开云体育

Hi,
I am facing similar in fact worst situation. Just using the same coaxial cable you showed in your picture and connecting to its end a 20 cm bare copper wire (that I am planning to use as an antenna) to measure its impedance, or even connecting this bare copper wire directly to CH0 through an SMA connector. Moving my hand around the nanoVNA, and trying to tap on the LCD changes significantly the readings on the nanoVNA. My nanoVNA has no shielding inside it. So, may be this is making things worst.

Seems from the replies that this an expected behavior, and I should connect the antenna under test through a long cable to keep it away from the nanoVNA.

With the antenna that close to the VNA, ferrites are a must at both ends of
the connecting coax. Install ferrites and move the antenna structure
several wavelengths away from the VNA.

Also, for an instrument like this, the antenna is far too close to the
VNA. We know early models indicated additional shielding was required.
This is not a piece of HP/Agilent/Keysite test gear. Even the 8753C
exhibits this problem to a much lesser extend when I measure antennas at
the H1 frequency, 1.420 GHz.

A vertical monopole must be perpendicular to the ground plane. In the
first picture, it appears the vertical radiator is in the plane of the
ground plane. It should be perpendicular to that plane. It is the ground
plane perpendicular to the monopole that renders it an unbalanced
source/load - coaxial feed.

Dave - W?LEV

--

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

A better picture would help. Seems like your ground plane is tiny compared to the radiating part. And its hard to see but it looks like your ground plane is parallel to you radiating element.

Both those things are making you test equipment part of the antenna.

Dave
VE7HR

Looks like your feedline is radiating and your USB connection becomes part of the antenna. Try using ferrites over the outside of the RF cable right at the antenna to decouple your cable.

The email is K2RMA <at> arrl.net

73s

Marco

Hi,
I try to use NanaoVNA for measuring a vertical ground-plane antenna at 170MHz for later impedance matching.
A picture of the test setup is attached.
Connecting NanaoVNA to USB affects the measurement quite much, as you can see on the pics (max scale for VSWR here is 10).
Does anybody made the same experiences, as I never read about this being a problem?

The NanaoVNA has been calibrated with the same wire, as attached to the antenna and all calibration points (open, close, load) show the same values on the display, no matter if USB is connected or not. But attached to the antenna, the measurement shows quite different results.
And I'm not really sure if the results are reliable, even with unconnected USB.
The antenna should physically (length of the whip) have an VSWR minimum at 170MHz and not a peak (USB not connected).
Connected to USB, the result makes more sense to me, but I don't know which result to trust.
Any ideas what I'm missing or what I can do?

I have two NanoVNA devices from different suppliers, which both show the same results.

Many thanks!

On Fri, 29 Nov 2019 at 12:30, Dejan Corovic via Groups.Io <Dejan.Corovic=
[email protected]> wrote:

Agreed.

So is there a seller on UK eBay or Amazon that you bought before and he
wasn't selling fakes?

If you intend using the unit without a PC attached, I would get one with a
larger screen, rather than the standard screen.


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

On Fri, Nov 29, 2019 at 04:30 AM, Dejan Corovic wrote:

So is there a seller on UK eBay or Amazon that you bought before and he wasn't selling fakes?
==============================================================================
I bought mine on eBay, , from seller shuangtai-elec. His positive feedback is very high and delivery time was shorter than estimated by a week. UK and US ebay usually have parallel offerings.

Besides some of its latest enhancements, the reason I purchased the NanoVNA-H is I wanted to support hugen's efforts by purchasing one of his units. Its hard to do that with the original open case design because the cloner's have gotten so good. At this point in time, I have not seen a clone of the NanoVNA-H that is not an obvious fake. Hugen has packaged the NanoVNA-H in a very distinctive box with molded plastic inserts to hold and protect the unit and its various accessories. The enclosed case design for the NanoVNA-H itself is also distinctive. If the unit you purchase is as pictured in the ebay auction that I referenced, then you can be fairly certain it is a hugen product, in this case probably second sourced from him.

- Herb

The known official store of Hugen is here

The other sellers on ebay, aliexpress, amazon, etc are usually selling
clones. Very rarely, some are reselling originals from Hugen.

In my opinion, is better to get the original, which has the latest hardware
upgrades and firmware, and also supporting the developer in this way.

Ady YO2NAA


On Fri, Nov 29, 2019 at 2:30 PM Dejan Corovic via Groups.Io <Dejan.Corovic=
[email protected]> wrote:

Agreed.

So is there a seller on UK eBay or Amazon that you bought before and he
wasn't selling fakes?

Agreed.

So is there a seller on UK eBay or Amazon that you bought before and he wasn't selling fakes?

Owen cannot compare a $10k VNA against a $50 one

I am happy with the cheap and cheerful H version for basic understanding
and experimentation

To expect lab grade performance is ridiculous

John ve3ips
--
Sent with a Palm Pilot. Ve3ips.wordpress.com
Radio: it's not just a hobby, it's a way of life
All content is personal and confidential

I second Don's question. Email?

On Thu, Nov 28, 2019 at 06:14 PM, Dejan Corovic wrote:

This guy is really going deep into NanoVNA-H, finding some problems
================================================================

Yes Owen is a knowledgeable personality but you have to remember that some of the measurements on his site are not something the NanoVNA was marketed for. The fact that he has even found the NanoVNA useable in his applications is testament to its $50 cost versus usability value. Nothing else available in that cost range comes close.

Owen only purchased the NanoVNA-H so his comments are specific to his unit. However the design faults he describes are common to all NanoVNAs and and do not only apply to the NanoVNA-H, for example his following comment:

"I identified a significant defect in my nanovna-H PCB v3.3 (says the label, but yes, it could be a fake, but a very convincing copy) that was traceable to a design failure, inadequate power supply decoupling on the three mixer chips. This was not a fake related issue, the schematic for nanovna-H PCB v3.3 shows inadequate decoupling."

The inadequate decoupling is a fairly well known issue, , but the NanoVNA meets its specifications without the decoupling and adding it will only make it perform better. Hugen, the NanoVNA-H board designer, has indicated he plans to address this and other issues in a future PCB version.

So while Owen's insights about the NanoVNA-H are in general true, they are also generally true about all NanoVNA's.

- Herb

On Thu, Nov 28, 2019 at 06:14 PM, Dejan Corovic wrote:

This guy is really going deep into NanoVNA-H, finding some problems

The author of those articles Owen Duffy is very knowledgeable and I have learned a lot from reading his blog. Sadly he has a penchant for criticizing others and this detracts from his posts. What he says is thoroughly researched and he writes good posts but often at the expense of others.

Hugen seems open to constructive criticism of his design and makes modifications to his circuit to improve it. I applaud him for the way he strives to continually make a better product and look forward to his next design.

This guy is really going deep into NanoVNA-H, finding some problems

Dejan,
Could you reference where you read that the NanoVNA-H is full of hardware issues? The reason I ask is because the NanoVNA-H is hugen's latest release of the original NanoVNA and the only hardware changes he has made are slight improvements like adding a missing diode so that the battery voltage can be read, adding resistors for improved USB-C to USB-C connection, and putting the NanoVNA in a protective case.

I have both the original NanoVNA and the NanoVNA-H and have used them both extensively. The NanoVNA-H is the better value unless you can find the NanoVNA in the twenty dollar range.

- Herb

I want to buy NanoVNA but I am confused with so many vendors and versions of firmare.

I would like to buy on UK eBay so I can return it if it's clone. I read about most recent version NanoVNA-H that it full of hardware issiues.

Is there such a thing as an official NanoVNA hardware or manufacturer.

Who would be the most reliable seller on UK eBay or Amazon?

How to email you? the email address is blanked out after @.

When will the V2 design be manufactured and ready for sale? Any name yet for the product?

On Wed, Nov 13, 2019 at 04:16 PM, Larry Rothman wrote:

There is an interesting discussion on hugen79's NanoVNA Issues page on Github
regarding circuit changes/mods to reduce overall noise levels.

Gentlemen, what you have at Noise improvements.
Outlined in found that the power input at the mixer ICs is
lacking capacity, causing spikes and spur at 6.4 MHz (7.5 MHz at VK1OD) - unfortunately due to careless copying of schematic - or lack of quality control.
Namely, if you look carefully at edy555's designs - given the schematic drawings - there is clearly 100pF in parallel with 100nF on the 8th leg of the mixer ICs.
see edy555 build.gif and edy555 power input.gif drawings there is 100nF parallel 100pF.

73, Gyula HA3HZ