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Rainer,

If you remove power from the bias-tee, the LNA no longer works.
But it almost certainly does not short input to output,
and if it did it would not do so without adding extra loads to ground.

Unless it happens to be extremely fancy and have Jim's relay included in the package.

You need to remove the LNA somehow to measure the antenna with the nanovna.

Jerry, KE7ER

I believe the m stands for milli (1/1000).

Mark

*From:* Jim Lux ( jimlux@... )
*Sent:* Tuesday, October 6, 2020 9:44 AM
*To:* [email protected]
*Subject:* Re: [nanovna-users] Basic Question About Complex Impedance Numbers

On 10/6/20 4:25 AM, ed.jackson001@... wrote:

Hello all...

I have a dipole that I ran a sweep on with NanoVNA Saver, and a NanoVNA-H. When looking at the complex impedance at the closest point to resonance ('0' reactance), I get numbers like

56.3-j697m ohms (no 'ohm' symbol on my laptop).

What does the 'm' mean? I'm assuming that means the reactance part is very close to '0'. Is that correct, or am I all wrong?

milli.? so it's 0.697 ohms.

On 10/6/20 8:11 AM, Rainer wrote:

Hi,
I was thinking about this DC Blocks.
If I understand correctly those DC Block block the DC current and without DC current my Low Noise Amplifier does not work, correct ?
So if that is the case, why not just turn Bias Tee OFF and I can measure through ... right ?
BTW I ordered the pack of two. For what do I need them if above is OK ?
Rainer

if your LNA is one that has a relay to bypass it when it's off, then yes, turning off the power would be what you need.

Hi,

I was thinking about this DC Blocks.

If I understand correctly those DC Block block the DC current and without DC current my Low Noise Amplifier does not work, correct ?

So if that is the case, why not just turn Bias Tee OFF and I can measure through ... right ?

BTW I ordered the pack of two. For what do I need them if above is OK ?

Rainer

On Tuesday 06 October 2020 08:32:50 am DougVL wrote:

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

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.

In that case, you will eventually want to use the NanoVNA on other antennas as well. It will be REALLY worthwhile to get a few connector adapters. I have gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in pairs or sets of 4, with combinations of the 4 possible gender setups. Male to male, male to female, and so on. You may get one you don't need, but it's cheaper to get the sets. And later on, you will wish you had another one! Even if it is to help a friend with his project instead of your own. Amazon has many sellers of various sets and assortments, and of course there are usually reviews to help decide if their quality is good enough. And of course there are many more sources on ebay and aliexpress - which might be easier or better for some people outside of the USA or where Amazon might not ship to.

Amazon has enough money, they don't need any more.

I got a pair of SO239 and BNC adapters from R&L when I ordered my H4, and figure that should cover my needs nicely. I've seen others post links to these particular parts recently in here. $3.95 each.


--
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

Very Nice piece of software - Thank you to OneOfEleven

Granted that I've spent the last couple of days coming up to speed on the NanoVNA and the other PC apps for it before I found this a few hours ago so I've had a lot of practice - but I have to say I found it very intuitive and easy to use. Just have to puzzle out the Markers and see if there is a way to change the Red Line for VSWR . . .

Thanks Again - Much Appreciated

Ross VK2ATA

On 10/6/20 4:25 AM, ed.jackson001@... wrote:

Hello all...
I have a dipole that I ran a sweep on with NanoVNA Saver, and a NanoVNA-H. When looking at the complex impedance at the closest point to resonance ('0' reactance), I get numbers like
56.3-j697m ohms (no 'ohm' symbol on my laptop).
What does the 'm' mean? I'm assuming that means the reactance part is very close to '0'. Is that correct, or am I all wrong?

milli. so it's 0.697 ohms.

On Thu, Oct 1, 2020 at 01:43 PM, Danny K5CG wrote:

My post wasn't intended to start that war over again, but to acknowledge that
it was already fought, and won.

Won by the SMA'ers evidently, and rightfully so in this application.

Most of my adult life has been spent working on radar systems, from 1 to 22 GHz. The determining factor in whether SMA or N connectors are used at various points in these systems is the power level at the connector and the robustness of the supporting panel/component.

SMA's are the correct connector to be using on these small VNAs.

--
John AE5X

On Tue, Oct 6, 2020 at 02:32 PM, DougVL wrote:

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

In that case, you will eventually want to use the NanoVNA on other antennas as
well. It will be REALLY worthwhile to get a few connector adapters. I have
gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in
pairs or sets of 4, with combinations of the 4 possible gender setups. Male
to male, male to female, and so on. You may get one you don't need, but it's
cheaper to get the sets. And later on, you will wish you had another one!
Even if it is to help a friend with his project instead of your own. Amazon
has many sellers of various sets and assortments, and of course there are
usually reviews to help decide if their quality is good enough. And of course
there are many more sources on ebay and aliexpress - which might be easier or
better for some people outside of the USA or where Amazon might not ship to.

I was surprised to find that I needed (well, wanted) an adapter with female
SMA to female UHF (SO-239) - it was for testing a mobile 5/8 wave 2-meter
whip antenna. Of course, a "double SO-239" 'barrel' connector adapter would
help instead, but add weight and bulk and a little inconvenience. After you
become well accustomed to your VNA, you may find that you want to test other
CB antennas, and they may have permanently attached PL-259's. You might be
helping friends with their problems, as well as using it for your own station.
You might even want adapters for type F connectors for television antenna
checking.
I have a clear plastic box with about a dozen compartments, for organizing and
storing my many adapters. It is very useful, almost a necessity.

Congratulations on getting your license! There is so much you can do with
amateur radio. And so much that you can enjoy learning!

Doug, K8RFT

Thank you! I will definitely get them sooner or later, the question was more about possibility to do it once or twice, because my local store does not sell them and there is a CB event this friday, so I wanted to have the dipole ready by then.

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

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.

In that case, you will eventually want to use the NanoVNA on other antennas as well. It will be REALLY worthwhile to get a few connector adapters. I have gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in pairs or sets of 4, with combinations of the 4 possible gender setups. Male to male, male to female, and so on. You may get one you don't need, but it's cheaper to get the sets. And later on, you will wish you had another one! Even if it is to help a friend with his project instead of your own. Amazon has many sellers of various sets and assortments, and of course there are usually reviews to help decide if their quality is good enough. And of course there are many more sources on ebay and aliexpress - which might be easier or better for some people outside of the USA or where Amazon might not ship to.

I was surprised to find that I needed (well, wanted) an adapter with female SMA to female UHF (SO-239) - it was for testing a mobile 5/8 wave 2-meter whip antenna. Of course, a "double SO-239" 'barrel' connector adapter would help instead, but add weight and bulk and a little inconvenience. After you become well accustomed to your VNA, you may find that you want to test other CB antennas, and they may have permanently attached PL-259's. You might be helping friends with their problems, as well as using it for your own station.
You might even want adapters for type F connectors for television antenna checking.
I have a clear plastic box with about a dozen compartments, for organizing and storing my many adapters. It is very useful, almost a necessity.

Congratulations on getting your license! There is so much you can do with amateur radio. And so much that you can enjoy learning!

Doug, K8RFT

On Mon, Oct 5, 2020 at 09:19 PM, OneOfEleven wrote:


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

======================================================

I've used libusb with SDR devices and it can sometimes be a bear to get configured properly, requiring the user to manually place the correct libusb0 or libusb1 driver in the correct Windows System location.

I hope during beta testing that Jan is able to work out any potential driver installation issues.

- Herb

Thank you very much Christian. That was what I suspected, but wanted confirmation.

Ed

"m" simply means "milli". I.e., 56.3 - j*0.697 ohms.

Hello all...
I have a dipole that I ran a sweep on with NanoVNA Saver, and a NanoVNA-H. When looking at the complex impedance at the closest point to resonance ('0' reactance), I get numbers like

56.3-j697m ohms (no 'ohm' symbol on my laptop).

What does the 'm' mean? I'm assuming that means the reactance part is very close to '0'. Is that correct, or am I all wrong?

Thank you for your time.

Thank you Larry!

There’s a few references here.


Application notes 3 and 4 are particularly informative on this. Generally
the Keysight application notes are useful.

Great set of references. In addition to Dave's HP application note links, there are more here: .

The 8510 documentation is especially worthwhile because its UI seems to have been one of the main inspirations behind the NanoVNA, or at least the -V2 model. Even better if you can track down the training seminar binder that HP provided to 8510 customers. I've never seen a .PDF of that one, which is a shame.

The book by Dr Joel Dunsmore, who is a Keysight employee, is quite
informative, but is heavy going mathematically, and a typical price of a
professional text book - ie 2-4 times the cost of a nanoVNA.

Joel's book has a brand-new 2nd edition, 25%+ longer ( ). I wouldn't say that it's too mathematically-heavy, just that the math is there for those who need to delve into it. Nice resource for anyone who has either progressed beyond the initial fundamentals or would like to do so.

There is a similar book from Michael Hiebel of Rohde & Schwarz ("Fundamentals of Vector Network Analysis", ). Fortunately there are used copies for sale at less than the $375 quoted for a new hardcover. You probably don't need both the Hiebel and Dunsmore books, but if you're interested in this stuff, you should own at least one of them IMO.

-- john, KE5FX

Yes, using binary data transfer, USB-CDC is no problem at all. But this is a completely restarted project. Jan developed this project completely independently. We can consider compatibility in the future process, but please don't put any pressure on Jan now. Although the APP currently provided by Jan is not perfect, it works very well and already includes simple spectrum analyzer and signal generator functions. It can also be manually configured and firmware upgraded, which is a very good innovation and experiment.

First let me add that the load standard does not have to be ideal, it only has to be known. You can reformulate the SOL calibration to account for a non-ideal load. The same of course applies to short and open standards [1]. If you use a SOL calibration where the load is assumed to be ideal (such as in NanoVNA firmware), any reflections from the load are erroneously attributed to the directivity error (e00, ed, depending on which literature you use). I.e., the calibration assumes that anything measured as reflected wave while the load standard is connected comes from the VNA coupler's limited directivity. Thus, any unaccounted for reflections from the load itself distort the e00 error term.

You can see (from Doug Rytting's presentation [2], page 13) that e00 is subtracted from the measured S11 while calculating the actual (corrected) S11. This means that in an SOL calibration assuming an ideal load, this load measurement "sets the zero reading" for subsequent measurements. Quantitatively, the error has to be explored with uncertainty calculations, but qualitatively it's apparent that your load standard should be better than the directivity error that you want to correct, otherwise you'd make the measurement worse. (I don't know the uncorrected directivity of the NanoVNA.)

However, as stated in the beginning, if you know your load, you can account for non-idealities by using, e.g., NanoVNASaver.

Regards
Christian

[1] The PC application NanoVNASaver allows you to enter the calibration coefficients for non-ideal standards. The NanoVNA firmware (I only checked hugen's version) assumes ideal loads and shorts and a fixed (non-configurable) fringe capacitance of 50 fF for the open.
[2]

On Mon, 5 Oct 2020 at 22:41, <ray@...> wrote:

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?

As a rough guide, you need the load to have a return loss of 10 dB higher
than what you are measuring to get a measurement uncertainty of 1 dB. So a
30 dB return loss load will enable measurement of a DUT with a return loss
of 20 dB.

The usual method of measuring the quality of the calibration is to measure
the variation of return loss of a precision airline. A Beatty standard,
which is an airline with a step in its impedance, is also useful. The
theoretical response can be calculated from physical measurements.

To the best of my knowledge, the NanoVNA firmware doesn’t allow one to
specify the electrical parameters of the calibration standards, although
some external software, such as nanoVNA Saver, does implement SOLT
calibration properly. The significance of that will depend upon the
frequency and the characteristics of the standards.

I have an Agilent 85054B N calibration kit (new cost $21,756). It is
capable of very high accuracy, but would give particularly poor results
with a NanoVNA as the offset delays of the standards are quite long (over
63.07 ps on the male short and 57.99 ps on the male open ).

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.

There’s a few references here.



Application notes 3 and 4 are particularly informative on this. Generally
the Keysight application notes are useful.

The book by Dr Joel Dunsmore, who is a Keysight employee, is quite
informative, but is heavy going mathematically, and a typical price of a
professional text book - ie 2-4 times the cost of a nanoVNA.

Thanks and 73's,
Ray
KN4SK

Dave, G8WRB.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

Hey Alan,

Thanks, I got it downloaded and installed. This appears to be for seeing uncertainty given a specific model VNA and cal kit. It's quite interesting but if I had my own cal kit, how might I estimate the uncertainties of that? Suppose I have a load standard that comes out at 52 ohms and some nH of inductance and I want to set an upper frequency limit. Maybe there are some rules of thumb. Or maybe I've overlooking a way to use that Keysight spreadsheet.

Thanks,
Ray