Re: Measurement correction for Zc Coax caracteristic Impedance
Hi Dave
DiSlord coax function seems using Zc = 1/(4*fr*C0) ,
fr= is the first resonance frequency with open terminaison it's around 1.7Mhz measured by NANoVNA.
C0 = capacitance value at lower frequency around 50Khz to 100Khz measured by NanoVNA.
it gives a good value 51.7 Ohm around 1Mhz ,
but At 14.1 Mhz Zc changes a bit to 53 Ohm , and this impedance circle method seems sligthly better using around 50 Ohm terminaison load and frequency domaine around 14.1Mhz as explained in my last messages.
73's Nizar
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Re: Measurement correction for Zc Coax caracteristic Impedance
I wonder how the "short / open" method compares using Zc = SQRT [L / C] ? Of course, that will introduce losses due to theoretical infinite SWR. Dave - W?LEV On Fri, Apr 4, 2025 at 2:37?PM Team-SIM SIM-Mode via groups.io <sim31_team= [email protected]> wrote: Hi
below what i have measured on smith graph with my 25m length of RG213
coax cable with a NanoVNA H4
With Dislord function and no terminaison : it gives Z0=51.7 Ohm , it do
not change with frequency's , based on low frequncy's measurement < 1.7 Mhz
with a 50.3 ohm resistor Coax terminaison, Smith graph gives a nice
centered little circle for 53 Ohm renormalized impedance graph, ( 52 Ohm
and 54 Ohm gives sheefted circles of center ) , 53 Ohm seems to be the
good Z0 value for around 14.100 Mhz frequency's and not 51.7 Ohm as
calculated by Dislord function,
This nice and relatively more accurate method need a 6X Zoom on smith
graph , why not to add this option on the future H4 firmware ?
see sceenshoots attached
73's Nizar
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: Measurement correction for Zc Coax caracteristic Impedance
Hi
I think that this method of small circles centered with the renormalized impedance at the center of the Smith graph, must bring two advantages compared to that used by the DiSlord method:
1) we are rather in progressive wave and almost no standing wave, that is to say our area of ??interest during our antenna measurements close to SWR = 1.0,
2) secondo the measurements are rather made around the frequency of interest 14.100 Mhz a span of 4Mhz.
just it is desirable to have a graphic zoom of 8x of the Smith graph to further refine the value of Z0.
73s Nizar
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Re: Measurement correction for Zc Coax caracteristic Impedance
Hi
below what i have measured on smith graph with my 25m length of RG213 coax cable with a NanoVNA H4
With Dislord function and no terminaison : it gives Z0=51.7 Ohm , it do not change with frequency's , based on low frequncy's measurement < 1.7 Mhz
with a 50.3 ohm resistor Coax terminaison, Smith graph gives a nice centered little circle for 53 Ohm renormalized impedance graph, ( 52 Ohm and 54 Ohm gives sheefted circles of center ) , 53 Ohm seems to be the good Z0 value for around 14.100 Mhz frequency's and not 51.7 Ohm as calculated by Dislord function,
This nice and relatively more accurate method need a 6X Zoom on smith graph , why not to add this option on the future H4 firmware ?
see sceenshoots attached
73's Nizar
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Re: NanoVNA H FW 1.0.53 Display Intermittent
I have this problem even with my recently purchased NanoVNA. Sometimes when I switch on, the screen is blank. If I switch off and switch on once again, usually it becomes OK. The problem recurs again during the next power on sometimes. Occasionally I have to switch on and off a couple of times or more to get the screen visible. Otherwise there is no problem with the functioning of the NanoVNA. Battery gives good charge retention. 73 Jon, VU2JO On Thu, Apr 3, 2025 at 10:59?PM k6whp via groups.io <k6whp= [email protected]> wrote: Have an old NanoVNA H with the above FW whose display is intermittent.
More specifically, the menu turns off and on or will revert to the main
menu.
I have tried to do the touch cal and touch test with no success.
Appreciate any remarks on the subject; resetting the unit, etc.
Thanks in advance.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: NanoVNA H FW 1.0.53 Display Intermittent
John,
Thank you for your advice; I think that is the reason for the fault.
I tried that and operated the unit outside of the case and it seemed to work a little better but the menu still flickered and jittered. I also noted that, after a full charge, the battery discharged rapidly -- after about 10 minutes of use. Apologize for not searching the group for an answer, but what battery could be used and how would it be replaced?
Thank you again.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: NanoVNA H FW 1.0.53 Display Intermittent
William,
Also check for battery swelling causing pressure on the display.
--John Gord
toggle quoted message
Show quoted text
On Thu, Apr 3, 2025 at 10:29 AM, k6whp wrote:
Have an old NanoVNA H with the above FW whose display is intermittent. More
specifically, the menu turns off and on or will revert to the main menu.
I have tried to do the touch cal and touch test with no success. Appreciate
any remarks on the subject; resetting the unit, etc.
Thanks in advance.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
Internally-matched power transistors use the internal bond wires as high-Q inductive elements. In conjunction with MOS capacitors they are used to build matching networks inside the package to bring the sub- to few-Ohm transistor impedances to something more manageable, or in some cases directly to 50 Ohm, at the device leads. The number of wires and their length, height and spacing determine their values, so are tweaked for tuning.
The devices' parasitic capacitances are absorbed into the matching network, making a useful element out of what was a hindrance.
73, Don N2VGU
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Re: NanoVNA H FW 1.0.53 Display Intermittent
William,
This might be due to the case pressing on the touchscreen
Try loosening the mounting screws or perhaps adding thin washers for spacing.
--John Gord
toggle quoted message
Show quoted text
On Thu, Apr 3, 2025 at 10:29 AM, k6whp wrote:
Have an old NanoVNA H with the above FW whose display is intermittent. More
specifically, the menu turns off and on or will revert to the main menu.
I have tried to do the touch cal and touch test with no success. Appreciate
any remarks on the subject; resetting the unit, etc.
Thanks in advance.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
NanoVNA H FW 1.0.53 Display Intermittent
Have an old NanoVNA H with the above FW whose display is intermittent. More specifically, the menu turns off and on or will revert to the main menu.
I have tried to do the touch cal and touch test with no success. Appreciate any remarks on the subject; resetting the unit, etc.
Thanks in advance.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
Re: NANO VNA H4 , Implausible measurement results?
Hi, Brian,
I still have mine with the matching speaker. Mine is an NC-183, not an NC-183D. Like you, I really loved that thing. Even now, the sight of it here brings back good memories.
But I haven't used it for awhile as I've been using an R-388 I built up from parts in the mid-'70s.
Even more, I use a Halli S-40B, a good compromise between weight and performance. The weight matters more to me at age 82 than is did a few decades ago.
73,
Maynard
W6PAP
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On 4/3/25 08:54, Brian Beezley wrote: On Thu, Apr 3, 2025 at 08:40 AM, Maynard Wright, P. E., W6PAP wrote:
That would have been in 1958 when I bought the NC-183. Before that I had an
S-38E
Maynard, I bought a NC-183 to replace my S-38D in the early 1960s. I just loved that big receiver.
Brian
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Re: NANO VNA H4 , Implausible measurement results?
On Thu, Apr 3, 2025 at 08:40 AM, Maynard Wright, P. E., W6PAP wrote:
That would have been in 1958 when I bought the NC-183. Before that I had an
S-38E
Maynard, I bought a NC-183 to replace my S-38D in the early 1960s. I just loved that big receiver. Brian
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Re: NANO VNA H4 , Implausible measurement results?
Hi, Ed,
That's true! I remember hearing the phrase "you can work the world with watt and a wet noodle," but I didn't fully understand what was going on at the time.
I did cut an old broadcast receiver chassis in half, use the three tube sockets for a 6AG7, a plate coil, crystals, and leads to the hand key and it put out, I think, about a watt or two and I had fun powering it from my NC-183. I mounted a meter on the chassis for tuning. It's still in the attic somewhere. I used a circuit from the 1952 ARRL Handbook, using a parallel resonant circuit with one variable instead of ARRL's pi-network.
That would have been in 1958 when I bought the NC-183. Before that I had an S-38E and borrowing power from that would have been more difficult. I don't think that I would have been competent enough to build a power supply from scratch so the auxiliary socket on the NC-183 was pretty handy.
73,
Maynard
W6PAP
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On 3/31/25 09:57, AG6CX via groups.io wrote: Maynard and others:
You and we were most fortunate to be initiated with one of the most robust sunspot cycles of modern times in 1957!!
Same story at pre-Nano VNA KN1CJO in southern Maine. Worked all over the place, including all TV sets in the neighborhood.
Antenna was classic Windom, usual length, but fed with 300 feet of single wire to bannana plug into the DX-20 antenna port, me serving as T-R relay.
We are equally fortunate to still be able to remember all that, and be alive to write about
Ed McCann
AG6CX
Sausalito
On Mar 31, 2025, at 8:45?AM, Maynard Wright, P. E., W6PAP via groups.io <ma.wright@...> wrote:
?I got my Novice license in 1957 and used a single wire routed out the window and up to the brick chimney and then across the yard about 100 feet to a pole. It worked fine, with my best DX using a Knight Kit 50 watt (input) transmitter being an Argentine station in Antarctica. I worked a few Japanese stations and some South Americans from my QTH in Northern California, never realizing that my antenna was really awful.
When I upgraded from Novice to Conditional in 1958, I used a 100TH with the same antenna to work folks on AM and CW. With either transmitter, I had to stand up and throw a knife switch on the wall to go from receive to transmit.
I also still have a bunch of QSL cards from that era that bring back nice memories.
The important thing was that my Knight Kit with a pi-network and my 100TH with a swinging link coupler didn't care much about the SWR. I simply tuned for about a 10% drop in plate current and no red glow from the 100TH and everything worked fine. With a modern transmitter that wants something approximating 50 ohms, such an antenna would require a tuner and the losses in the tuner might use up a lot of the generated RF energy.
My most modern rigs here still use pi-networks, which is why I can get away with using a wire in the attic draped over air conditioning ducts and water pipes and work DX, not like a real DXer would want, but enough for a casual guy.
73,
Maynard
W6PAP
On 3/31/25 08:07, Jon via groups.io wrote:
Joe,
I got licensed a decade after you and did not have a chance to use a balun
or 50 ohms coax then. My 40 and 80m dipoles were fed by 75 ohms TV cable. I
did not have an SWR meter either. Still I could work a lot of DX including
a few W land stations with my homebrew 3 x 807 radio, 120W CW and straight
key. I still have a couple of W land QSL cards in my precious collection.
73
Jon, VU2JO
On Mon, Mar 31, 2025 at 7:50?PM Joe WB9SBD via groups.io <nss=
[email protected]> wrote:
Yup!
The Balun Craze is a new Generation thing. Got licensed in 1975, Never
ever heard of a Balun.
All my dipoles were direct feed.
Only till recently has the myth of a dipole without a balun will not work.
just like a 40 meter Dipole will not work on 15 meters!
tell that to all the Novices that got their license in the 70's.
Joe WB9SBD
On 3/31/2025 8:53 AM, Zack Widup via groups.io wrote:
I have never seen a problem feeding a dipole directly with an unbalanced
feedline. The last dipoles I had up (which were for 40 and 30 meters) were
just fed by connecting the two leads of the coax directly to the antenna
wires attached to an insulator at the center of the antenna. SWR in both
cases, when the antenna was trimmed, were around 1.05:1. And I worked 180
countries on 40 m CW with that antenna and Japan fairly often on 30 m CW.
Zack W9SZ
<
Virus-free.www.avg.com
<
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Mon, Mar 31, 2025 at 7:59?AM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:
Hello Hobride,
Unfortunately you have not supplied a photo of your test setup.
A dipole is balanced at the feedpoint, your VNA is unbalanced.
I suspect your problem is that you do not have a balun or choke at the
antenna feedpoint to prevent the feeder from affecting the measurement.
I won't make any guess as to why the VSWR appears lowest at 513MHz, but
I do suggest you use a balun or choke at the antenna.
HTH...Bob VK2ZRE
On 31/03/2025 11:25 pm, Milton Engle via groups.io wrote:
You did not indicate the range of your sweep.
Try setting the sweep range to 150MHz to 190MHz, recalibrate open/short/load, then measure.
I suspect that you will find the lowest VSWR near 171MHz, indicating that the element lengths are a bit long.
The third harmonic of 171 is 513
Milt
N3LTQ
On Mar 31, 2025, at 03:51, hobride via groups.io <hobride= [email protected]> wrote:
?Hello everyone,
I have bought a NANO VNA H4 to build simple dipole antennas.
Now I have made a simple dipole antenna for testing. This should be
tuned for 172 MHz. The total length is ~83 cm (2,72 feet), one leg is
~41.5
cm (1,36 feet).
When I now connect this antenna and try to measure it, the result is a
lowest SWR (1.15) at 513 MHz.
Can this be possible? I am not a radio specialist. I am an IT guy.
I have flashed the NANO VNA H4 to the latest firmware (tried DiSlord
and Hugen) and also calibrated it.
Perhaps I need to make further settings after flashing?
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On Thu, Apr 3, 2025 at 08:11 AM, alan victor wrote:
The R and L for above SRF of the C serves as a DC block
while adding a stabilizing R and an L for the match.
I had guessed the DC block above SRF might be useful even when C was not the LF value. Thanks for the insight on R and L, Alan. Brian
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Well.....here's another one for you: SM inductors. Most of the suppliers quote Q at 1 MHz. 1) The RF "resistance" (due to skin effect) should be used instead of the DC resistance. 2) Outside of RFI suppression, who really uses them at 1 MHz. Where are the plots of Q vs. frequency? Or RF "resistance" vs. frequency? This is why I always source MuRata who gets it right. CoilCraft? No. Dave - W?LEV On Wed, Apr 2, 2025 at 10:34?PM Brian Beezley via groups.io <k6sti= [email protected]> wrote: By coincidence, I just added an image showing capacitance and dissipation
factor plotted by my S-parameter plotter. It was derived from an .s2p file
provided by Kyocera. Scroll to the last image:
One thing I don't understand. Manufacturers specify useful frequencies
several times the capacitor self-resonant frequency, as revealed by the
.s2p files they supply. The 33 pF shown departs from 33 pF as it approaches
its 1.6 GHz SRF, which is nowhere near the 10 GHz specified upper frequency
limit. All the capacitor manufacturers seems to do this. Why?
Brian
-- *Dave - W?LEV* -- Dave - W?LEV
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On Wed, Apr 2, 2025 at 03:34 PM, Brian Beezley wrote:
One thing I don't understand. Manufacturers specify useful frequencies several
times the capacitor self-resonant frequency, as revealed by the .s2p files
they supply. The 33 pF shown departs from 33 pF as it approaches its 1.6 GHz
SRF, which is nowhere near the 10 GHz specified upper frequency limit. All the
capacitor manufacturers seems to do this. Why?
This is common practice in microwave power amplifiers and and some MMIC designs as one component brings in two. The R and L for above SRF of the C serves as a DC block while adding a stabilizing R and an L for the match. The same tactic is used with distributive L. First glance at some PA designs will most likely not make sense without recognizing that the parasitic is used to advantage. A complete sim is required adding in all device models including the passives.
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On Thu, Apr 3, 2025 at 06:21 AM, Jim Lux wrote:
You just design for the parasitic values.
That's what I finally guessed designers must do. Check out the Y21 method plot for capacitance I just posted for a different capacitor. Above the first two resonances, capacitance returns to a positive value, though not the LF or rated value. Brian
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On Wed, Apr 2, 2025 at 08:14 PM, Jim Lux wrote:
And they’ll measure for a very wide range.
After looking at more .s2p capacitor files, I've concluded that the file comments refer to the measurement frequency range, not the recommended frequency range for the part. I've attached S-parameters for an 82 pF porcelain capacitor that are pretty wild. Capacitance calculated with the S21 and Y21 series-through methods differ greatly. Brian
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To elaborate on this a bit. Let’s think about a standard 0602 sized part - that’s 0.06” long or about 1.5 mm. A piece of wire that long has an inductance of about 1.5 nH.
With, say, 33 pF, that’s resonant at 715 MHz. And yet, such parts are regularly used in all sorts of circuits at higher frequencies. You just design for the parasitic values.
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On Apr 2, 2025, at 20:14, Jim Lux via groups.io <jimlux@...> wrote:
?The max frequency is probably more about where losses get too big.
And they’ll measure for a very wide range. Most design tools can deal with staying away from the SRF, if supplied with the part parameters.
After all, at microwave frequencies most parts have a very complex and varying impedance.
On Apr 2, 2025, at 15:34, Brian Beezley <k6sti@...> wrote:
?By coincidence, I just added an image showing capacitance and dissipation factor plotted by my S-parameter plotter. It was derived from an .s2p file provided by Kyocera. Scroll to the last image:
One thing I don't understand. Manufacturers specify useful frequencies several times the capacitor self-resonant frequency, as revealed by the .s2p files they supply. The 33 pF shown departs from 33 pF as it approaches its 1.6 GHz SRF, which is nowhere near the 10 GHz specified upper frequency limit. All the capacitor manufacturers seems to do this. Why?
Brian
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k6whp
Donald S Brant Jr
