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I've been thinking about purchasing a VNA. I mainly will need it for HF and VHF and I will only be using it once in a while for tuning a few antennas I have in my attic.

I have been looking on Amazon and eBay and saw so many versions and also so many different prices.

Saw V2, V4.3 and SA, H4 ? Its really been overwhelming. !

Any ideas on which one would be best for me ?

Frank

Hi,

I don't know whether or not this applicable, but I was having a very strange display.? I put the NanoVNA in CW mode and noticed the output was low (~-50dBm).? I replaced the SI5351 and that cured the low output problem, but the unit was still not operating properly. I replace all three SA612's and still no luck.? I did not have any output on CLK2 of the SI5351, so I replaced it again, and that fixed the problem. The SI5351 lead spacing is tight, so I may not have had the first one installed correctly.

Tom?? W0IVJ

Jerry,
On most NanoVNA models, the shields are removable without desoldering. They have little surface-mount clips to hold them in place. A good magnifier is helpful.
--John Gord

I took the cover off today. The SMA connector is solidly soldered to the top of the board. However, it also looks like its pins go through the board and may be soldered on the back side. But there's a shield over that side part so I can't see if that is soldered or not. Can anyone tell me if the connector is soldered on the back side of the board or not? I hesitate to takeoff the shield unless I absolutely have to.

TIA es 73,
Jerry, AI0K

Hi, Jim,

Yes, that's always possible even though I've been very careful in inserting into the jack - to the point I even use a female-male SMA adapter to protect the one on the NanoVNA. But that's no assurance I didn't screw up installing the adapter, either - just that I only do it once when I get the NanoVNA out instead of multiple different connectors.

Hi again, Dave,

That's possible with the pigtails I have but I would think the open/short/load connectors that came with the device would work. Of course, there's always the other problem that one of the connectors i got is larger and has spread the center conductor hole. It doesn't look like that happened, but it's so hard to tell on these small connectors.

In any case I'm going to take the case apart tonight and see what it looks like on the board. If it is the connector I don't know what to do about it.

Thanks es 73,
Jerry, AI0K

On 10/17/22 12:58 PM, W0LEV wrote:

It may be a "rocking" SMA connector on the board. However, another problem
I've experienced with connectors and adaptors from China is tolerance on
the center pin. I've run into the situation where the center pin has too
small of a radius / diameter to properly mate with the mating connector.
Rock it back and forth and look for discontinuous changes in the data.

+1

It could be either the jack (center hole is a bit too big)
or the pin (too small).
You can get the former by not being careful when mating (at a bit of an angle) or if the center conductor is rotated).

It may be a "rocking" SMA connector on the board. However, another problem
I've experienced with connectors and adaptors from China is tolerance on
the center pin. I've run into the situation where the center pin has too
small of a radius / diameter to properly mate with the mating connector.
Rock it back and forth and look for discontinuous changes in the data.

Dave - W?LEV

On Mon, Oct 17, 2022 at 6:19 PM Jerry Stuckle <jerry@...>
wrote:

Mike,

Thanks. Great thought - but I'm trying to measure a J-Pole so it has 0
ohms DC resistance between center conductor and shield.

Some new information. I played some with it again this morning. When I
first tried it with everything connected directly to the S11 connector it
worked fine on both bands. gave me the results I expected. Adding the
pigtail worked on 2 meters but not 440. Then it failed on 2 meters also,
both with and without the pigtail.

I'm beginning to think perhaps the SMA connector is making intermittent
contact with the board. I'll take it apart later and take a look but I'm
not sure my eyesight will allow me to fix it.

73 es tnx agn
Jerry, AI0K

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


--
Dave - W?LEV

Mike,

Thanks. Great thought - but I'm trying to measure a J-Pole so it has 0 ohms DC resistance between center conductor and shield.

Some new information. I played some with it again this morning. When I first tried it with everything connected directly to the S11 connector it worked fine on both bands. gave me the results I expected. Adding the pigtail worked on 2 meters but not 440. Then it failed on 2 meters also, both with and without the pigtail.

I'm beginning to think perhaps the SMA connector is making intermittent contact with the board. I'll take it apart later and take a look but I'm not sure my eyesight will allow me to fix it.

73 es tnx agn
Jerry, AI0K

Hi Jerry, did you short out the antenna prior to connecting the Nano ? Static buildup will destroy the front end of the Nano. Just a thought.

73 Mike N7ATC

Arie,

Thanks for the response. Yes, I've had this for a while but used it little. I don't guarantee the problem here isn't between the ears :)

I thought about bad connections but unless it's the S11 port itself I don't see a problem. I normally use an SMA male-female adapter to protect the one on the Nano. Since I use a 6" cable to adapt the SMA male to SO-239, I use another 6" cable with SMA male and female to calibrate.

These came up with weird readings like in my images so I went back to basics - I plugged the calibration units directly into the S11 jack. That is what you see here.

I'm afraid I might have blown the front end of the Nano but I don't know what would have done it. It's been a case in the house since I last used it (and it worked perfectly). I could try flashing the firmware again but I don't think it would help.

The biggest problem is that while I have the technical expertise to dig into it, at 70 years my eyes are too old to work on SMT, even with a magnifying glass.

73,
Jerry, AI0K

Hi Jerry,

If you own the nano for a long time, you probably know the ropes and tricks of calabration and such.

If I would have the readings you show here, I would suspect a loose connection or some dirt here and there. The readings you are showing are random values.

First thing I'd do is clean all connectors, check coax is involved, and calibrate again en see what happens. After the calibration on the nano, i would connect the open, closed and 50 ohm as is I were calibrating and then check the smith chart.

73

Arie PA3A

Op 17-10-2022 om 01:30 schreef Jerry Stuckle:

Dave,

Thanks but I did the cal on the unit, not the laptop. And the results on the unit are very similar to that on the laptop.

Sorry I wasn't more clear on the process. Mea culpa.

Jerry, Ai0K

The cal done on the native instrument is not used when you employ Saver on
the PC or laptop. However, once you run the cal. using SAVER, you can
store it on the PC or laptop for future use. The cal. files are not common
between the native instrument and PC supported firmware. If you use SAVER,
you need to cal. in Saver (and save the results on the PC for future use).
The cal. routine built into SAVER is quite useful and intuitive to use.

Dave - W?LEV

On Sun, Oct 16, 2022 at 11:30 PM Jerry Stuckle <jerry@...>
wrote:

Hi, all,

I've had a NanoVHA-H4 for about a year and a half now but haven't used it
that much so this could easily be a problem between the ears.

I used it a couple of months ago to check a couple of HF antennas and it
worked fine It's been sitting since then in my shack. Today I went to
check a VHF/UHF J-Pole but didn't even get past the calibration.

I clicked on reset to reset the calibration. I then used open/short/load
to calibrate 143-149 MHz and 435-455MHz, storing in positions 1 and 2,
respectively. When I used the latest version of Nanpvna-Saver I got bad
results, so I went back to the basics. Even the 50 ohm load gave bad
results (the display on the VNA showed similar results so it isn't they
Python program). The Smith Chart and VSWR plot are attached. Please
remember - this is with the 50 ohm load attached directly to CH0 (S11) on
the VNA and calibrated (correctly - I think) to the frequencies involved.
The 2 meter scan is from 144--148 Mhz and 3/4 meter scan from 440-450Mhz.

Does anyone have any ideas on what might be wrong? Considering the
problem may be between the Nano VNA and the chair...

Thanks,
Jerry, AI0K

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


--
Dave - W?LEV

I should also add both the Nano VNA and Nanovna Saver are at the latest versions and it all worked fine with the same antenna last spring. Just trying to tune it a bit closer to optimum before winter sets in.

Hi, all,

I've had a NanoVHA-H4 for about a year and a half now but haven't used it that much so this could easily be a problem between the ears.

I used it a couple of months ago to check a couple of HF antennas and it worked fine It's been sitting since then in my shack. Today I went to check a VHF/UHF J-Pole but didn't even get past the calibration.

I clicked on reset to reset the calibration. I then used open/short/load to calibrate 143-149 MHz and 435-455MHz, storing in positions 1 and 2, respectively. When I used the latest version of Nanpvna-Saver I got bad results, so I went back to the basics. Even the 50 ohm load gave bad results (the display on the VNA showed similar results so it isn't they Python program). The Smith Chart and VSWR plot are attached. Please remember - this is with the 50 ohm load attached directly to CH0 (S11) on the VNA and calibrated (correctly - I think) to the frequencies involved. The 2 meter scan is from 144--148 Mhz and 3/4 meter scan from 440-450Mhz.

Does anyone have any ideas on what might be wrong? Considering the problem may be between the Nano VNA and the chair...

Thanks,
Jerry, AI0K

Hi John,
I noticed you joined the forum September 1st.

Please look over the forum's Wiki for lots of information on using the NanoVNA.
You'll note that the very first item in the forum is a note on how to search forum messages. There is a wealth of information that has been contributed by various members and many questions posed by new members have already been answered.

Grab a copy of the Absolute Beginner's Guide document in the Files area of the group.

Cheers
... Larry

On Sun, Oct 16, 2022 at 02:43 PM, Ho-Ro wrote:

Sorry, ignore my bin and hex links, they are for the -H. Older devices do not
have the SD card slot. Just follow my other hint and do:
NANOVNA_F303=1 make
and flash the bin file ch/*.bin

This works only on my linux system, but here are the current binaries build from DiSlord's source:

It's probably not worth putting too much effort into the curve fitting algorithm below a few MHz because I think this is the region where the dielectric losses can begin to cause an increase in ESR with reducing frequency. Starting up at VHF and working downwards, the ESR of a ceramic cap typically falls with reducing frequency due to reduced metal losses but at some point, the dielectric losses cause it to start climbing up as the frequency is reduced. I'm not sure where this happens with a porcelain cap like the ATC 800B. In my experience the ESR of the 800B caps can still be seen to be falling down towards 10MHz but I'm not sure where the ESR will eventually start to climb again.

To amplify on my previous post, one application I have is routinely tuning an HF screwdriver antenna which I use on 80-10m. For this purpose, I so one 401 point calibration over that entire range, and then have set up and saved higher resolution scans (using that single calibration) over each of the relevant segments of the ham bands. I can recall a scan setup, tune the screwdriver to achieve the lowest SWR at the desired frequency, and when I switch to transmit, I get essentially the same SWR indication on my transceiver and the external SWR meter. Prior to using the nanoVNAPlus4, I used my venerable MFJ259B, which is ~22 years old now and has never been re-calibrated since it was new. I can still use that and compare what I get with the nanoVNA. They agree pretty well, to maybe a couple of tenths. Of course I can also compare or check either using a few dummies (and SOLT loads) I've created for the purpose.

This is a simple HF application. Depending on what your doing, particularly in UHF and above, things can be more sensitive.