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

--
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."
===========================================================================================================
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!! :-))

--
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.

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
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!.

Glen K4KV said: "One comment I will make, and not to upset anyone, but
there seemed to be a fixation on cost. Take my viewpoint: I spent $600
building my N2PK VNA, so getting a really great nano at, say, at $125 is no
big deal. Bigger screen, Ghz oscillator, beefier connectors is all good!"

I couldn't agree more. I would add to that list quality coax, connectors,
and calibration standards. At least as upgrade options. The first thing I
will do when I buy a NanoVNA is to upgrade all of these items anyway.
Thanks!


--
Ed Jones - K8MEJ - Lewis Center, Ohio U.S.A

Erik, thanks for responding.

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.

On Fri, Dec 27, 2019 at 07:52 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.

Was searching for info on the v3.4 improvements and found this from hugen79 at a Gidhub message exchange where he mentions at least one of the improvements:

hugen79 commented Nov 12, 2019: Noise problems introduced by USB connection I will use the new power chip in NanoVNA-H V3.4 to improve this problem. I will try to increase the capacitance of the si5351 to reduce noise. The problem of LED flicker noise can be improved by software.

Whole thread is here:


I assume most of those improvements might mostly have to do with reduced noise on the extended or upper frequency ranges? Since I would mostly be using it for 500MHz at most and much lower frequencies, perhaps I could get by for now with an older v3.3 board. Still be nice to have the latest revision.

In any case opened an Alibb account to be able to send M.King a message to ask if they might know of any ebay seller that has the most up to date v3.4 board in stock. Lets see what they answer. Thanks.

How do you normally operate the ladder line?
Using a balun or via an antenna tuner that provides balanced output?
In case you use a balun simply connect the nanoVNA to the balun and measure.
When using an antenna tuner disable all "tuning" and use the tuner as a pure balun.

Without a balun (in case your receiver has something buildin) your proposed approach will work but be aware the ladder line impedance is high compare to 50ohm

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

On 2019-12-28 9:59, Dana Whitlow wrote:

Some things to consider about online purchases:

.....................................

The technique I use is a bit different. The credit card offered by my bank has a special function, that allows to generate a one-use-only credit card number, meaning that after that number has been used once, is no more valid... additionally, you can specify the maximum amount that CC number can be charged from.

So, when buying online from a vendor that does not accept Paypal, I generate such a CC number, specifying a max amount just slightly larger than the cost of the item, and send it.
This way I am sure the vendor cannot reuse that CC number or charge me a large amount of money....

--
/*73 Alberto I2PHD*
<<< >>>/

How would you do it?

I'm thinking that first, I'd need to construct an adapter for the VNA - sma connector, short length of coax, with clips on the center conductor and shield to clip to the two sides of the ladder line (but, the quality of the connection between the clips and the ladder line wires (among other things) is going to introduce variables, right?)

Second, I should calibrate for the desired frequency range using the adapter as described above, in order to "calibrate out" as much of the peculiarities of the measurement system as I can - I would clip my adapter to my QRP-Labs dummy load for the load part, leave the clips dangling for the open, and clip them together for the through.

What kind of trouble am I going to be getting myself into?

Herb,

Thanks for the information.? Obviously, I am new here, and do not own a unit yet.? I have a N2PK VNA, that has

now started to act up.? It is pretty much a laboratory piece of equipment, comparing very favorably with the HP unit.

But now it is sick, and was limited to 60Mhz.

So, now am going to buy the nano, but want a bigger screen.? My N2PK VNA is just a black box with which you MUST have

a PC.? Having a link to pc software is essential when doing circuit development.? One has to compare the old scan with the

latest one.

One comment I will make, and not to upset anyone, but there seemed to be a fixation on cost.? Take my viewpoint: I spent

$600 building my N2PK VNA, so getting a really great nano at, say, at $125 is no big deal.? Bigger screen, Ghz oscillator, beefier

connectors is all good!

73

Glen K4KV

On Sat, Dec 28, 2019 at 03:55 AM, GmailK4KV wrote:

I do this kind of stuff too, and get NO help ;-) being a "one-man" show. I have to do the hardware AND software.
=======================================================================================
Glen,
hugen pretty much has been where you are except he was able to piggyback his efforts on edy555's prior design. His original NanoVNA-sharp software was barebones, but demonstrated the solid communications api of edy555's original firmware. Additional support that hugen has received from the community has been because of the true open source nature of The NanoVNA design. Everything from source code to schematics is readily available on GitHub. I admire that hugen hasn't rested on his laurels but continues to innovate and contribute to the general NanoVNA community.

- Herb

On Fri, Dec 27, 2019 at 11:44 PM, <hugen@...> wrote:

"...I will print the NanoVNA-H label and the hardware version number on the PCB I sell, and there will be a QR code next to the screen of the main pcb for accessing nanovna.com."
=================================================================
hugen,
May I also suggest that the label that you now attach to the back of the NanoVNA-H case include the PCB version number. That information is currently not accessible without taking apart the case. Congrats to all who contributed to the development of the NanoVNA-H 4. Especially proud that some members of this group contributed.

- Herb