开云体育

#92.2 : Our General Picture of [TheLeastVNA] - Update 2

Hello,

We corrected, completed, and just replaced our previous [92']
Figure of our General Picture of the 4-port that results to our
Virtual-Real 2-Port of Measurement-Load, respectively [92'],[92],
as follows:



in order to that be fully harmonized with our formulation [94]
of Virtual-Real 2-Port:



Sincerely,

gin&pez@arg

REFERENCES

[92'] : Our General Picture of [TheLeastVNA] - Update
24 December 2019
/g/nanovna-users/message/8648

[92]: Our General Picture of [TheLeastVNA]:
24 December 2019
/g/nanovna-users/message/8612

[94] : facupov in our sow : From our Real 4-Port to our Virtual-Real 2-Port - A Simple Proof
25 December 2019
/g/nanovna-users/message/8653


:92.2#

HI

I too spent the 3 bucks. I just received my NanoVNA about a week ago. I
have been reading this group for a couple of weeks now. It is nice to have
a lot of beginner information in one place.

FYI, my Nano that I bought on Amazon failed to charge. The blue LED would
flash for hours, then go on steady. It would not power on when I unplugged
the cable and switched it on. It would work okay while plugged in. I sent
it back for an exchange.

Looking forward to playing with my Nano. I want to try the TDR measurements
on my new antenna installation.

73
Randy, K7AGE



On Wed, Jan 1, 2020 at 1:47 PM Jim Allyn - N7JA <jim@...>
wrote:

On 1/1/20 11:35 AM, Jim Shorney wrote:

Normally I would agree with that, but for three bucks I'm happy to have

this easily accessible on my vintage kindle Fire as portable as the NVNA
is. Another THANKS! to Chris.

I agree! I too spent the 3 bucks, and I think it will be
convenient to keep on my phone.

On 1/1/20 11:35 AM, Jim Shorney wrote:

Normally I would agree with that, but for three bucks I'm happy to have this easily accessible on my vintage kindle Fire as portable as the NVNA is. Another THANKS! to Chris.

???? I agree!? I too spent the 3 bucks, and I think it will be convenient to keep on my phone.

On 1/1/20 11:29 AM, Klaus W?rner wrote:

Maybe you have the same bad cable as I. I played last year with the FA-VA5 and TDR. I had the same problem as you. I measured 76 Ohms. Then I built an impulse generator and measured the impedance with my oscilloscope. And what I had seen? Yes, this RG58 has really 76 Ohms.
My is from Comtex. Yours, too?

???? It does happen. Years ago I was building a matching/phasing harness for my 70cm ham satellite antenna, and I just couldn't get anything to work as it should.? I finally discovered that the coax I was using was mislabeled: it was actually 91 ohms characteristic impedance.? One of my coworkers took a picture of me while I was trying to figure out what was going on, and later, after I had figured it out, he presented the photo to me with the caption, "Alright, who slipped me the 91 ohm coax?"? I wish I still had that photo.? With the caption and the look on my face, it was priceless.

I ran this network and first calculated the L values from your schematic physical entries.

I get 66 nH and 38 nH. Reasonable.

Then I looked at what a 7 element Tchebychev filter with 0.1 dB ripple may look like if terminated both sides into 50 ohms. The passband cutoff is set to 150 MHz as I recall that was your pass goal and then seek attenuation. The design network is not to far off in values per your schematic..... L values of 75 and 83 nH and C values of 25 and 45 pF. Clearly there will be a disconnect in response performance as those coils in the photo are "knifed"... that is TUNED to reduce their inductance. And that does not quite make sense unless the pcb, parasitic and coupling all add into the response deviation from ideal. And that can happen!

I attached here the design response, the designed network and the response after I tuned your L's and set in your cap values per the schematic. These are the responses you may expect with the vna for S21 measure or CH0 to CH1 ratio and the S11 measure or return loss which is the so called CH0 or ONE port measurement where by the filter output is terminated into 50 ohms.

Have FUN. The moral here is to do some up front investigation of designs, back of the envelope stuff, before attaching the neat instruments.

Alan

On Wed, Jan 1, 2020 at 08:29 PM, Klaus W?rner wrote:

Maybe you have the same bad cable as I. I played last year with the FA-VA5 and
TDR. I had the same problem as you. I measured 76 Ohms. Then I built an
impulse generator and measured the impedance with my oscilloscope. And what I
had seen? Yes, this RG58 has really 76 Ohms.
My is from Comtex. Yours, too?

Hello Klaus,

Unfortunately I did not remember the copmany I bought from.

73, Rudi DL5FA

For giggles and grins I will run a quick analysis of this network. It is a 7 element and because of identical end C terminations I suspect a Tcheychev filter with equal terminations. Will see.

Alan

From David's iPad

On 1 Jan 2020, at 18:54, David J Taylor via Groups.Io <david-taylor@...> wrote:

?David,
What did you have attached to the unit for that test/screenshot?

Regards,
Chris
====================================

Oops, you wanted:

David

Thanks everyone for your helpful replies! These resources will be most useful to me.

Dave, my preferred learning method is actually reading! :) I’d be very interested in textbooks or other reading matter on the subject if you have any suggestions. The video link looks most useful though, and I’ll be viewing those videos.

Thanks again!
Randy
NC8U

Another situation that might cause an open at the far end, if the UHF antenna (hopefully) uses a N connector, make sure the fingers of the center conductor receptacle are not bent or even missing one or more legs. I once had a situation where the fingers where slightly flared and not making any contact with the center pin of the male plug. By carefully bending them back with long nose pliers solved the problem. This sometimes also happens on BNC female connectors.

For the graphs, just Right-Click on the graph you want to save, and a pop-up menu appears with the option to "Save Image" which is really nice

--
Regards,
Chris

Normally I would agree with that, but for three bucks I'm happy to have this easily accessible on my vintage kindle Fire as portable as the NVNA is. Another THANKS! to Chris.

73

-Jim
NU0C

On Wed, 01 Jan 2020 19:12:13 -0000
"mike" <pencoys@...> wrote:

There is nothing in the 'Book' that is not already published on the groups.io
site.
YMMV but I think I would prefer the groups.io resource.

On 1 Jan 2020 at 9:57, Birdman wrote:

On Wed, Jan 1, 2020 at 06:13 AM, Christoph Schw?rzler wrote:

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

Thanks, I was not aware kindle had windows and iOS apps! Bought, downloaded
and reading..... thanks.


--
Regards,
Chris

On Wed, Jan 1, 2020 at 01:44 AM, <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

Maybe you have the same bad cable as I. I played last year with the FA-VA5 and TDR. I had the same problem as you. I measured 76 Ohms. Then I built an impulse generator and measured the impedance with my oscilloscope. And what I had seen? Yes, this RG58 has really 76 Ohms.
My is from Comtex. Yours, too?

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

I have a new NanoVNA.? I also have a MiniVNA and a MetroVNA.? In the past I have utilized professionally the HP 8710 and 8711 VNA's, so I am not a new to the subject.? I've been lurking on this list for several months and am thoroughly confused by all the traffic and various postings.? It is hard to glean any substantial help from the random clutter of subjects.

Is there a composite website for the NanoVNA that categorizes, inventories or indexes, useful helps and information?? Random searching thru all the files doesn't seem to be the answer either.

For example:? There is an excellent website at It is focused on the Kenwood Ts-590 S and SG, HF transceivers.? The website options are well organized and explained.? It makes it more productive to glean out topics that might apply to one's particular product and situation.

A similar composite listing would be greatly useful for the NanoVNA users.?? BTW: The Mini and Metro users suffer from the same lack of such a website.

One current question I have and have not seen posted, but may have missed:?? Is there an Android app which would allow the Nano to be displayed on a larger tablet screen for more visual resolution and easier control?
Ray, W4BYG

There is nothing in the 'Book' that is not already published on the groups.io
site.
YMMV but I think I would prefer the groups.io resource.

I think the L and C measurements are WAY off!

Nominal capacitance is 100 pf/m, and nominal inductance is 250 nH/m.

73
Willi
OE1WKL

Von meinem Mobiltelefon gesendet

David,
What did you have attached to the unit for that test/screenshot?

Regards,
Chris
====================================

Just NanoVNA-saver, and Windows Win-shift-S, copied from the clipboard to IrfanView.

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

On Wed, Jan 1, 2020 at 07:16 PM, David Eckhardt wrote:

n Wed, Jan 1, 2020 at 5:46 PM Helmut Wabnig <hwabnig@...> wrote:

On Wed, 01 Jan 2020 09:08:16 -0800, you wrote:

Hello Helmut,

I measured at the 100 cm fake-RG58 coax cable L = 2.5 uH @355 KHz, C = 4.7 nF @195 KHz.

In a Calc sheet I entered SQRT(2.5E-6/4.7E-9) and got = 23.06 Ohm?

That could not be the wave resistance of the coax cable.

73, Rudi DL5FA

You measured at different frequencies?

Unfortunately the LC measuring principle varies the frequency for measuring.
I can not setup a specific frequency.

You see, measuring with the nanoVNA with the *Lambda/8* method has its advantages :-)

I think, I will stay with it.

73, Rudi DL5FA

Measure both L and C AT THE SAME FREQUENCY!

--

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