开云体育

I bought mine from RandL.com ( )
$69
NanoVna Saa2N.
4" 50k to 3Ghz.

Had it four days now
Looking forward to writing my ham c#
App to talk to the serial port

I will make it freeware when finished.

--
Sent from my Android phone with GMX Mail. Please excuse my brevity.

I agree John.

At best my schematic is a circuit rendering.
Maybe the data sheet has info on the required terminations.

On Wednesday 28 October 2020 10:25:10 pm Bob wrote:

Hi all
I bought what I believe is the nanoVNC-h on fleepay. 50kHz - 900MHz 2.8" screen. Was advertised as a 4" touchscreen.
I'm pretty sure it's a clone, a fake and a dud.

The difference in screen size would have had me returning that right off...

It turns on ok but how do I change the range of the scan? I push down on the rocker switch and I get a menu but I can't select a menu item with the rocker switch or the touch screen. I suspect the rocker switch right side is faulty. Only left works and takes away the menu. I can see bursts of sweeped frequency on the Channel 0 output with my little sampling oscilloscope. Didn't even get a basic user guide or even a link to download one.

I bought my first one there too, and the package that it came in was so tight that pressure was exerted on the rocker switch, to the point where it was damaged. You could move it through about a 45 degree angle away from the board, and it just didn't work. I ended up returning that one and getting a refund, and also ordering one with the bigger screen from R&L Electronics, which came in a much nicer package, works well, and I would recomment dealing with those folks. I also ordered SO-239 and BNC adapters with it, reasonably priced.

Currently playing with the vendor who is trying to avoid taking responsibility for his dodgy product. I have now placed an order for a NanoVNC-H4 (4"touch screen) with another fleepay vendor. Will I still be in the right group?

I am real close to giving up completely on that platform. I placed an order back in June for some stuff, got sent the wrong item for one of the three things I ordered, and couldn't get anywhere through their dispute resolution process until I finally got some satisfaction through PayPal...

I joined this group and already learned a lot. The combined knowledge is incredible. Thank you all for sharing. I've been in the electronics industry since 1961 and a Ham since 1977. Still learning new stuff. I'm strictly Hardware. I'll never be a programmer but I have compiled software in Linux following other peoples instructions. Love Linux, hate Microshaft with a passion.

I've run nothing but linux here since 1999. :-)

73 Bob vk2byf

73, WD3WTF.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

Rich, attach a photo so the rest of us know what you're looking at.

Welcome to the group, Bob.
Please refer to any of the user guides mentioned in the Wiki.
You can print the one I edit - it's in the Files section.? Note: every post you receive has links to these areas at the bottom of the email.
If the description said 4" and you got a 2.8" unit from an eBay vendor - open a complaint to get either a refund or the correct unit.
From what you state - it appears you have a bad rocker switch.
Note that these units have touch screens - use that instead of the switch.
Change the freq range using the stimulus menu..
Cheers,
Larry

I'm following this with great interest as this is something that I'm also busy learning about while waiting for my NanoVNA-H4 - thanks for all the valuable info so far!

Hi all
I bought what I believe is the nanoVNC-h on fleepay. 50kHz - 900MHz 2.8" screen. Was advertised as a 4" touchscreen.
I'm pretty sure it's a clone, a fake and a dud.
It turns on ok but how do I change the range of the scan? I push down on the rocker switch and I get a menu but I can't select a menu item with the rocker switch or the touch screen. I suspect the rocker switch right side is faulty. Only left works and takes away the menu. I can see bursts of sweeped frequency on the Channel 0 output with my little sampling oscilloscope. Didn't even get a basic user guide or even a link to download one.

Currently playing with the vendor who is trying to avoid taking responsibility for his dodgy product. I have now placed an order for a NanoVNC-H4 (4"touch screen) with another fleepay vendor. Will I still be in the right group?

I joined this group and already learned a lot. The combined knowledge is incredible. Thank you all for sharing. I've been in the electronics industry since 1961 and a Ham since 1977. Still learning new stuff. I'm strictly Hardware. I'll never be a programmer but I have compiled software in Linux following other peoples instructions. Love Linux, hate Microshaft with a passion.

73 Bob vk2byf
--
No good deed goes unpunished.

I have a new RF Demo Kit board that came with two connecting wires. One end is an SMA male connector and the other end is something that I have never seen before. It is supposed to connect to the test positions on the circuit board. I have not been able to make the connection because it is very resistant and may take a lot more force than I am willing to do before I learn more about it. Any suggestions would be appreciated.

Richard KC9UB

Alan,
I think the actual notch filter is ceramic piezoelectric. Probably more Q in a small package, and easier to keep on frequency.
--John Gord

This arrangement would create the trap --- notch. Assigned a termination of 300 ohms loaded both sides.

The data sheet for the band reject, notch filter or TRAP is located at:



It appears to used in TV receivers and I suspect inside the unit is a series SHUNT C bridged input to output. The external inductor in parallel with the unit forms the band reject or TRAP frequency.

Their are probably 2 more additional shunt C's, one in parallel with the input and the other parallel to the output to signal ground. This all forms a conventional PI topology band reject filter.

Andrea, I will read your various notes and respond as time permits.

Regards, Alan

Andrea,
I am not familiar with the band reject filter in circuit 5, but the filter in circuit 6 is probably a fairly standard 10.7 MHz ceramic bandpass filter once common in FM receivers. These filters are usually designed to work best with a source impedance of 330 ohms and a load impedance of 330 ohms. Circuit 6 provides a load of 50 ohms to the source generator and a source impedance of about 325 ohms to the filter (at the expense of loss in the resistors). The load impedance presented to the filter is just the 50 ohms of the VNA port (since they didn't use R7 and R11). The matching for the filter would have been better with R7 and R11 at 300 ohms and 51 ohms, but I assume that they were not used because the circuit as built is "good enough", and skipping the resistive matching components gives a larger (if less properly filtered) signal at the output.
--John Gord

On Thu, Oct 29, 2020 at 12:40 AM, Andrea IK0RNT wrote:

But
considering this chance I may finally understand what the designer of the
circuits 5 and 6 in the scrap I attach again - I still wonder what L1 is for
in circuit 5, but I can wait to figure out this.

I meant "what the designer [...] wanted to do"

As for the relation between Z and Y, I'm embarassed to confess it still does
not mean any much to me. In other words, I'm terribly embarassed to admit I
still don't what's the importance of using Y instead of Z, since Y is banally
the reciprocal of Z.

I meant "I still don't know".

And now it should be evident I'm oppressed by my own oversights and I'd love having the chance here to edit my messages after I posted them! ;-)

A.

On Thu, Oct 29, 2020 at 12:40 AM, Andrea IK0RNT wrote:

Reading that to achieve the goal of maximum power transfer from a source to a
load just resistors could be used was definitely illuminating. Of course,
power waste in resistors would be an outstanding undesirable aspect. But
considering this chance I may finally understand what the designer of the
circuits 5 and 6 in the scrap I attach again - I still wonder what L1 is for
in circuit 5, but I can wait to figure out this.

I'm sorry, I forgot to attach... :-(

A.

On Mon, Oct 26, 2020 at 02:30 PM, alan victor wrote:

There is a fundamental idea that is easy to grasp but it has big implications
in achieving lossless
impedance matching. Although we can achieve matching between networks with
resistors only,
they waste power. Ideal energy storage elements, like L and C do not and of
course this whole
bit about matching is either about maximizing the power delivered from one
network to another or
providing a source or a load resistance of a particular value to optimize
voltage or current gain for
that network.

So how is this done?! THE BASIC RULE USED IS SIMPLE!

Z=1/Y.

Yep that's it. Given a series circuit, I can transform it to an equivalent
parallel
circuit which has the IDENTICAL voltage, current and frequency response. Wow.
That's
pretty nifty. So if I have a series 50 ohm resistor and I need to terminate a
filter into 150
ohms, I could add a series 100 ohm resistor, wasting power, or I could add a
PIECE of
REACTANCE in series with that 50 ohm resistor and accomplish the same goal.
That is
produce a R value of an EQUIVALENT PARALLEL network OF 150 OHMS from
that single 50 ohm unit.

I tentatively answer this message, though I've read the following ones, both to follow the order of the messages and to possibly get some prompt that I could use to better understand the rest.

Reading that to achieve the goal of maximum power transfer from a source to a load just resistors could be used was definitely illuminating. Of course, power waste in resistors would be an outstanding undesirable aspect. But considering this chance I may finally understand what the designer of the circuits 5 and 6 in the scrap I attach again - I still wonder what L1 is for in circuit 5, but I can wait to figure out this. Would you confirm the designer was interested just in letting the NanoVNA see an about 50 ohm load and in letting the filter components see a source with an about 300 ohm output impedance?
This would address precisely my previous question: why just resistors there? At the same time, I still wonder why the output impedance of the filters is not considered at all. I'm sure a LT10.7MA5 has not a 50 ohm output impedance and I can safely bet a XT6.5MB has not a 50 ohm impedance.

As for the relation between Z and Y, I'm embarassed to confess it still does not mean any much to me. In other words, I'm terribly embarassed to admit I still don't what's the importance of using Y instead of Z, since Y is banally the reciprocal of Z. The only answer I could find so far is pretty miserable: we use Y instead of 1 / Z when we want to want to write something in the form of a product, rather than in the form of a division.

Later on, after reading something you wrote about that relation in one or more of the following messages, I suspected Z could be the output impedance of the source and Y could be the input admittance of the load. But, again, why are we mentioning an input admittance rather than an input impedance? I just didn't feel like asking this, I tried to find an answer elsewhere before, but with no luck.

Thanks!


A.

On 10/28/20 2:17 PM, Zack Widup wrote:

Rogers Corp. provides a calculator called MWI (Microwave Impedance) which I
find extremely useful. You have to sign up for a free account with them
(which I have had anyway). Then you can download MWI 2009.
Also, from my experience, the dielectric constant of FR-4 can be anything
from about 3.9 to 4.8. It varies widely with batches. That is why WA5VJB
bought a large quantity of it, more than he thought he'd use, for his pc
board antenna products. They are all made with the same board batch. People
(a lot of sellers in China) have copied his design but will not get the
same results because they are using boards with a different dielectric
constant.

\

Yes, this is very much the case.
The other strategy is to design your system so you don't care. For instance, the NanoVNA itself is made on what I assume is FR4. But, because there's a calibration process, any variation in the material properties, either batch to batch, or over time, gets compensated in the cal.

I developed a victim detection radar looking for heartbeat and respiration that works at 3GHz, and it's built on commodity FR4, and it doesn't care what the properties are, either - it essentially self calibrates, and is making "relative" measurements over a short time interval (30 seconds), so as long as epsilon doesn't change in that time span, all is good. There's sufficient dynamic range in the system that changes in RF loss don't affect system performance. (or, more properly, there are 10s of dB of RF loss variation in the environment, a few dB here and there in the box itself makes no difference).

For that system we did have to "bound" the performance of the FR-4 - to show that the maximum radiated RF power density was "safe". But that's easy, you just run the circuit model with the dissipation factor set to zero.

Rogers Corp. provides a calculator called MWI (Microwave Impedance) which I
find extremely useful. You have to sign up for a free account with them
(which I have had anyway). Then you can download MWI 2009.

Also, from my experience, the dielectric constant of FR-4 can be anything
from about 3.9 to 4.8. It varies widely with batches. That is why WA5VJB
bought a large quantity of it, more than he thought he'd use, for his pc
board antenna products. They are all made with the same board batch. People
(a lot of sellers in China) have copied his design but will not get the
same results because they are using boards with a different dielectric
constant.

73, Zack W9SZ

On Wed, Oct 28, 2020 at 12:50 PM Jim Lux <jimlux@...> wrote:

On 10/28/20 8:14 AM, Jose Mihotek via groups.io wrote:

Roger & the group,
I stand corrected.The Z0 does change with freq.For coax, the change is

small (<5%).For Ham purposes (HF), it is negligible.For VHF & UHF, if you
use quality coax (Heliax), it is very negligible.For Microstip and Coplanar
Waveguide, FR4 is a very poor choice. it is batch dependent. There is FR4
and there is FR4...You should use Rogers4350B, it is much more stable and
guaranteed.Alumina would be even better...

FR4 or XXXP is significantly cheaper than Rogers, though. There are
plenty of applications where you just don't care. A microwave motion
detector at 10GHz has short traces, and doesn't care what the loss
happens to be.

<>
Virus-free.
www.avast.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Wed, Oct 28, 2020 at 10:22 AM, Erik Kaashoek wrote:

The calibration load

For accurate S11 measurements of that microstrip at 1 GHz. you need a good reference plane and termination load. You can't put an SMA connector at the end of the microstrip and then use a SMA male terminator and get accurate results.

I suggest a quality SMA connector for the input and a small 50 ohm SMD resistor soldered to the end of the microstrip. For calibrating the NanoVNA some female SMA SOL can be made to go on the end of the cable from the VNA. You may need to adjust the offset delay in NanoVNA Saver.



Roger

On 10/28/20 8:14 AM, Jose Mihotek via groups.io wrote:

Roger & the group,
I stand corrected.The Z0 does change with freq.For coax, the change is small (<5%).For Ham purposes (HF), it is negligible.For VHF & UHF, if you use quality coax (Heliax), it is very negligible.For Microstip and Coplanar Waveguide, FR4 is a very poor choice. it is batch dependent. There is FR4 and there is? FR4...You should use Rogers4350B, it is much more stable and guaranteed.Alumina would be even better...

FR4 or XXXP is significantly cheaper than Rogers, though. There are plenty of applications where you just don't care. A microwave motion detector at 10GHz has short traces, and doesn't care what the loss happens to be.

The calibration load

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