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Hugen,
I noticed on the new NanoVNA-H4.2 PCB there is an unpopulated silk-screened area labeled "CARD1". Does that imply that a SanDisk card is in the works for a future version of the NanoVNA-H4? Also, with the increase in the flash size, are there any plans to eventually increase the number of measurement points?

- Herb

On Sat, Jan 11, 2020 at 01:45 PM, Kevin B wrote:

So I just dropped mine and the screen only turns on, nothing is displayed. Does anyone have an actual web link for a replacement?
===========================================

Kevin,
Replacing the screen is a pretty delicate de-soldering and re-soldering operation. Totally doable if you have good soldering skills. If not, you might consider putting the money for a new screens towards purchasing the new 4" screen version of the NanoVNA-H4. The LCD for the NanoVNA-H4 is not soldered to the pcb (see attachment) so if you have an "Oops, I did it again" moment, screen replacement should be easier.

Sorry about your screen and not answering your original link request.

- Herb

Hi Dave,

Yes, you are right: There are good examples when we don't want or need perfect conjugate match by
design (or whatever other) reasons.

No matter, if we need it, can use it, or want it or not, (b) still generally describes physics of power
transfer, while (a) doesn't - except for the quite common special case: No generator reactance.
In this special case the general formula (a) flaw (wrong reactance compensation) is zero, as Z1 = Z1*.
In an almost tuned situation, the fault is marginal only and in practice often hardly matters. So the (a)
or (b) question often is no big issue. For electrically short antennas it may, however, be significant.

We are talking about a connection of two impedances, be they made of lumped serial elements, or be
they the Thévenin impedance at some point (=equivalent impedance toward the generator), connected
to the load impedance (=equivalent impedance toward the load).

And we are talking about physically correct power transfer description, which mostly is what we want,
unless the aim is echo suppression, maybe for an old time analog TV ghost suppression, stealth radar
applications, or whistle suppression on long phone lines. In these cases the reflection suppressionn is
most important, and there we correctly must use (a) instead of (b).

Reflection at a line termination, correctly described by (a), is not the same physical phenomenon as the
role of impedances in a serial circuit, that only is generally correctly described by (b). (Any parallel circuit
could be recalculated to be a serial equivalent, so "serial" will do.)

Contrary to echo suppression, however, most DXers want to get through in a pileup. Maximum possible
signal received by the rare DX station is achieved by max. real power transferred to our transmitting antenna.
I never heard of echo suppression in that context.


Thanks, Dave for suggesting your nice application of a modern very low internal resistance PA.

These units have a limit: That usually is max. PA heat dissipation. That's why the specs allow a certain max. SWR,
or else the TX protection circuit will reduce RF power or even switch off. In most 1.8 ... 30 MHz low internal resistance
PAs we have filters for different frequency ranges. These are necessary to suppress possible oscillations at certain
frequencies. Because of these filters we don't have a purely resistive internal impedance at the antenna socket.


A look at the PA specs:

Let's arbitrarily assume your modern PA has an internal generator impedance of 8 +j 2 Ohms at a frequency of interest.
Let's further assume, the PA's max. permitted SWR is 2.0 with 50 + j 0 Ohms reference.

This indeed means, we cannot make full use of perfect conjugate match anyway, be it using (a) or (b). For some,
the discussion here ends. That's ok. But let's have a closer look:

If we had no reactive parts in the generator, max power could be sent to the antenna, if the load was 25 + j 0 Ohms:
But we have a reactive part of + j2 Ohms, that (b) will compensate, while (a) would not compensate, but double it.

Resulting from (a) is a blind current that does not increase the radiated real power, only unnecessarily increases the current
through the generator's 8 Ohm resistive part, causing more heat in it and sooner action of the protection circuit, triggered
by the somewhat worse SWR due to the (doubled) reactive component.

On the bottom line:

I cannot see why your modern PA application could causes (a) to be any better than (b) - as both are limited by other reasons.
(a) is even limited a bit earlier.

Nothing speaks against (b) when trying to generally make best power match in so many applications.

Having said this: SimSmith (though not in the manual, but elsewhere: W0QE, who made many videos on SimSmith) sais:

You should us Z1* instead of Z1.
That is only correct for perfect match. Otherwise it would
result in:

Gamma = (Z1 - Z1*) / (Z2 + Z1*) (c).
But sorry: That also does not generally compensate the reactive parts either, except at perfect conjugate match. Only (b) does.

So (c) also does not correctly describe power transfer for poorly matched situations, that in practice easily do occur, as antenna
heights and resonance as well as ground conditions often cannot be changed to what would be the perfect ideal 50 + j0 Ohm
feedpoint impedance.


But - in spite of all above: I cannot stress it often enough:

I have not seen any better free software for the earnest radio amateur than SimSmith.
The missing of (b) can never be a good enough reason to not use SimSmith.

Go, get it, if you havn't yet.

If you know (b), you can calculate with it in SimSmith. Just use the plots feature. It accepts complex math formula.

So the value of mentioning (b), though the theory is correct, imho is worth not much more than a necessary footnote.
Many only know (a) and it serves them, too. Though scarcely known, others use (b), but SimSmith doesn't.

73, Hans
DJ7BA

-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von David Eckhardt
Gesendet: Samstag, 11. Januar 2020 17:13
An: NANO VNA <[email protected]>
Betreff: Re: [nanovna-users] SimSmith - great, not only for Measuring resonance from coax far end.

Dig further back into the matching system. In our modern transceivers, the match begins at the collector / drain of the output devices (the PA).
There is typically no attempt to do conjugation at that point, just bring the impedance from the (generally) far left of the Smith Chart to something significantly closer to the center of the chart. This must be accomplished in a broadband manner.

Dave - W?LEV

--

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

So I just dropped mine and the screen only turns on, nothing is displayed. Does anyone have an actual web link for a replacement?

On Wed, Jan 8, 2020 at 09:46 AM, Larry Rothman wrote:

if you ever perform a full clearconfig command via the console or install new
firmware, you will need to reset the threshold level again.

Gee, it would sure be nice if some of the firmware upgrade instructions actually mentioned that you need to reset
the threshold level. :-)

Hi can some one compare the 4" Nanovna V Nanovna-F, Good and bad points, not just the cost,
Thanks Dave 2E0DMB

Those who ordered anything from China recently, be aware that it's soon the Ney Year's Holiday (rat year) so orders myy be delayed.

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

I ordered the 4” yesterday from Hugen’s Alibaba presence and Maggie emailed me a PayPal invoice at 8:01 Saturday morning her time. Her reply to my payment did not come back to my personal email address, but stayed inside the Alibaba messaging system.

I’m looking forward to the larger screen and other improvements :-).

It would be 4:00 am Sunday for her right now.

73
Bruce W4CG

Yes, Express.? No acknowledgement of the order yet...maybe they do not work weekends ;-)

73

Glen K4KV

Looking forward to your review. Did you order with express shipping?

Roger

Perhaps, the displY can wait till the actual measurements were made and
logged for display.
This might help a noise reduction due to display drive signals.

Ok, great. If you are trying to look at the pass band insertion loss response while at the same time the rejection response, dynamic range may very well get in your way. If that sort of measurement is required than one method is separate out each measurement challenge. Go for IL first and then try to eek out as low a noise floor as possible while driving the filter with as much signal as the analyzer will tolerate. Unlike other vna's this has no BW adjust or video filter tweak. Although averaging helps quite a bit.

Jim,

I use Linux Mint 19.2 Cinnamon on my Chromebook and I believe I had trouble running nanovna-saver because qtxcb was missing. Try installing it with "sudo apt install qt5dxcb-plugin" and see if that helps. Mint 19.3 won't run on my Chromebook (no video) but otherwise there shouldn't be too much difference between Mint 19.2 and 19.3 to cause trouble with nanovna-saver.

Jerry AC9NM

an other suggestion:

Dig further back into the matching system. In our modern transceivers, the
match begins at the collector / drain of the output devices (the PA).
There is typically no attempt to do conjugation at that point, just bring
the impedance from the (generally) far left of the Smith Chart to something
significantly closer to the center of the chart. This must be accomplished
in a broadband manner.

Dave - W?LEV

--

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

After you get it installed, you can make a shortcut by right clicking on the desktop and select "Create Launcher here"
I just called mine NanoVNA Saver and browsed for an unused system icon. The command for my system was
python3.7 /home/andrew/nanovna-saver/nanovna-saver.py

Procedure may be slightly different with Mate. Also of course your path will be different as well.

As a side note, you can also install AntScope 2, the RigExpert software. It won't connect to the NanoVNA but you can open the saved files to play around with.
You'll want the Ubuntu 18.04 version for Mint 19.3

--
Andrew Harmon - KD5RKO

If so, then this is a bad solution to the problem. A photo.

I'm using 19.3 Cinnamon myself. If I remember correctly, I had to install a few dependencies first.
Try this first
sudo apt install python3.7 python3-pip python3-distutils python3-setuptools python3-wheel
then

git clone
cd nanovna-saver
python3.7 -m pip install .

Don't forget the space then . after install
then
python3.7 nanovna-saver.py
Should open after that. Let me know where you get errors.
Also I made a shortcut on my desktop to launch it.

Good morning Alan,
I did as you suggested,
I know where the issue is now.
I neglected to take into account the dynamic range of the instrument.
The filter is a 40 meter filter down -78 dB so I was in the noise floor.
I did a cal and tested the nano with precision attenuators from mini circuits.
-10, -20, -40, and putting them together -70.
Down to - 70 dB it reads within .25 dB.
It still would be good to know if the amplitude could be adjusted in the software.

Classic case of pilot error!

Thanks for your help
Ed

Filter response is very dependent on terminations. Higher load Z than filter designed load will increase coupling between filter elements, widening bandwidth and usually increases loss. Lower load Z will decrease coupling between elements and narrows filter bandwidth. Loss and ripple may decrease if the filter design was in Chebyshev region or loss could get greater if original design was Butterworth or Gaussian. The S21 input port Z is not very good so attenuator pad will help reduce the load variation. Spectrum analyzer has similar issue on its input. Any reactance in the load will detune the filter elements.

You did not mention the filter design frequency.

I have a nanoVNA, nanoVNA-F, and N1201SA units. The N1201SA is much better performance then nano's for S11 measurement. N1201SA at 1 GHz has about 50 dB dynamic range where the nano's are lucky to get 30 dB. Number on Z readout on N1201SA is much more stable and doesn't jump around like nano's.

The main difference in the N1201SA with its ADF4351 synthesizer is providing fundamental Tx signal where the nano's using the Si5351B must rely on harmonics for Tx above 300 MHz. Both use harmonic LO downmixer with the SA612 mixer.

I looked up specs for the synthesizer chips and the jitter for the Si5351B is very poor. The ADF4351(or ADF4350) is very good. The Si5351 is between 70 and 100 ps of jitter where the ADF4351 is less then 0.5 ps. That is a dramatic difference. The Tx jitter and Rx jitter are mostly independent since they are different dividers so their jitter stacks up to make things worse.

This impacts the dynamic range. The jitter at harmonics on the nano's is likely so bad that it is 'fuzzing up' the 5 KHz downconversion output to the point that it impacts the ability to measure the signal accurately.

There may be other factors such as if and how any smoothing averaging may being done or even layout/power supply noise differences. I am going to look at the Tx signals on spectrum analyzer on both units.