainly result in an open no matter what antenna I use!

A classic problem is when someone "stretches" a piece of coax to make it reach (or when pulling through a conduit or around something else), and the center conductor pulls back within the shield, taking the center pin with it.

A little embarrassing but I think I found the problem. I checked the SO-238 to BNC male adapter I was using and THE CENTER CONDUCTOR IS MISSING! It likely got lost on a piece of coax that I was using at one point. I am going to find it and put it back in. That would certainly result in an open no matter what antenna I use!

The cable tests correctly at DC with a multimeter with the braids connected and the center conductors connected correctly. The setup I have is exactly the same as when it was working correctly but just out of curiosity, what test are you talking about that might get me closer to a solution.

When I have a problem like this, when something working suddenly stops, my
first impression would be that a connection/cable has a problem. So I
check each carefully. Sometimes a cable is broken right inside the
connector, and works fine until it is bumped; or a connector isn't reliable
when disconnected from one setup and moved to another. So I always check
those issues carefully first. Of course, I also check that the nano
input/output isn't broken by doing a simple test that I have seen work
before.
In this case you seem to have indicated (without including details) that it
gives you an 'open' indication after you changed your setup, so it could
well be that it is indeed open because of a bad cable or connection.

I calibrated it for the upper edge of the AM band, 1600 to 1700 KHz and it worked really well before with the calibration done in this range. For some reason with calibration done in the same range it is not working at all suddenly. I have never exceeded the specifications for transmitter input power being very careful about where I set that for a transmitter under test and I have followed the directions for calibration exactly including some extra steps which would be useful the ISOLAT and THRU calibration steps to be exact. It is just confusing to me why this would suddenly happen.