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Re: New open source VNA released - excellent performance claimed

 

USB CDC can go at 1MByte a second without any problem really, though using libUSB is good too.

So at 1MByte/sec USB CDC throughput you can have 38000 points a second assuming 26 bytes per point (6 byte int freq, 8 byte S11 I/Q, 8 byte S21 I/Q). So using USB-CDC wouldn't be a bottle neck unless you wanted to go faster than 38000 points/sec.
Re: New open source VNA released - excellent performance claimed

 

Hello Herb, this 6GHz VNA is a brand new VNA independently designed by Jan. USB needs a faster speed to ensure that 1000 scan points can be transmitted per second. Jan uses a more efficient libusb communication. Although we can also use libUSB to drive the USB-CDC on NanoVNA, all NanoVNA software is based on serial communication, so the USB communication module must be modified to achieve compatibility.

This is Jan's first attempt to use QT to develop VNA software. We promote the progress of the project with the purpose of learning. We believe that through continuous learning and communication, the software can achieve better development.
Re: SOLT Error Theory #calibration

 

I will contact Keysight and find out when we can see a fix.

Thanks for the alert.
Re: SOLT Error Theory #calibration

 

Unfortunately, the Keysight website is broken. Cannot download either
32- or 64-bit software...

On 2020-10-05 18:54, alan victor wrote:

Here you go... Keysight has taken the paper calculator and expanded it quite a bit!

Now you can do all you want and more to answer your query.

Have FUN. Alan



Re: SOLT Error Theory #calibration

 

Here you go... Keysight has taken the paper calculator and expanded it quite a bit!

Now you can do all you want and more to answer your query.

Have FUN. Alan

Re: SWR measurement of CB antenna with PL-259 #newbie

 

W5SWL is a good person to buy adapters from. Prices are reasonable and he has just about everything. eBay store or .

73

-Jim
NU0C

On Mon, 5 Oct 2020 09:59:02 -0700
"Jim Lux" <jimlux@...> wrote:

On 10/5/20 8:12 AM, vitovsky.petr@... wrote:
Hello,
I ordered NanoVNA and it should arrive this week. I'm building wire dipole for my CB and I would like to measure its SWR. The problem is that I will be using the PL-259 connector and the NanoVNA I ordered has only SMA. The PL connector is not attached to the coax (RG-58) yet. Is it possible to measure the SWR just by attaching SMA to the coax
provisionally and replacing it with the PL when I'm done? Or do I have
to buy SMA to PL adapter?

Get yourself some SMA to PL-259 adapters (actually, what you probably
want is SMA to SO-239 jacks..

There's two ways to go about it.

a one piece adapter (I got a set of all 4 gender combinations for <$10
from amazon - )

A short cable with SMA on one end and PL-259 (I had one from my mobile
rig installation a while ago, about 12" long).

if you go on amazon and search "SO-239 SMA pigtail" you'll get a bunch..
Looks like a pair of 6" ones is $10


I prefer the pigtail - cables with PL-259s tend to be fairly stiff, so
having some inches of small diameter cable in between reduces the stress
on the VNA.. you really, really do NOT want something like 0.405" coax
directly connected to the VNA - you might snap the connector off the board.


Thanks for any advice, as a newbie I really appreciate it.
Re: SOLT Error Theory #calibration

 

Hi Ray,

The simple answer to your query... It shows up in the uncertainty.
There is an excellent treatment of the calculations provided by hp that was presented at one of their seminars... years ago.
They provided each attendee with an uncertainty calculator slide rule. I will see if I can find its part number.


Alan
SOLT Error Theory #calibration

 

Hi, new member here. I'm a reasonably experienced Microwave engineer and will add a NanoVNA to my bench soon. In the process of reading about this VNA I've become interested in better understanding the theory behind SOLT (and TRL) cal standards. I've primarily used commercial SOLT cal kits or TRL of my own making.

For example, if my SOLT Load standard is 10dB vs 20dB return loss, what are the consequences? How do I determine how good is good enough for each standard?

I realize this might not be in the bull's-eye of interest for the typical NanoVNA user but there are clearly some knowledgeable folks in this forum. If anyone is aware of a good text on this, a reference would be appreciated.

Thanks and 73's,
Ray
KN4SK
Re: Newbee with Nano VNA device

Rainer
 

Thanks everybody for the tips.

Rainer
Re: Newbee with Nano VNA device

 

Hey Rainer, it's what I would use.. Says package of two in add, I
noticed one guy reported he only received one. Nobody else reported
that however. Probably an error on the marketers part.
Interestingly one reply indicated he measured up to 9GHz with little
to no insertion loss, although specs say 6GHz.
I've used higher quality ones (much higher cost Pasternack, and
others, rated to 18GHz) up as high as 24GHz, with no adverse effects.

Just be careful to not place too much lateral pressure on the longer
connection to preclude damage to the circuit board SMA soldered
connections. By the way, if you have a SAA-2N (N-connectors) there are
also DC Blocks for N.

Regards ..... Ted (KD7AQO)

----------------------------------------From: "Rainer"
To: [email protected]
Cc:
Sent: Monday October 5 2020 12:23:18PM
Subject: Re: [nanovna-users] Newbee with Nano VNA device

Thanks everybody.

I guess this is what I need Mute This Topic:

Links:
------
[1]

/>
Right ?

Rainer


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Re: Newbee with Nano VNA device

 

Make sure you select the correct device, that web link could be for any of 6 different devices.
I'd probably get the SMA-MF(50khz-8ghz)
Perhaps somebody else has a better suggestion.

Jerry, KE7ER

On Mon, Oct 5, 2020 at 12:23 PM, Rainer wrote:


Thanks everybody.

I guess this is what I need

Right ?

Rainer
Re: Newbee with Nano VNA device

 

I have yet to need a DC block.
If I did, would likely just put down something like
a $0.01 0805 N0G 0.01uF cap on the device I was inspecting.
Or cut an SMA cable in half, add an SMA jack at the end of the coax with a series cap.

Size the cap to be reasonably low reactance at the lowest frequency of interest,
where reactance_in_ohms = 1/(2*pi*Hertz*Farads)
I believe that any reactance in the cap (within reason, keep it under 50 ohms),
be it capacitive or inductive, would get corrected for by the calibration step.
So maybe use your VNA to see if the cap has some serious inductive reactance
at the highest frequency of interest.

Then check out something that does not have a DC issue using the VNA,
comparing results with the DC block in place and without, re-calibrating for each.
Verify that you get the same readings.

For saving the VNA's SMA connectors from wear,
I just leave two short SMA-to-SMA cables in place on my VNA.
The only connector that will wear out is the far end SMA connector of each cable.
The short cables also prevent mechanical stress on the VNA circuit board.


The DC blocks from Minicircuits or Pasternack are in the $50 to $150 price range.
I'm sure there are cases where these are a good idea,
but I'm just puttering around here with a $50 vna.
I can afford a slight risk of blowing out the front end.

However, if you do want to look like a professional,
here's two DC blocks at $20 total on Amazon,

You probably want the SMA-MF(50khz-8ghz).
They claim to have an SMA-MF(DC-6ghz), I have no idea how
you would build a DC block that allows signals through down to DC.
Didn't look hard, but haven't yet seen anything cheaper than that $20 for two.
Except the $0.01 for an 0805 cap.

Jerry, KE7ER

On Mon, Oct 5, 2020 at 11:32 AM, Ted Chesley wrote:
Jerry, Simple solution if worried about application of DC voltages to
the ports, is to use an inline SMA-M to SMA-F DC Block available from
Amazon for anywhere from $7-10 US for a pack of two on up to $45 or so
from higher end manufacturers. Rated loss is a few 10ths of a dB to
6GHz, or in the case of Nooelectric's piece, 8GHz, but it's $20 ea. If
you review these, read the customer feedback, generally positive from
hams and other engineers.
This serves a couple purposes : blocks DC voltage as well as provides
an extension to save the instrument connector SMA threads. I assume if
calibrated once installed, any impedance offsets will be zero'd out. I
thought I had one for instrumentation but can't find it to check.
Anybody else have any experience with these?

Regards, Ted (KD7AQO)
Re: Newbee with Nano VNA device

Rainer
 

Thanks everybody.

I guess this is what I need

Right ?

Rainer
Re: Newbee with Nano VNA device

 

Jerry, Simple solution if worried about application of DC voltages to
the ports, is to use an inline SMA-M to SMA-F DC Block available from
Amazon for anywhere from $7-10 US for a pack of two on up to $45 or so
from higher end manufacturers. Rated loss is a few 10ths of a dB to
6GHz, or in the case of Nooelectric's piece, 8GHz, but it's $20 ea. If
you review these, read the customer feedback, generally positive from
hams and other engineers.
This serves a couple purposes : blocks DC voltage as well as provides
an extension to save the instrument connector SMA threads. I assume if
calibrated once installed, any impedance offsets will be zero'd out. I
thought I had one for instrumentation but can't find it to check.
Anybody else have any experience with these?

Regards, Ted (KD7AQO)

-----------------------------------------From: "Jerry Gaffke via
groups.io"
To: [email protected]
Cc:
Sent: Monday October 5 2020 10:42:54AM
Subject: Re: [nanovna-users] Newbee with Nano VNA device

Interesting.
Thanks for bring this up!

Looking at the schematic on page 10 of the pdf pointed to by the
reddit post,
I'd guess the first resistor to burn due to DC injected into the TX
SMA port would be R14.
Current there is roughly Vtx/(49+56), and power at R14 is I**2 * R =
(Vtx/105)**2 * 56 Watts
Assuming R14 is good for 1/10 Watts before it burns out:
0.10 = (Vtx/105)**2 * 56
sqrt(0.10/56) = Vtx/105
Vtx = 105 * sqrt(0.10/56) = 4.43 Volts DC max into the TX SMA.
A thorough analysis of that resistor network might bring the max DC
voltage even lower.

On the RX SMA port, first to go is the 100 ohms at R24, placed
directly across the port.
0.10 = Vrx**2/100
0.10*100 = Vrx**2
Vrx = sqrt(10) = 3.16

So if DC exceeds 3 volts into either port, a blocking cap should be
used
to prevent burning out a resistor in the nanovna.

Given all the blocking caps further back at the SA612A mixers and
Si5351 clock generator,
I believe the nanovna should still give accurate results with a DC
bias on the TX and/or RX port.

My nanovna has RFI covers over those resistors,
the figure of 0.1 Watts max per resistor assumes 0805 resistors.
If it's 0603 resistors, then it's 0.063 Watts max per resistor,
and you'd best keep DC voltage below sqrt(0.063watts*100ohms) = 2.5
Volts.

Jerry, KE7ER

On Mon, Oct 5, 2020 at 09:07 AM, Carol KP4MD wrote:
> A schematic diagram posted a similar thread on Reddit
> Mute This Topic:

Links:
------
[1]


/> > shows there is a DC current path through resistors on the
NanoVNA ports.
> You can possibly damage the NanoVNA ports if you apply a DC voltage
from the
> bias T to them. You need to attach a DC blocking capacitor in
series with any
> connection to the NanoVNA on which a DC voltage is present.
>
> Carol
>


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View/Reply Online (#17924): </br<></a><a href=
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/> -=-=-
Learn about the NanoVNA in the following forum areas:
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Re: Newbee with Nano VNA device

 

I agree with Jerry. Use an appropriate capacitor for RF such as ceramic or mica, not electrolytic or paper.

Carol
Re: Newbee with Nano VNA device

 

Interesting.
Thanks for bring this up!

Looking at the schematic on page 10 of the pdf pointed to by the reddit post,
I'd guess the first resistor to burn due to DC injected into the TX SMA port would be R14.
Current there is roughly Vtx/(49+56), and power at R14 is I**2 * R = (Vtx/105)**2 * 56 Watts
Assuming R14 is good for 1/10 Watts before it burns out:
0.10 = (Vtx/105)**2 * 56
sqrt(0.10/56) = Vtx/105
Vtx = 105 * sqrt(0.10/56) = 4.43 Volts DC max into the TX SMA.
A thorough analysis of that resistor network might bring the max DC voltage even lower.

On the RX SMA port, first to go is the 100 ohms at R24, placed directly across the port.
0.10 = Vrx**2/100
0.10*100 = Vrx**2
Vrx = sqrt(10) = 3.16

So if DC exceeds 3 volts into either port, a blocking cap should be used
to prevent burning out a resistor in the nanovna.

Given all the blocking caps further back at the SA612A mixers and Si5351 clock generator,
I believe the nanovna should still give accurate results with a DC bias on the TX and/or RX port.

My nanovna has RFI covers over those resistors,
the figure of 0.1 Watts max per resistor assumes 0805 resistors.
If it's 0603 resistors, then it's 0.063 Watts max per resistor,
and you'd best keep DC voltage below sqrt(0.063watts*100ohms) = 2.5 Volts.

Jerry, KE7ER

On Mon, Oct 5, 2020 at 09:07 AM, Carol KP4MD wrote:
A schematic diagram posted a similar thread on Reddit

shows there is a DC current path through resistors on the NanoVNA ports.
You can possibly damage the NanoVNA ports if you apply a DC voltage from the
bias T to them. You need to attach a DC blocking capacitor in series with any
connection to the NanoVNA on which a DC voltage is present.

Carol
Re: SWR measurement of CB antenna with PL-259 #newbie

 

Thanks for advice, just like Jerry suggested, I could for instance use alligator clips. I should have been more precise and say that the NanoVNA came with a short cable with SMA on both ends and I wanted to attach the coax to that, so snapping the connector of the board won't be an issue.

BTW I got my license few days ago, OK9PVV here :) I just don't have HF TRX yet, so I just wanted to experiment with my CB a bit.
Keysight Webinar on "Network Analyzer Fundamentals"

 

The following message was previously posted to the user group for the NanoVNA -F. It is being reposted here as a courtesy to the owners of any of the other versions of the NanoVNA.

If you recently purchased a NanoVNA -F, or any of the NanoVNA's for that matter, and you're waiting for it to arrive or you're trying to figure out how it works, what you can do with it or what all the features really mean; here is an excellent free webinar that is available on-line and on-demand from Keysight Technologies. The name of the webinar is "Network Analyzer Fundamentals" and it's presented by Keysight Product Marketer Mr. Matt Campbell. The running time is 45 minutes. To gain access to this webinar simply visit this website and search for the "Network Analyzer Fundamentals" webinar. There is a Search box. When the webinar comes up, simply click in the "Watch Now" box and the webinar will start.

I have been in contact with both the Marketing and Legal Departments at Keysight Technologies and have been assured that this webinar is available to the general public and to anyone who is interested in watching it. I found it to be an excellent source of information with pictures, graphics and movies that presents the fundamentals of Network Analysis is five parts: (1) What is a Network Analyzer, (2) Transmission Lines and S-Parameters, (3) Network Analyzer Block Diagram, (4) Network Analysis Measurements and (5) Calibration and Error Correction. Even though these topics are presented for the Keysight line of Network Analyzers, these are the basics and fundamentals and they apply to ANY Network Analyzer.

After the webinar, don't forget to visit the "resources" listed in the Resource Box. There you can download the webinar slides, visit a marvelous webpage on "Keysight Network Analysis" and obtain a download of an application note (16 page PDF) that covers all the topics in this webinar and then some. It is an excellent document to start your Network Analysis Reference Library.

Thank you everyone and enjoy your NanoVNA, no matter which kind or where it came from.
Re: SWR measurement of CB antenna with PL-259 #newbie

 

I made up a couple cables about 2 feet long with RG-316. One has an SMA on
one end and a BNC on the other end. Another has SMA's on both ends. Greatly
reduced chance of damaging the SMA on the NanoVNA with those cables.

73, Zack W9SZ

On Mon, Oct 5, 2020 at 12:33 PM <david.hostetler@...> wrote:

Having a really hard time imagining how you would "provisionally" attach
the nanoVNA to the coax. I highly recommend getting an adapter or pig tail.
I have purchased adapters and jumper cables from Amazon and it has been
about 50/50 hit or miss on quality and being able to do the job. BNC
connectors are particularly bad where I have had them not really mate well
because of machining burrs and most don't connect the outer shield properly
because the inside bore of the female is too large and/or the fingers on
the male have no springiness and fail to contact the inner bore on the
female - the shield/ground reins top only connecting through the bayonet
pins, maybe OK for video, but not so much for RF.

I have had good luck with R and L Electronics in Ohio, where a UHF female
to SMA male adapter is $3.95.

Also, if you test with the PL259 installed, you confirm the integrity of
your soldering work and you are equipped to re-check the antenna at any
time you have doubts or concerns.

Finally - If you have fun on CB, be sure to look into getting a ham
licence, Technician isn't too hard and your options are much wider.





<>
Virus-free.
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Re: SWR measurement of CB antenna with PL-259 #newbie

 

On 10/5/20 10:32 AM, david.hostetler@... wrote:
Having a really hard time imagining how you would "provisionally" attach the nanoVNA to the coax.
clip leads from a SMA connector to the coax (either bare, or with PL-259 attached..


I highly recommend getting an adapter or pig tail. I have purchased adapters and jumper cables from Amazon and it has been about 50/50 hit or miss on quality and being able to do the job.

Or, you can spend $20 at HRO, and they've got several of SO-239 SMA jumpers.

COMET-NCG part # HS-05
ABR Industries, 23316-SM-SO-6 or -3


BNC connectors are particularly bad where I have had them not really mate well because of machining burrs and most don't connect the outer shield properly because the inside bore of the female is too large and/or the fingers on the male have no springiness and fail to contact the inner bore on the female - the shield/ground reins top only connecting through the bayonet pins, maybe OK for video, but not so much for RF.
I have had good luck with R and L Electronics in Ohio, where a UHF female to SMA male adapter is $3.95.
Also, if you test with the PL259 installed, you confirm the integrity of your soldering work and you are equipped to re-check the antenna at any time you have doubts or concerns.
Finally - If you have fun on CB, be sure to look into getting a ham licence, Technician isn't too hard and your options are much wider.
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