开云体育

On Thu, Aug 10, 2023 at 09:51 AM, Keith Ostertag wrote:

1) What exactly is the |S21| plot? I don't know what the vertical axis
represents and its units. Is it the LogMag but with different units?

The |S21| transmission coefficient indicates the insertion loss or gain of your amplifier on a linear scale. It gives you the transmission ratio (output magnitude/input magnitude) in the forward direction. A number smaller than 1 is loss and greater than 1 is gain. S21 Log mag is is a logarithmic dB scale equal to 20 *Log10 |S21|. For example Marker 3 in your plot has a value of |S21| = .575 and 20*log10(0.575) = -4.8 dB which is what is shown as S21 Gain.

Roger

Thank you Dave and Stan. So would the |S21| linear graph vertical axis have units? Or is it unit-less? (if that is the correct term)

I think in you saver graph that the |s21| plot is just the linear
representation of the magnitude of the reflection coefficient (max value
1). The top graph, called logmag s21, is a logarithmic representation of
the same data represented in dB, and is what we normally use for most
purposes.

No attachment. I'll try attaching the grahic.

Dave - W?LEV

On Thu, Aug 10, 2023 at 5:58?PM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Here is a graphical - no math - representation of what the S-Parmeters
indicate. It is usually assumed to be in a 50 +/- j0 ohm system.

[image: image.png]
S11: With the output (right side) properly terminated, S11 indicates how
well the input (left side) is matched to a 50 +/- j0 load. As a scalar
measurement, this would be the input SWR.

S12: With the input (left side) properly terminated, S12 represents the
reverse isolation when probed from the output side (right side).

S21: With the input as the energy source and the output probed, S21
represents the forward transfer characteristics of the network. This may
be either gain in the case of an active circuit or a loss in the case of a
passive attenuator, for example.

S22: With the input properly terminated, S22 represents how well the
output is matched to a 50 +/- ohm load. As a scalar measurement, this
would be the SWR of the output port.

Any of these parameters can be expressed in either vector form or
logarithmic form, as in logmag (of the reflection coefficient of the input
or output port).

Dave - W?LEV

On Thu, Aug 10, 2023 at 4:51?PM Keith Ostertag <n3kxz@...> wrote:

Here is a link to a nanovna-saver plot of my current IF filter:


The bandwidth is a bit narrow. How does the ripple look?

A few basic questions:

1) What exactly is the |S21| plot? I don't know what the vertical axis
represents and its units. Is it the LogMag but with different units?

2) When I run the "Analysis" it says "Insufficient data for analysis.
Increase segment count." But increasing the segment count does not clear
that statement. Perhaps I am misunderstanding what it wants?

Here's a link to the analysis:


Thanks,
Keith
N3KXZ

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

Here is a graphical - no math - representation of what the S-Parmeters
indicate. It is usually assumed to be in a 50 +/- j0 ohm system.

[image: image.png]
S11: With the output (right side) properly terminated, S11 indicates how
well the input (left side) is matched to a 50 +/- j0 load. As a scalar
measurement, this would be the input SWR.

S12: With the input (left side) properly terminated, S12 represents the
reverse isolation when probed from the output side (right side).

S21: With the input as the energy source and the output probed, S21
represents the forward transfer characteristics of the network. This may
be either gain in the case of an active circuit or a loss in the case of a
passive attenuator, for example.

S22: With the input properly terminated, S22 represents how well the
output is matched to a 50 +/- ohm load. As a scalar measurement, this
would be the SWR of the output port.

Any of these parameters can be expressed in either vector form or
logarithmic form, as in logmag (of the reflection coefficient of the input
or output port).

Dave - W?LEV

--
Dave - W?LEV

Here is a link to a nanovna-saver plot of my current IF filter:

The bandwidth is a bit narrow. How does the ripple look?

A few basic questions:

1) What exactly is the |S21| plot? I don't know what the vertical axis represents and its units. Is it the LogMag but with different units?

2) When I run the "Analysis" it says "Insufficient data for analysis. Increase segment count." But increasing the segment count does not clear that statement. Perhaps I am misunderstanding what it wants?

Here's a link to the analysis:

Thanks,
Keith
N3KXZ

The minimums are almost the same. . . thanks for the measurement.

Vy 73, Roger DL2YDP

Second time lucky ...

--
Mike G8GYW

Here's an EFHW I measured at the antenna and in the shack.

First I calibrated the NanoVNA at the far end of the feeder (18 metres long and about 0.5dB loss) and measured the VSWR there. Then I calibrated again on a short cable and measured inside the shack.

Here's the result.



--
Mike G8GYW

On Tue, Aug 8, 2023 at 08:06 AM, WY6K Mike Watts wrote:

Even though I have rebooted several times NanoVNA-Saver will not start. The
DOS window opens but then it does nothing. It seems to me that v6.2 broke
something that v5.3 needs to run. Maybe python? I don't know what to do to
get it going again....

You have a corrupted NanoVNA-Saver ini file which contains all the settings parameters. You have to do a file search for this file ----> NanoVNASaver.ini and then delete it. Then try running Saver again and it should now work for you.

Roger

Under windows?

Do you use the exe file?

For the exe, you don't need python installed.

Did you wait a very long time? Like 4 or 5 minutes after the dos window
appears? Sometimes it takes a very long time for python to get everything
started up after a change.

On Tue, Aug 8, 2023, 8:06 AM WY6K Mike Watts via groups.io <wy6k=
[email protected]> wrote:

Even though I have rebooted several times NanoVNA-Saver will not start.
The DOS window opens but then it does nothing. It seems to me that v6.2
broke something that v5.3 needs to run. Maybe python? I don't know what
to do to get it going again....

I would think you would want to know exactly where the antenna stood before
complicating matters by assuming the antenna is ok and your not knowing
where your hi swr readings are coming from.

Fred
N4CLA

On Mon, Aug 7, 2023 at 10:58?AM John Baines via groups.io <jbaines=
[email protected]> wrote:

Peter,

It depends what you want.

Measuring at the antenna allows you to check the resonant frequency and
the complex impedance of the antenna (to design a match to the coax
impedance - often 50 ohms)

Measuring at the indoor end of the coax lets you see the complex impedance
of the antenna plus coax system to determine whether a tuning unit is
needed.

73

John
M0JBA

On 7 Aug 2023, at 15:47, Peter N0PGM <pgmelton@...> wrote:

Hello,

Once my antenna is up it will have a 50ft run of coax that enters my

home. Do I measure the swr at the base of the antenna (before the 50ft of
coax) or inside the house (at the end of the coax)?

Thanks in advacne,

Peter

Even though I have rebooted several times NanoVNA-Saver will not start. The DOS window opens but then it does nothing. It seems to me that v6.2 broke something that v5.3 needs to run. Maybe python? I don't know what to do to get it going again....

Cable loss to antenna will reduce the forward, then return reflected power.

It can be calibrated out but the round trip loss reduces the dynamic range of network analyzer by the round trip dB loss. If you are looking to get impedance at the antenna you must calibrate out the cable because you also need the phase information correct for network analyzer to figure terminal impedance at end of cable.

Also on NanoVNA, when measuring antennas you have to be careful of strong nearby radio transmitters, like AM or FM broadcast stations. The input mixer chip of NanoVNA can be overloaded by strong RF signals.

Francesco, I purchased mine from a vendor on E-Bay in China. My F-V2 had just died and was thinking about buying a replacement. I had already seen reviews of this model and decided to give it a go. I was shocked that I received mine in about 10 days. It arrived in near perfect condition.

The firmware is pretty good but not 100% stable. I'm seeing some strange issues with reading when doing tight calibrations. For example, if I calibrate from 700-1100 meg and run a simple SWR sweep then the device gets into a weird state. I have to reset the calibration and load a known-working save file.

The functionality is really nice. The large screen is amazing and makes it really fun to use. It is very hefty however. If you want something that's pocketable then this definitely is NOT the device for you. It's large and heavy.

There are some UI issues that I don't like but they are workarounds for them. You can easily touch-drag markers anywhere on the screen if they get in the way, etc.

I hope the firmware becomes more stable in the short term. I'm debating about buying another F-V2 in the mean time for something pocketable. The firmware on the V2 was near perfect, at least for my needs.


-Nick, k7cj

NOPE!? ? Due to coax losses, the analyzer doesn't see the reflected power.
SWR is LOWER with a long coax.
Assuming the coax is not damaged of course.

/The SWR at the transmitter will be higher at the antenna than at the receiver.///
Shouldn't the SWR be lower, because at the transmitter, power reflected from the antenna will be attenuated by losses in the transmission line?

On Mon, Aug 7, 2023 at 07:47 AM, Peter N0PGM wrote:

Once my antenna is up it will have a 50ft run of coax that enters my home. Do
I measure the swr at the base of the antenna (before the 50ft of coax) or
inside the house (at the end of the coax)?

The SWR at the transmitter will be higher at the antenna than at the receiver. The more attenuation in the transmission line the greater the difference. See attached graph below.

Roger

Coaxial cables have loss.
With long cables it is best to match the antenna to 50 ohms before
connecting it to the cable. If this is not done, a mismatch between the
cable impedance and the antenna reflects some power back to the
transmitter. The cable loss dissipates some of the reflected power and less
of it is reaches the transmitter than was actually pushed back by the
antenna.

If the cable is mismatched at both the antenna and transmitter ends, then
part of the power reflected by the antenna travels back and forth between
mismatches creating further losses in the cable.

Power lost in the cable does not get radiated and does not show up as bad
VSWR at the transmitter end giving the false impression of a better match
than is actually present.

__Joe VE6JSL

On Mon, Aug 7, 2023 at 09:06 Zack Widup <w9sz.zack@...> wrote:

I generally measure it at the end of the coax in the shack. That way I see
what the rig is going to see. I have had really long stretches of coax to
the antenna and the NanoVNA was unable to measure the SWR. I think it
required more power to overcome cable losses. In that case I had to check
it with a lot shorter length of coax.

73, Zack W9SZ

On Mon, Aug 7, 2023 at 9:47?AM Peter N0PGM <pgmelton@...> wrote:

Hello,

Once my antenna is up it will have a 50ft run of coax that enters my

home.

Do I measure the swr at the base of the antenna (before the 50ft of coax)
or inside the house (at the end of the coax)?

Thanks in advacne,

Peter

--

__Joe Leizerowicz
6424 34 Avenue NW, Calgary, AB T3B 1N1
403-604-7791