开云体育

If you have a close-by strong source of RF energy like FM or AM
broadcasters, police, ambulance, CB'ers, hams, ....... any of those and
more could be affecting the readings. This is not all that uncommon in
cities when the VNA is connected to a large antenna.

Dave - W?LEV

On Tue, Apr 1, 2025 at 7:51?PM kellogs via groups.io <mihai0226=
[email protected]> wrote:

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun
and one at the VNA S11 port. No body / coax inadvertent movements,
everything taped down near the antenna.

Thanks

--

*Dave - W?LEV*


--
Dave - W?LEV

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in 11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun and one at the VNA S11 port. No body / coax inadvertent movements, everything taped down near the antenna.

Thanks

No, but a guy may have already worked DXCC while you're still arguing about
whether an antenna is good or not. Get on and use it. Play with it later as
needed.

Zack W9SZ

<>
Virus-free.www.avg.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Tue, Apr 1, 2025 at 10:34?AM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

QUOTE: 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:-)


**

I'd also add that a low SWR is also not an appropriate means of declaring
an antenna good.

Dave - W?LEV

On Tue, Apr 1, 2025 at 6:59?AM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:

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


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?

--

*Dave - W?LEV*


--
Dave - W?LEV

Yes. Alan is one of the "big boys" and belongs to Tek. Those by amateurs
and others may be highly questionable. At least those are my experiences
with YouToob. For example, addressing ferrites, Fair-Rite has a
wonderfully useful and solid site, even some directly aimed at the amateur
radio community. So do Agilent, Tek, Keysite, Advantest, R&S, HP, and
many.....many others. To properly utilize YouToob presentations, one must
first know at least the basics of the knowledge they are seeking. Without
a basic knowledge, you are highly likely to be "snake oiled" and
"witchcrafted" and "sorceried" and.......

Dave - W?LEV

On Tue, Apr 1, 2025 at 4:03?PM Donald S Brant Jr via groups.io <dsbrantjr=
[email protected]> wrote:

On Tue, Apr 1, 2025 at 11:36 AM, W0LEV wrote:

Beware of most YouToob presentations.

You can absolutely trust Alan Wolke W2AEW's videos. He is a Tektronix
Field Engineer, I know him personally and knows his stuff 100%.

And, to your original question you must be looking at S11 Smith Chart
display to see 50Ohms; S21 magnitude should be 0dB when the thru is
connected.
Best regards, Don Brant

--

*Dave - W?LEV*


--
Dave - W?LEV

Even a linear wire, not coiled, has some measurable inductance. At zero
length the display on the Smith chart, will show a single value of zero at
the extreme left of the real axis. That point on the Smith Chart is
0.00.... ± j 0 ohms. That represents a short circuit. As the measurement
point along the linear wire is increased, both the RF resistance (skin
effect) and inductance increase. Therefore, the measurement will depart
upward on the chart (inductive reactance) and to the right along the
central line on the chart. Since the vast majority of RF measurements are
assumed in a 50-ohm system (the industry standard except for the television
people), the chart is laid out around that value. ONLY the central point
(see the previous attachment) represents 50 ± j0 ohms.

The extreme right position along the central axis (real only) represents an
open circuit or theoretically infinite resistance.

An excellent tool both for analysis, modeling, and learning the Smith Chart
is SimSmith. It's free and available at the following URL:



That URL also contains many good tutorials addressing the Smith Chart.

More information can be had at the following:



Dave - W?LEV



On Tue, Apr 1, 2025 at 3:52?PM Jon via groups.io <vu2jo0@...>
wrote:

Dave,

One doubt about the Smith Chart: Why does the so-called resistive component
change as you move across the tracing? If it was the true electrical
resistance due to the ohmic resistance of the wire and feedline, it should
not change.

Forgive my ignorance. I have started using NanoVNA only recently.

73
VU2JO

On Tue, Apr 1, 2025 at 9:15?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Possibly the attachment will help.

Dave - W?LEV

On Tue, Apr 1, 2025 at 3:36?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Beware of most YouToob presentations. Those by the "big boys" which

offer

their instruments for lots of $$$$ are good and solid. Many of those

by

amateurs or "self proclaimed experts" are flawed. Take anything on

YouToob

with a huge grain of salt!!

Dave - W?LEV

On Tue, Apr 1, 2025 at 1:59?PM Zack Widup via groups.io <w9sz.zack=
[email protected]> wrote:

If the video on Youtube notes that the impedance should be zero, it

is

incorrect. The THRU impedance should be 50 ohms. I just checked on

three

NanoVNA's, and they all measure 50 ohms.

Zack W9SZ

On Tue, Apr 1, 2025 at 8:48?AM Paolo via groups.io <paolo.vecchi=
[email protected]> wrote:

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo (
)
youtu.be ( )

( )
Inviato da iPhone

Il giorno 1 apr 2025, alle ore 15:39, Dragan Milivojevic via

groups.io

<d.milivojevic@...> ha scritto:

? 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

<

Virus-free.www.avg.com
<

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

On Tue, Apr 1, 2025 at 11:36 AM, W0LEV wrote:

Beware of most YouToob presentations.

You can absolutely trust Alan Wolke W2AEW's videos. He is a Tektronix Field Engineer, I know him personally and knows his stuff 100%.

And, to your original question you must be looking at S11 Smith Chart display to see 50Ohms; S21 magnitude should be 0dB when the thru is connected.
Best regards, Don Brant

Dave,

One doubt about the Smith Chart: Why does the so-called resistive component
change as you move across the tracing? If it was the true electrical
resistance due to the ohmic resistance of the wire and feedline, it should
not change.

Forgive my ignorance. I have started using NanoVNA only recently.

73
VU2JO

On Tue, Apr 1, 2025 at 9:15?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Possibly the attachment will help.

Dave - W?LEV

On Tue, Apr 1, 2025 at 3:36?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Beware of most YouToob presentations. Those by the "big boys" which

offer

their instruments for lots of $$$$ are good and solid. Many of those by
amateurs or "self proclaimed experts" are flawed. Take anything on

YouToob

with a huge grain of salt!!

Dave - W?LEV

On Tue, Apr 1, 2025 at 1:59?PM Zack Widup via groups.io <w9sz.zack=
[email protected]> wrote:

If the video on Youtube notes that the impedance should be zero, it is
incorrect. The THRU impedance should be 50 ohms. I just checked on

three

NanoVNA's, and they all measure 50 ohms.

Zack W9SZ

On Tue, Apr 1, 2025 at 8:48?AM Paolo via groups.io <paolo.vecchi=
[email protected]> wrote:

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo (
)
youtu.be ( )

( )
Inviato da iPhone

Il giorno 1 apr 2025, alle ore 15:39, Dragan Milivojevic via

groups.io

<d.milivojevic@...> ha scritto:

? 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

<

Virus-free.www.avg.com
<

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

That being said, the aim of a radio amateur is to have a QSO, without
damaging equipment and causing interference (RFI)!
All these - balun, common mode choke, SWR meter and NanoVNA, are aids to
achieve that end result.

73
Jon, VU2JO

On Tue, Apr 1, 2025 at 9:04?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

QUOTE: 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:-)


**

I'd also add that a low SWR is also not an appropriate means of declaring
an antenna good.

Dave - W?LEV

On Tue, Apr 1, 2025 at 6:59?AM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:

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


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?

--

*Dave - W?LEV*


--
Dave - W?LEV

Possibly the attachment will help.

Dave - W?LEV

On Tue, Apr 1, 2025 at 3:36?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Beware of most YouToob presentations. Those by the "big boys" which offer
their instruments for lots of $$$$ are good and solid. Many of those by
amateurs or "self proclaimed experts" are flawed. Take anything on YouToob
with a huge grain of salt!!

Dave - W?LEV

On Tue, Apr 1, 2025 at 1:59?PM Zack Widup via groups.io <w9sz.zack=
[email protected]> wrote:

If the video on Youtube notes that the impedance should be zero, it is
incorrect. The THRU impedance should be 50 ohms. I just checked on three
NanoVNA's, and they all measure 50 ohms.

Zack W9SZ

On Tue, Apr 1, 2025 at 8:48?AM Paolo via groups.io <paolo.vecchi=
[email protected]> wrote:

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo (
)
youtu.be ( )

( )
Inviato da iPhone

Il giorno 1 apr 2025, alle ore 15:39, Dragan Milivojevic via

groups.io

<d.milivojevic@...> ha scritto:

? 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

<

Virus-free.www.avg.com
<

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

Beware of most YouToob presentations. Those by the "big boys" which offer
their instruments for lots of $$$$ are good and solid. Many of those by
amateurs or "self proclaimed experts" are flawed. Take anything on YouToob
with a huge grain of salt!!

Dave - W?LEV

On Tue, Apr 1, 2025 at 1:59?PM Zack Widup via groups.io <w9sz.zack=
[email protected]> wrote:

If the video on Youtube notes that the impedance should be zero, it is
incorrect. The THRU impedance should be 50 ohms. I just checked on three
NanoVNA's, and they all measure 50 ohms.

Zack W9SZ

On Tue, Apr 1, 2025 at 8:48?AM Paolo via groups.io <paolo.vecchi=
[email protected]> wrote:

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo (
)
youtu.be ( )

( )
Inviato da iPhone

Il giorno 1 apr 2025, alle ore 15:39, Dragan Milivojevic via groups.io
<d.milivojevic@...> ha scritto:

? 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

<

Virus-free.www.avg.com
<

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

--

*Dave - W?LEV*


--
Dave - W?LEV

QUOTE: 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:-)

**

I'd also add that a low SWR is also not an appropriate means of declaring
an antenna good.

Dave - W?LEV

On Tue, Apr 1, 2025 at 6:59?AM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:

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


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?

--

*Dave - W?LEV*


--
Dave - W?LEV

All info here is accurate. BUT, to save time, calculate the "electrical"
wavelength needed mathematically for the "rough" estimate. Wavelength =
300/frequency (MHz) multiplied by the specified Velocity Factor from the
manufacturer. Then, add several inches for "tuning" via the VNA.

Michael L Robinson, KC0TA

“In the beginning of a change the Patriot is a scarce man, and brave, and
hated and scorned. When his cause succeeds, the timid join him, for then it
costs nothing to be a Patriot.” ― Mark Twain

When Tyranny becomes Law, Revolution becomes Duty!






On Sun, Mar 30, 2025 at 2:44?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi
a Calibrated smith diagram can show you easily the serial resonance
frequency and the parallele one ( Xr = 0 Omh ) ,
- use the 401 sweep points option to have maximum frequency accuracy .
- Stimulus band should be selected to be the minimum needed .
- Calibration and measurement prefered after at least 10 minutes for
thermal stability .

you can use open coax terminaison or short one , they should give
approximatly the same results .

73's Nizar.

On Mon, Mar 31, 2025 at 03:20 PM, Joe WB9SBD wrote:

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.

When I started in ham radio, 46 years ago, indeed almost nobody used baluns with dipole antennas. Nowadays instead it's very common to use them, and there are at least two good reasons for this change!

One reason is interference between radio equipment and other stuff in the home. Computers, switching power supplies, TVs, even refrigerators and lamps. When no balun is used, the feedline is part of the antenna, so the antenna extends into the shack and the home's electrical wiring, severely worsening the interference situation. With a balun that's working ideally, the feedline does not radiate, and does not receive signals, so is not part of the antenna. That moves the actual antenna out of the home, away from the switching power supplies and other stuff, reducing the interference both ways. Back before the 1980s this wasn't such a big factor, because there were no switching power supplies, no computers, no LED lamps, no CFL lamps with electronic ballasts, no LAN, and so on. TVI was the only point of concern, and sometimes handled by establishing time schedules for ham operation and for TV viewing. But today it's an important factor, because there are so many interference-causing and interference-sensitive things that it's not acceptable to turn them all off by a schedule.

The other reason is how hams assess the condition and usability of their antennas. In the "good old times", the test was whether the transmitter could be loaded up into that antenna, without arcing, and how many contacts it produced. The antenna would be cut by trial and error to such a length that it worked well enough with that one specific feedline, in its fixed position. At most a ham might measure the SWR, but many didn't even have an SWR meter. Today instead, with instruments like the nanoVNA, hams have become scientists, trying to understand exactly what's going on, and will discover things like the antenna being resonant outside the band and operating on one the sides of the resonance dip, or that moving around the coax cable will change the SWR, or that adding even a little piece of coax will drastically change the impedance, shifting the resonant frequency. So they prefer to use baluns, to reduce the sensitivity of the antenna's parameters to feedline conditions, in order to be able to at least begin to understand what's happening with their antennas, and to achieve a setup that works more like theory tells.

I began using baluns in 1989, when I got into packet radio, and needed to run a computer at the same time as a radio, and interconnect the two, hopefully without causing feedback loops.

About that 172MHz dipole, I would expect it to measure differently according to its position relative to the nanoVNA and other stuff, to be sensitive to feedline length, etc. The usual stuff. If a balun is added, I would suggest a current balun, since we don't know how the antenna will be oriented, what will be close to it, but we do know that we want the lowest possible common-mode current on the feedline.

Thanks a lot

Inviato da iPad

If the video on Youtube notes that the impedance should be zero, it is
incorrect. The THRU impedance should be 50 ohms. I just checked on three
NanoVNA's, and they all measure 50 ohms.

Zack W9SZ

On Tue, Apr 1, 2025 at 8:48?AM Paolo via groups.io <paolo.vecchi=
[email protected]> wrote:

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo (
)
youtu.be ( )

( )
Inviato da iPhone

Il giorno 1 apr 2025, alle ore 15:39, Dragan Milivojevic via groups.io
<d.milivojevic@...> ha scritto:

? 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

<>
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Grazie
Inviato da iPhone

Hi, I have seen a video on Youtube…

NANOVNA analizzatore di antenne: come usarlo ( )
youtu.be ( )

( )
Inviato da iPhone

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