开云体育

Chris,

there is no need for a Kindle E-reader, as it is possible to read Kindle books on many devices like tablets, smartphones and computers. Check for free apps and online readers.

Concerning media, I'm sorry but we do not intend to publish in any other form currently.

Vy 73,
Chris, OE1CGS
====================================

Congratulations on the book, both, what a great gift for the Ney Year! Just been watching the concert from Vienna.

- I would have liked to see more on the NanoVNA-F, as it's a little different from the basic model.

- As recent models (basic and -F) include an easier way of updating the firmware, perhaps give that prominence over the earlier method (but keep that for reference).

- i hope that Amazon will be able to offer updates at no charge. I've seen that on other books. I can see the updates coming quite frequently!

Thanks, and a Gutes Neues Jahr.

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Thanks for the information, just purchased. 73 Ade M0OJR.

Chris,

there is no need for a Kindle E-reader, as it is possible to read Kindle books on many devices like tablets, smartphones and computers. Check for free apps and online readers.

Concerning media, I'm sorry but we do not intend to publish in any other form currently.

Vy 73,
Chris, OE1CGS

Hi, i'm a newby to this but have the same problem. i'm running Win7 and under device manager is shows 'STM32 Bootloader' If I delete this and plug in my Nanovna in DFU mode, the same driver gets reloaded. I can't get dFuSedemo to recognise it.
Any ideas what I am doing wrong please.

Ken G4APB

Jeff,

Your knife pointer (clever idea, BTW) is pointing to a terminal of something
which appears to be C11, if I'm reading the fuzzy photo correctly. This is not
shown on the schematic, leading to confusion.

Also, the schematic does not reflect the mutual inductance between L1 & L2,
which is probably pretty significant judging by their end-to-end proximity as
shown in the photo.

If you really want to measure the filter, you're going to need to disconnect
the input of the shielded thingy, and add a coax connection to the CH1 port
of your nano-VNA from that end of the filter. Or, for a partial measurement,
just use a 50-ohm resistor terminating that end of the filter to GND and be
satisfied with measuring S11 as seen by the nano's CH0 port.

I would tend to avoid making any measurement with the nano while the
shielded block is connected. For such a measurement to mean anything
the unit would have to be powered up, and the high level signal sent out
by the nano's CH0 port is at risk of overdriving the shielded block hard
enough to affect its input impedance (and maybe even cause damage,
heaven forbid). You could mitigate the overload risks by inserting a pad
between CH0 and the antenna port of the board and calibrating the nano
at the end of that pad, so that the pad's attenuation etc get absorbed into
the calibration. The question is: is the nano good enough to permit making
a meaningful calibration through a pad of sufficient attenuation (I'd suggest
a minimum of 10 dB, with 20 dB or more being preferred)?

This measurement kind of opens a can of worms. If it's just for the sake of
satisfying a curiosity, I'd suggest the old adage "if it ain't broke, don't fix it".
There are plenty of other ways to learn about VNAs without getting into
confusing (and potentially damaging) situations like this one.

Dana

Rudi,

I'd suggest making a measurement at one end of your mystery cable
with the far end terminated in 50 ohms, up to a bit beyond the half-wave
frequency. If the cable is truly 50 ohms, you should see a quite
constant 50 ohms at the VNA end. Labeling notwithstanding, you may
actually be looking at a piece of 75-ohm cable.

I once had a length of a cable which was about RG-8 in size, having
foam dielectric, claiming to be 50 ohms; it was actually about 63 ohms
based on a TDR measurement. I kept it around and eventually used
two quarter-wave sections, one at each end of a run of 75-ohm CATV
hard line, in a 2m repeater setup. It worked beautifully and saved us
the considerable expense of buying an equivalent-length run of 50-ohm
hard line.

Dana

Rudi,

I'd suggest making a measurement at one end of your mystery cable
with the far end terminated in 50 ohms, up to a bit beyond the half-wave
frequency. If the cable is truly 50 ohms, you should see a quite
constant 50 ohms at the VNA end. Labeling notwithstanding, you may
actually be looking at a piece of 75-ohm cable.

I once had a length of a cable which was about RG-8 in size, having
foam dielectric, claiming to be 50 ohms; it was actually about 63 ohms
based on a TDR measurement. I kept it around and eventually used
two quarter-wave sections, one at each end of a run of 75-ohm CATV
hard line, in a 2m repeater setup. It worked beautifully and saved us
the considerable expense of buying an equivalent-length run of 50-ohm
hard line.

Dana

On Tue, 31 Dec 2019 16:44:02 -0800, you wrote:

Von: DJ7BA

Use magnifying glass to make sure if it really was RG58 - or was it perhaps RG59 ?

Hello Hans,
please see the attached photo of the coax cable: RG58_50-Ohm_IMG_1775.JPG

Then I measured a 100 cm RG316 50 Ohm coax cable.
This shows 51.2 Ohm, see attached: Coax_Lambda-div-8_RG316-100cm_51R2.png

Hence, the mystery is going on.

73, Rudi DL5FA

Why not do a cross-check with a different mehod.

Open cable, measure capacitance,
shorted cable, measure inductance,
then calculate Z from the well known formula :-).

And yes, many "50" ohm cables are actually 51 Ohm.
Some are 52 Ohm.


OE8UWW

HNY, Rudy,

at a closer look to your Coax-Lambda-div-8_RG58-100cm.png I could only find a small error,
that I think is not the cause, but it might cause you to repeat the measurement:

f1 = 54.8386 MHz
f1/2 = 27.4193 MHz

but you used
f2 = 27.4442 MHz

Further, I found that this RG58 seems to have very bad attenuation: At f1 it has already 4 Ohm real part.
that is somewhat suspicious. It could be a very bad piece of cable or maybe also a poor connection. I don't know.
Some so-called RG58 cables available today are bad quality. I once returned a brand new 100m roll to the seller
because of that. It is not very unthinkable that the printed on "RG58" is wrong. Have a look at the cable. If the
inner conductor seems to be too small for a 50 Ohm cable, that could be the reason, too.

Please understand, that the formula, the Lambda/8 Method is based on, uses an "ideal" (lossless) cable.
That is in practice often is nearly true, but in this case we certainly cannot confirm that.

Lossy cable in theory has a characteristic impedance that is not purely real only. If that was part of the reason here,
I don't know.

What can we do?

We can repeat the measurement with a different brand RG58 and compare.

73, Hans
DJ7BA

-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von reuterr@...
Gesendet: Dienstag, 31. Dezember 2019 19:19
An: [email protected]
Betreff: Re: [nanovna-users] quick measuring cable characteristic wave resistance

*Problem with RG58 coax cable.*

I tried a 100 cm RG58, 50 Ohm (printed on cable) coax cable with the Lambda/8 measurement.
At the Marker 1 minimum reactance of -j0.054 Ohm and 54.8386 MHz, I got at the Marker 2 half frequency 27.428 MHz a reactance of 76.9 Ohm.
How can that be? What I am doing wrong?
Please see the attached screen shot: Coax_Lambda-div-8_RG58-100cm_76R9.png

73, Rudi DL5FA

Will it become avail on any other media?

--
Regards,
Chris

You need to break the connection to the output of the DRA818V.. it has a pi network inside it's case. That will effect your measurements. The purpose of the "network" in the schematic is to reduce the harmonics from the module to meet FCC specifications. To analyze a pi network, you would connect the network across both connections on the NanoVNA. You can google more info..

Happy New Year

First time I get rewarded for being patient, went to the amazon page for the book and noticed its free to me due to having "digital credit" for consolidating amazon deliveries on my choice of day of the week. Bought it!

Hello,
I am new to using the NanoVNA. In fact, I never knew what a vna was until 2 weeks ago. I bought this product to help test a pi filter networks and get some insight into some of my ham radio antennas. I built a circuit that has a pi filter network and was wondering about testing the matching of the network against the antennae load. I am new to that also. I understand I might need to make some adjustments to the coil by changing spacing. I have attached 2 pictures of the circuit. How can I use the nanovna to get some insight into this? It is VHF. Is this a good tool to use?

After some research, I think I might need to solder a SMA connector to the point where the xacto knife is pointing and measure some kind of signal to the sma connector on the extreme right? Is this the way top do it? S21?

I might have to solder wires to the sma connector and then solder to those to points on the board. If I did this, would I mess up my readings because of the non standard calibration plane. I would still leave the other elements of the circuit connected, namely the antennae out from the module. Would my readings be accurate. How would one do this without remaking a board with cfl connectors attached to it and SOLT items on the board?

Thanks,
Jeff

On 12/31/19 4:31 PM, chutton12000 wrote:

I suppose I have missed something simple.

???? Yes, you have.? Wander through the menu and you will find several ways to make measurements other than magnitude.? Lots of good stuff available on the wiki:

/g/nanovna-users/wiki/home

Hi Chuck,

Addressing the hardware vna first. You need to select a trace via the menu tree that displays the Smith Chart. Once you have the chart in display, the readout will be a real series impedance and a series L or series C. So this is KEY to obtain other than magnitude. Obtain a Smith chart display. Again, select via the menu tree:

DISPLAY, FORMAT, SMITH

The PC saver program is somewhat analogous. You must scroll down to the bottom and note there is a DISPLAY function selection. From there after selection a large array of drop down plotting features are provided and they are far more diverse than just magnitude.

Alan

I question your result of 51.2 Ohms.? My measurements on many cables come much closer to 50 Ohms.? It's probably a calibration issue; careful calibration results in quite accurate results.
All impedance measurements are a result of comparison with the LOAD used in calibration.
Bob On Tuesday, December 31, 2019, 04:44:10 PM PST, <reuterr@...> wrote:

Von: DJ7BA

Use magnifying glass to make sure if it really was RG58 - or was it perhaps RG59 ?

Hello Hans,
please see the attached photo of the coax cable: RG58_50-Ohm_IMG_1775.JPG

Then I measured a 100 cm RG316 50 Ohm coax cable.
This shows 51.2 Ohm, see attached: Coax_Lambda-div-8_RG316-100cm_51R2.png

Hence, the mystery is going on.

73, Rudi DL5FA

You aren't specific as to what you want to measure.? I have had excellent success measuring impedance, line length, characteristic impedance, SWR, passive components, resonance, and much more.
I tend to use the Smith chart display and sweep the frequency to see how the impedance changes.? Then I narrow the frequency span and measure other parameters.
The phase display can pinpoint resonance very well and of course is visible simultaneously with the Smith chart.
I can measure capacitors from under 1 pF to 1 microfarad more or less.? Resistors from milliohms to a few thousand ohms.? The vector impedance is displayed so I can see both R and X.
I also own the boat anchor type of VNAs and have hardly used them since getting my nano.
Feel free to ask how to do any measurement in particular.
Bob

Von: DJ7BA

Use magnifying glass to make sure if it really was RG58 - or was it perhaps RG59 ?

Hello Hans,
please see the attached photo of the coax cable: RG58_50-Ohm_IMG_1775.JPG

Then I measured a 100 cm RG316 50 Ohm coax cable.
This shows 51.2 Ohm, see attached: Coax_Lambda-div-8_RG316-100cm_51R2.png

Hence, the mystery is going on.

73, Rudi DL5FA

Any chance of a short summary?
I've been looking for comparisons of the nanoVNA to HP VNAs, Array So;utions VNA or the wonderful N2PK VNA.
Or for that matter a nice thorough review.

Chuck

Hi -

First, an apology. I have very limited eyesight so I often miss thimgs.

My big VNA is the N2PK with MyVNA software. It lets me scan impedance and many other things.

I've been using NanoVNA# with my nanoVNA but don't see a way to do anything other than magnitude measurements.
I've looked at NanoNA Saver but it seems to have the same issue.

I suppose I have missed something simple. If not, are there other options?

Chuck