Per avere il valore zero sul diagramma di Smith (puntatore alla estrema sinistra) devi mettere il connettore SHORT. Il Mar 1 Apr 2025, 14:14 paolo.vecchi via groups.io <paolo.vecchi= [email protected]> ha scritto: I buyed a nanovna H 3.6. When I try to calibrate it, after the full
procedure, if I set a Smith diagram and I connect THRU the two ports using
the supplied cable the value is 50 ohm instead of 0. I resetted and
repeated the calibration a lot of time but with the same result. Can you
help me? Thanks
|
Port 2 is 50Ω as it should be, why do you imagine that it would be 0? On Tue, 1 Apr 2025 at 14:14, paolo.vecchi via groups.io <paolo.vecchi= [email protected]> wrote: I buyed a nanovna H 3.6. When I try to calibrate it, after the full
procedure, if I set a Smith diagram and I connect THRU the two ports using
the supplied cable the value is 50 ohm instead of 0. I resetted and
repeated the calibration a lot of time but with the same result. Can you
help me? Thanks
|
I buyed a nanovna H 3.6. When I try to calibrate it, after the full procedure, if I set a Smith diagram and I connect THRU the two ports using the supplied cable the value is 50 ohm instead of 0. I resetted and repeated the calibration a lot of time but with the same result. Can you help me? Thanks
|
Re: NANO VNA H4 , Implausible measurement results?
Hello Jon,
As you wish to use the antenna on the higher harmonics as well as 2M, I would suggest you use ferrites to create a Common Mode Choke (CMC) as noted by Roger.
I suspect (but do not know, I am no expert here) that it would be difficult to build a broadband balun to cover your frequency range (x5, x7) at TX power levels.
As for some of the other comments to this thread, I did not say that your antenna would not work without a balun or CMC.
What I said was that without a balun or CMC, the connection of an unbalanced VNA to a balanced dipole would not give correct measurement results of the antenna because the feedline would become part of the antenna measurement as also noted in other responses in this thread.
Your experience when you used a replacement "load" to do your calibration just emphasises how critical it is to do calibrations correctly and to treat your calibration SOLT "standards" with care and respect.
We can measure antennas till the cows come home and hypothesize on the results for twice as long, but we all know that the most unlikely collection of bits and bobs will form some sort of antenna that may, or may not, enable QSOs one way or the other. However a successful QSO is not scientific evidence of a "good" or "bad" antenna.
If it works, great. But do not use this as evidence of optimum antenna performance:-)
The "suck it and see" approach may not quite equate to measured results:-) Just my 2 cents worth.
Cheers...Bob VK2ZRE
toggle quoted message
Show quoted text
On 1/04/2025 12:25 am, Jon via groups.io wrote: Bob,
Would you suggest a voltage balun or current balun at antenna feedpoint?
One ham told me that if you use a voltage balun, it can bring down the high
noise I have on 80m.
Regarding the original question, I am tempted to think like Milt. I see a
lot of harmonic resonance in NanoVNA tracings when I set the range high on
purpose. In fact I use them to work higher bands. I am able to work North
America from VU on 12m, using my 80m center-fed dipole mounted at just 5m
height and 100W, with a little bit of touching up with the N7DDC tuner.
That would be the seventh harmonic resonance!
73
Jon, VU2JO
On Mon, Mar 31, 2025 at 6:29?PM 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?
|
Re: NANO VNA H4 , Implausible measurement results?
Yes,a dipole will work without a balun. But it is not a dipole anymore. The outer surface of your coax shield becomes part of the antenna system. This can give inaccurate results with the VNA. In real world usage it will distort the radiation pattern of the antenna and can provide a path for RFI in unexpected places. It's not rocket science but it *is* radio science.
toggle quoted message
Show quoted text
I have never seen a problem feeding a dipole directly with an unbalanced
feedline.
--
73
-Jim
NU0C
|
Your first link redirects to the same url the OP posted but I got to ask: What is your issue with the paper being hosted in Bosnia&Hertzegovina, the paper originated there. On Mon, 31 Mar 2025 at 20:44, Jim Lux via groups.io <jimlux= [email protected]> wrote: Other sources that are in other countries than Bosnia Hertzegovina
The authors have a number of other interesting "measure component with a
VNA"
Measuring impedances of DC-biased inductors by using vector network
analyzers
|
Re: NANO VNA H4 , Implausible measurement results?
I suspected the 50 Ohm calibration resistor and ordered two new ones.
After recalibration and measurement, the SWR is 1.26 at 172 MHz and 1.65 at 522 MHz.
Both measurements with SOL calibrated center frequencies 172 span 50 MHz and center 522 MHz span 50 MHz
that is much more plausible to me, i'm right?
I think that was the reason.
thanks for your support
|
Other sources that are in other countries than Bosnia Hertzegovina
The authors have a number of other interesting "measure component with a VNA"
Measuring impedances of DC-biased inductors by using vector network analyzers
|
Re: NANO VNA H4 , Implausible measurement results?
The SWR for a 50 Ohm cable will depend on the feedpoint impedance at the end of the cable. The impedance will depend on the antenna dimensions, its height, and its proximity to the environment. If the antenna is supported horizontally, its impedance at resonance could vary from a few Ohms to a maximum around 90 Ohms and then down to about 72 Ohms as the height is increased. If you are seeing a minimum SWR at your operating frequency, the length of the antenna is at or very close to a half-wave. Sometimes you can bend the ends of the antenna towards the ground and reduce their length to bring the impedance to 50 Ohms and an SWR of 1.0.
|
Re: NANO VNA H4 , Implausible measurement results?
You need to calibrate your coax SOL at the far end, so your readings look like your antenna is at the vna and not some distance away.9 On Mon, Mar 31, 2025, 12:58 AG6CX via groups.io <edwmccann= [email protected]> 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?
|
Re: NANO VNA H4 , Implausible measurement results?
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
toggle quoted message
Show quoted text
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?
|
Re: NANO VNA H4 , Implausible measurement results?
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
toggle quoted message
Show quoted text
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?
|
|
|
I ran into a research paper on measuring capacitors using a VNA that might be of interest. It analyzes capacitance and ESR accuracy for the S11 reflection, S21 series-through, and S21 shunt-through measurement methods. The paper covers connector parasitics and fixture deembedding. Lots of useful graphs.
Brian
|
Re: NANO VNA H4 , Implausible measurement results?
Have you turned on the VNA's Smith chart? At what frequencies thru your sweep does the trace cross the chart's center (no reactance) line? Those are your antenna's resonant frequencies. The one closest to the center is your best resonance...
|
Re: NANO VNA H4 , Implausible measurement results?
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?
|
Re: NANO VNA H4 , Implausible measurement results?
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
toggle quoted message
Show quoted text
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?
|
Re: NANO VNA H4 , Implausible measurement results?
It's measuring the 3rd harmonic which shows a nice low SWR. how far below 172 Mhz did you start your scan?
Joe WB9SBD
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On 3/31/2025 2:50 AM, hobride via groups.io 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?
|
Re: NANO VNA H4 , Implausible measurement results?
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?
|
Re: NANO VNA H4 , Implausible measurement results?
Bob, Would you suggest a voltage balun or current balun at antenna feedpoint? One ham told me that if you use a voltage balun, it can bring down the high noise I have on 80m. Regarding the original question, I am tempted to think like Milt. I see a lot of harmonic resonance in NanoVNA tracings when I set the range high on purpose. In fact I use them to work higher bands. I am able to work North America from VU on 12m, using my 80m center-fed dipole mounted at just 5m height and 100W, with a little bit of touching up with the N7DDC tuner. That would be the seventh harmonic resonance! 73 Jon, VU2JO On Mon, Mar 31, 2025 at 6:29?PM 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?
|
Jim Shorney
hobride
Ken