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Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?

 

The last version that hugen released should have that - he creates all his variants at the same time.
Please look at:

On Thursday, February 13, 2020, 12:08:01 p.m. GMT-5, <nanovnagroup@...> wrote:

Care to send us a link to the specific web page of the item?
Thank you.
Re: Serendipitous Stylus

 

Nice! Good discovery :)
Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?

 

On Wed, Feb 12, 2020 at 11:46 AM, Clarence Peckham wrote:
I just bought a nanovna-h with 4" display from amazon with version 4.2 PCB. IT
works very well so far and only took two days to get it.

Clarence, NT7V
Clarence could you please share a link to the web page where you made the purchase?
Thank you.
Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)

 

What was your wire spacing to yield 312 + j286 ohms? There should not be a
large reactive component.

Using 4NEC2, I modeled a 40-meter folded dipole at 50-feet off soil surface
(moderate soil) using 6-inches between the two conductors. The result
showed 352 +/- j0.

I suspect your wire spacing was too great to show such an inductive
impedance.

Dave - W?LEV

On Thu, Feb 13, 2020 at 12:42 PM Chuck Carpenter <w5usj@...> wrote:

Soaring Spitfire,

I doubt that your resistors would measure 200 Ohms at 2 meters? At DC the
resistance will look OK. With any length of leads and some distributed
capacitance the resistors will look like a complex impedance at 148 MHz.
That's what the Nano will be measuring.

Also why do you expect the feed point impedance of the folded dipole to be
300 Ohms? I modeled a 1/2 wave folded dipole (40 inches) at 148 MHz and the
feed point Impedance = 312 + J 286 ohms, slightly long.

If you use the software and selected one of the display options to be R+JX
you will see the plots for R and X over the scanned frequency range.
Together those will be the complex impedance. As noted elsewhere, you need
to include the conversion factors from the coax lengths.

An accurately made coax BalUn for the frequency would be best. Lumped
inductance BalUns at 2 meters get really weird...8^)

Have fun.


--
Chuck, W5USJ



--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?

 

Today I finally got a response from the seller to my follow up message asking if he could post some pictures of the PCB showing the v3.4 label on it, as it would be beneficial to his sales as well.

Seller [you.are.you] said:
"ok,thanks for your suggestion"

Yeah, right, hahaha.
Which firmware for AA contains the "Config" button

 

I just flashed the 800 mhz aa version to my NanoVNA. Works great, but no Config button. Is there a version out there that contains that in the Antenna Analyzer variant?
Re: PL-259 calibration

 

I need a holiday haha. Thanks for confirming my brain is kinda working.... Thanks for the help
Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?

 

A recheck of the EBAY Listing indicates he has 0 units left.. Want to bet he returns with changes in the listing
Re: US based Ebay seller claims he is selling v3.4 NanoVNA - true?

 

The case hides the battery size. I have a pre-3.4 and I upgraded to 1.5Ghz.. THe spec is showing a 400mah battery .. Not 3.4..

I find that 9-5 US time, +/-2 hours he's in the USA in his office.. When you get responses 2-3-4 am he's in China.. If they respond or ship on Sunday's they are in China.
Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)

 

Using NanoVNA SAVER, I calibrate and Sweep using 144Mhz Start 148Mhz end.. and you can set sweep x4.. that's 101 points per MHZ.. It takes a but longer.. The display does look real pretty and if you dump it to printer.. Great..... Now if you are making a filter and using a trimmer cap, each full screen scan takes about 3-4 seconds.. So rotate the trimmer SLOWLY..

There is an advantage to attach an external computer. I don't know the limits, but you can scan more than 101 points. There is a multiplier that divides the span, but increases the points recorded at a decrease in time. A times101 points I've gone to 5.. 5 times as many points 505, and 5 times as long for1 scan. I do not know it's limit.. I'd bet as long as the Start STOP Bandwidth versus synthesizer step isn't exceeded your fine.
Re: Serendipitous Stylus

 

I find that a cotton-tipped swab makes a nice stylus for the nano-VNA touch screen.

Dana K8YUM
Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)

 

I didn't finish the impedance: The RF Z of the R+jX would be about 420 Ohms.

--
Chuck, W5USJ
Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)

 

Soaring Spitfire,

I doubt that your resistors would measure 200 Ohms at 2 meters? At DC the resistance will look OK. With any length of leads and some distributed capacitance the resistors will look like a complex impedance at 148 MHz. That's what the Nano will be measuring.

Also why do you expect the feed point impedance of the folded dipole to be 300 Ohms? I modeled a 1/2 wave folded dipole (40 inches) at 148 MHz and the feed point Impedance = 312 + J 286 ohms, slightly long.

If you use the software and selected one of the display options to be R+JX you will see the plots for R and X over the scanned frequency range. Together those will be the complex impedance. As noted elsewhere, you need to include the conversion factors from the coax lengths.

An accurately made coax BalUn for the frequency would be best. Lumped inductance BalUns at 2 meters get really weird...8^)

Have fun.


--
Chuck, W5USJ
Re: larger screen models same hardware?

 

Hi Kayak,
Since you're new to this, please go through the forum's WIKI and FILES areas.
All your questions have answers there...
The links are at the bottom of every email sent out by the forum but if you're not subscribing, the links are along the left side of the webpage.

On Wednesday, February 12, 2020, 11:26:16 p.m. GMT-5, Kayak <kayak1176@...> wrote:

hi all, new to this. I have a question. are there larger screen
nanovna and with the exact same hardware and reliability etc?? if so,
can someone post a link?

thanks
Re: PL-259 calibration

 

You brain must be really overloaded if you need confirmation about this! So I'll help you, yes, you are right.
But I've seen at least two websites about experiments with optimal resistor topology for a "perfect" load. 1 x 49R9, 2 x 100R, 3 x 150R, 4 x 200R. The best performance was 2 x 100R. Note that the deviations from "perfect" start at frequencies > 1000MHz, so with the PL-259 range of use, you'll be fine.


Op 13-2-2020 om 03:29 schreef Kevin B:

One last one.... My brain has been overloaded lately so just wanted to confirm. If I use 4 parallel resistors for better accuracy as mentioned earlier, 4, 200 ohms will make it 50 ohms correct.
Re: PL-259 calibration

Steen Rudberg
 

Yes Kevin - you are on the right way.

1/ (1/200 + 1/200 +1/200 + 1/200) = 50
larger screen models same hardware?

 

hi all, new to this. I have a question. are there larger screen
nanovna and with the exact same hardware and reliability etc? if so,
can someone post a link?

thanks
Re: PL-259 calibration

 

One last one.... My brain has been overloaded lately so just wanted to confirm. If I use 4 parallel resistors for better accuracy as mentioned earlier, 4, 200 ohms will make it 50 ohms correct.
Re: nanoVNA Maximum Impedance Measurement (Folded Dipole example)

 

Yes. I too have found out that balun is necessary when measuring antennas.
Re: Document available from Element14 -Tools & Test Equipment I: RF Spectrum Analyzer

 

While you are looking at TEK info, take a look at their vna tutor and support info. Excellent.

Alan
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