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erik, interesting video, which I will review at length another time. For the moment, I am trying to get a handle on an actual, physical system, to give myself a framework for understanding. The information (in various forms) available on the internet is, for me, essentially infinite - I mean that there is far more than I will be able to read/watch/comprehend in the time I have remaining on this earth. I have always had an easier time comprehending when I have a physical model that I can manipulate, therefore my efforts, here, to learn how to characterize the model I have available to me, that is, my antenna system.

This is my answer, also, to the post from vaclav_sal (for which, thank you). The information in your post is valuable, I'm sure, and, when I have attained a reasonable comprehension of my particular antenna system, I hope I will be able to use it. And, by the way, a "multi-band" antenna is my eventual goal - which I hope to reach before I am too old and decrepit to use it.

Hugen,

Looking forward to this version. When do you think it will be available?

I'm trying to keep track of each version.

Mike N2MS

On Sat, Dec 28, 2019 at 07:48 AM, Birdman wrote:

So how long off before this new unit is available for purchase? Weeks, Months, a year, years?

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Given hugen's history on this forum, he generally doesn't start making announcements until he feels his final prototype is ready for production. Of course after prototyping is complete he stills has to line up suppliers for parts, have pcb's mass produced, and prototype case designs. Hugen has also indicated that if his final design is marketed as having a high end frequency of 1500 MHz, he will probably seek different cable (RG-316?) suppliers.

Knowing the above you can probably make an educated guess about availability for purchase. With hugen's experience in bringing the NanoVNA and NanoVNA-H to the marketplace he probably already has developed a pretty good network of suppliers so he won't be starting from scratch in that aspect. How many of the 4" LCD's he can line up may be another factor. The Chinese new year is January 25th and also has to be taken into account.

In any event, the 2.8" NanoVNA-H with version 3.4 pcb is already being sold at his Alibaba store and offers most of the coming features except for the 4" LCD and F303.

- Herb

If you are interested in doing a detailed analysis you may be interested in how simsmith can help you
Here is an excellent video explaining how to do impedance matching analysis including where the power goes.


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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

For the moment, I'm just trying to understand what is going on, impedance-wise, with my antenna system. Not that I am having "problems" that need to be "solved," just curious.

When operating, I will have the following: 130+ feet of copperweld, hung about 60 feet up between two trees, center fed with about 100 feet of 450 ohm ladder line, connected to a 1:1 current balun, short coax run to a ground buss, short coax run from buss to tuner, coax from tuner to radio. I would like to understand what sort of impedance transformation is happening at each connection/through each element.

First of all _since I DID NOT READ ALL MESSAGES in the discussion, this may be a dupe.
If so - my apology.

Analyzing the above post - here is my reply / attempt to put the whole "impedance issues " in different perspective.
AND ONLY the impedance / balance issues !
130 cubits, sorry I measure in meters, center fed radiator ( antenna) is missing few "dimensions" .

So I will make an assumptions.
Its BASIC intent to RESONATE on FUNDAMENTAL frequency
hence
it is half wavelength long on such fundamental frequency , commonly referred to as (center fed ) dipole antenna.

As such it has FEED POINT IMPEDANCE of roughly 70 Ohms AND it is a BALANCED radiator when fed in center.
Ideally it should be fed using BALANCED feed line of CHARACTERISTIC impedance close to 70 Ohms.
( common "zip line" is OK to use )
In practice it is generally fed with UNBALANCED coaxial feed line of CHARACTERISTIC impedance ranging from 50 to 75 Ohms.

The differences / mismatch in feed point impedance and feed line characteristic impedance are not worth writing home about.

However, the connection of unbalanced feed line to balanced antenna is worth futzing about - hence BALANCED TO UNBALANCED (matching BALUN ) transformer is commonly utilized.
Please note that the (BALUM) transformation ratio IS 1:1 - again ignoring slight differences in impedance.

There are other BENEFITS besides matching the impedance , but my point was to concentrate on impadnces of the SYSTEM from antenna perspective on SINGLE fundamental frequency.

It is a horse of different color when "multiband antenna" is the goal.

Practical measurement using a 1:1 balun, connected the nanoVNA to one side, other side to the ladder line of a half size G5RV. The ladder line does the impedance transformation to the dipole of the G5RV
I'm displaying the SWR instead of the impedance but you can display what you want.

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NanoVNA Wiki: /g/nanovna-users/wiki/home
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Erik, PD0EK

When using a 1:9 transformer you should connect the nanoVNA to the "1" side and the ladder line to the "9" side.
For calibration use a 450 ohm resistor (or a 470 ohm with a second resistor to make it 450 ohm) connected to the "9" side, and a short (short wire between the two terminals) and a open.
Due to the transformer the nanoVNA will see the 450ohm as 50ohm and will easily calibrate
Don't bother about the 450 ohm resistor not being perfect. Your antenna is probably worse
And yes, the 1:9 transformer/balun will only be realy 1:9 when loaded with 450 ohm but you will still see the difference when other impedances are connected to the "9" side.

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NanoVNA Wiki: /g/nanovna-users/wiki/home
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Erik, PD0EK

W5DXP, thanks again, good information.

With regard to your previous post, and calibration at the "measurement plane." II understand correctly, this means conducting the SOLT calibration procedure with a 50 ohm resistive load at the point of interest in the network. In the instance of wishing to measure the impedance at the end of the ladder line on the far side of the 1:1 balun, I would connect the VNA to the balun, and conduct the SOLT calibration at the balun output - in my case, a pair of terminal posts. So, with the VNA connected to the input side of the balun, I would first short the output terminal posts, then leave them open, then install a 50 ohm resistive load between them, and...I wouldn't do the "through" calibration, in this case. After the calibration steps, I would connect my ladder line to the balun's output terminal posts, and would then be looking at the impedance of the feed-line/dipole network at the point where it connects to the balun. Correct? And, if so, what would be the most appropriate way to connect the 50 ohm load across the output terminal posts for the "L" portion of the calibration?

Silly me!! I was not paying attention to “PCB”... I was fixated on “version”... Thanks for the info!

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Regards,
Chris

So how long off before this new unit is available for purchase? Weeks, Months, a year, years?

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Regards,
Chris

From: entilleser@... So, presuming that I have a 450 ohm load at the end of the ladder line (which might not necessarily be true, under the circumstances), by connecting the VNA to the 1:9 balun, the VNA should report an impedance of 50 ohms, correct? ... For example, if the actual impedance at the end of the ladder line were 900 ohms, the VNA would report an impedance of 100 ohms.

Concerning ideal TLTs: First sentence above is true. Second sentence is false. A Transmission Line Transformer has an electrical length. If the load on the 9:1 TLT-balun is not the designed-for load of 450 ohms, the transformation will not be 9:1. A TLT is NOT an ordinary (N1/N2)^2 transformer. Another way of saying the same thing is: If the SWR on the 450 ohm ladder line connected to a 9:1 TLT is not 1:1, then the impedance transformation ratio will most probably not be 9:1. As an illustration, here is a graph of the impedance at the output of a 50 ohm 1:1 TLT vs the "transformed" impedance at the input of the 1:1 TLT. Note that the only point at which the transformation ration is close to 1:1 is when the impedance at the output is close to 50 ohms.

On Sat, Dec 28, 2019 at 07:10 AM, Birdman wrote:

"Is it not possible to update the bios/software on these units? I assumed they can be and didn’t even consider the version on it."
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Chris,
The ver 3.4 that was discussed is the new hardware version of the printed circuit board. You are correct about the firmware/software being easily upgradable to different versions, which has contributed to the popularity of the NanoVNA units. However, if you want the latest and greatest hardware changes then you have to purchase a NanoVNA-H with a ver 3.4 printed circuit board. hugen posted some screenshots last night in another message thread that show improved ver 3.4 PCB performance out to 1500 MHz.


- Herb

W5DXP, thanks for your response...I think... What I mean is that you have provided me with another thing to learn about, that is how to "calibrate your measurement plane at ..." Do you have any reference I could use to learn about this?

Also, in reference to my immediately previous post, I believe I should have said "...a purely resistive 450 ohm load..."

On Sat, Dec 28, 2019 at 06:31 AM, DJ7BA wrote:

" ,,, the Lambda/8 method is not commonly known... "
=================================================

The method is more useful when you have an instrument like the NanoVNA where you can visually determine the first zero ohm Lambda/8 resonance point and then quickly set the Lambda/4 CW frequency and read the impedance.

The method would be even more useful if the algorithm could be automated to program the NanoVNA to perform all the above and display the cable impedance.

- Herb

On Fri, Dec 27, 2019 at 10:52 AM, hwalker wrote:

About the only other consideration I can think of is hugen has made some
worthwhile improvements which he has included in Version 3.4 of his PCB. If
you order from his official store your NanoVNA-H will have the ver 3.4 PCB
installed. If you order from eBay or elsewhere there is no guarantee which
version PCB will be installed.

- Herb

Hi Herb,
I’m also new to this, and ordered a NanoVNA which is arriving today. Is it not possible to update the bios/software on these units? I assumed they can be and didn’t even consider the version on it.

Thanks for the info.... I’m excited to play around with this device and test/compare a few antennas I use, and pretend I know what I’m doing!! :-))

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Regards,
Chris

From: entilleser@... Measuring impedance at the bottom end of a ladder-line-center-fed wire dipole - How would you do it?

I've done it. Simply calibrate your measurement plane at the output of the balun that feeds the ladder line. The attached graph was done with an AIM-4170D but the calibration procedure for it and the NanoVNA are the same. The top graph was done with the calibration plane at the output of the balun and the bottom trace was done with the calibration plane at the input to the balun.

Erik, if I understand correctly, the purpose of the 1:9 balun is to reduce impedance by a factor of 9. So, presuming that I have a 450 ohm load at the end of the ladder line (which might not necessarily be true, under the circumstances), by connecting the VNA to the 1:9 balun, the VNA should report an impedance of 50 ohms, correct? Any deviation from 450 ohms at the end of the ladder line would show up as a deviation from 50 ohms on the VNA, at 1/9th the deviation at the end of the ladder line, correct? For example, if the actual impedance at the end of the ladder line were 900 ohms, the VNA would report an impedance of 100 ohms.

Yes, the ladder line is (nominally) 450 ohms, and the coax (nominally) 50 ohms. I am working to understand the use of a balanced matching network, the intended purpose of which is to transform the impedance of the ladder line to an impedance appropriate for the coax, but that is for another day.

I will have to study up on "TDR" mode - I get the general idea (impedance as a function of the distance from the measuring device to a specific location in the network), but I am not at all certain I understand it well enough to derive any significant information from its use in the present circumstances.

For the time being, I prefer to measure impedance at the location of each connection. I'd measure at the end of the ladder line, then at the coax side of the 1:1 balun, then at the end of the coax that would be connected to the ground buss, then at the other side of the buss, then at the end of the coax that would be connected to my tuner, then at the other side of the tuner, and finally, at the end of the coax that will connect the tuner to my radio... Whew!

Hi

Helmut, Nick, Corneliu and Martin,

thanks for the kind replies - indicating that the Lambda/8 method is not commonly known.
The value measured that way is good for just that one Lambda/8 frequency.
The Method is fast and easy. It saves time and quite often is all you need.
That is the strength of this method, that I first learned from DC1MKR in our local club.

If maximum precision is your need, not just fast practical results, you will prefer the frequency
dependent cable properties described by AC6LA. Find it, for example, in:

Zplots.xls and applied in
SimSmith

for many popular cable types and makes.

Both freeware programs are highly recommended to all NanoVNA users.

73, Hans
DJ7BA











-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von Roger Need via Groups.Io
Gesendet: Freitag, 27. Dezember 2019 19:19
An: [email protected]
Betreff: Re: [nanovna-users] quick measuring cable characteristic wave resistance

I experimented with this Lambda/8 method using the program TLD (transmission Line Details) and got within .4 ohms of the cable impedance after doing a number of different tests. TLD contains the characteristics of many kinds of cables and calculates input impedance at various frequencies/line lengths based on a user input load impedance.

TLD is a free program and is available here >>> . Highly recommended

Consider buying one of these

and use it between the nanoVNA and the ladder line (without your 1:1 balun). This will allow you to measure with best accuracy even if you have calibrated the nanoVNA with the standard calibration set.
Your 1:1 balun may not be optimal as the ladder line is 450 ohm and coax something like 50ohm (?)

To understand each impedance transformation connect the nanoVNA instead of the radio and switch to TDR mode.

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Erik, PD0EK

For me the biggest issue with these has been the small display!,in the uk the f model is over ?100 as oposed to the h model at about ?30 ish,ive ordered a 3.2 inch screen for mine,not ideal but better than standard from the price point of view!.