Quote: " There are far more people who think they know what SWR is
than there are people who can make sense of a Smith chart."
Spend some time learning about complex impedances and the Smith Chart. You
will never be sorry if you intend to remain a licensed amateur radio
operator and understand what you are doing.
Most hams don't even understand what SWR means. Most believe it indicates
resonance of an antenna. It may or may not. An antenna is at resonance
when the radiation resistance is purely resistive with no complex portion
to that resistance. This is the definition of resonance: +jX = -jX.
Amateur SWR meters are incapable of making a complex measurement of
impedance. Amateur SWR meters measure in a 50-ohm resistive-only system.
Therefore, any indicated SWR represents the scalar value of SWR in a 50-ohm
system with no complex measurement capability and indicates little
regarding resonance. Therefore, they can not necessarily measure resonance
of our antennas. If they were designed to measure in a 75-ohm resistive
system, they would measure a 1.5:1 SWR when embedded in a 50-ohm system.
Our SWR meters measure a 1:1 SWR when a purely 50-ohm resistive load is
attached to their outputs because they are designed to properly read in a
purely 50-ohm resistive system. They can't indicate resonance by adhering
to the definition of resonance. Nothing about resonance is indicated.
Therefore, they are, for the most part, incapable of indicating resonance
of an antenna. A VNA is fully capable of making complex impedance
measurements and can, therefore, indicate resonance of our antennas (and
other circuits).
Standard amateur grade SWR meters are incapable of indicating resonance of
an antenna structure due to their incapability of measuring the complex
portion of the presented impedance.
Dave - W?LEV
On Fri, Sep 11, 2020 at 10:58 PM Bob Albert via groups.io <bob91343=
[email protected]> wrote:
Apart from all the great things one can do with a nano, the main thing it
does for me is instruct. I mess with the external hardware, the frequency,
the display, and the most useful result is teach me how this radio
frequency stuff works.
I have learned a ton about transmission lines, lead length of components,
and so much more just from fooling around with the parameters.
Bob K6DDX
On Friday, September 11, 2020, 03:37:37 PM PDT, Jerry Gaffke via
groups.io <jgaffke@...> wrote:
David said:
If that's what others
want, go buy an antenna analyzer, but don't claim it's a VNA. It
certainly
is NOT!
The nanovna could be both, and be cheaper than most SWR meters.
The curious could get an education for their $50 if they play with it some.
If I were building nanovna's, I'd look hard at shipping it with a dumb
power up screen.
Show three GUI buttons: StartFreq, StopFreq, Advanced
And default to showing a graph of SWR.
Those wanting to use it as a VNA should be able to figure out they must
press the "Advanced" GUI button. Or maybe download other firmware.
Would likely sell ten times as many units.
There are far more people who think they know what SWR is
than there are people who can make sense of a Smith chart.
Jerry, KE7ER
On Fri, Sep 11, 2020 at 01:50 PM, David Eckhardt wrote:
Personally, I appreciate the NANO's 'acting like' my HP 8753C and other
far
more expensive VNA's. I understand the capabilities and know how to use a
true VNA. I have no use for an 'antenna analyzer'. If that's what others
want, go buy an antenna analyzer, but don't claim it's a VNA. It
certainly
is NOT!
The MFJ-227 which is marketed as a graphic VNA / antenna analyzer is NOT
a
VNA with only one port. Sure, it will measure S11 or Z11 (I presume in
complex form??), but how do I measure filter response or throughput of
any
circuit? Yes, a scalar analyzer can make that measurement in a scalar
manner but does not measure the complex response. In addition, for $380.,
the '227 does not cover the frequency range of the NANO's. Even the
MFJ-223 is not a true VNA and covers to only 60 MHz for $339. Prices
checked at MFJ as I write this email.
There is a place in the market for both an antenna analyzer and VNA. Why
should an antenna analyzer which is a rather numbed down VNA cost 3 to 4X
that of a REAL VNA which is FAR more capable? I don't get
it.......marketing........
Even if I had a need for an antenna analyzer, I would not pay approaching
$400 for a numbed down VNA when I can buy a very capable VNA for just in
excess of $100 which covers to 3 GHz, .....and WITH cal standards
included. I am more than happy with the NANO offerings from China. Keep
it up, guys!!!!
Dave - W?LEV
toggle quoted message Show quoted text ( #quoted-172116735 )
On Fri, Sep 11, 2020 at 7:06 PM Larry Rothman < @ve3lri (
/profile/ve3lri ) >
wrote:
The nanovna at this point in time, is essentially a small,
software-controlled analyser capable of KHz to GHz measurements.
There are now interface apps for Windows, Mac, Linux and Android which
all
command the NanoVNA to take specific measurements and to display the
returned data as graphical output in classic VNA formats.
But - it's the SOFTWARE that was written to specifically output the
data
in that VNA format ..... and the software can be changed to take
alternate
measurements and output data in ANY format the end user would like to
see
it in.
Of course, now you'll hear from the sticklers 'not to change anything'
and
'how lame it would be to dumb-down the output' which is absolute
nonsense!
There can be as many end-user variations of firmware for this device as
there is seen a need for - and for those self-indulgent, critical
individuals who don't like change - tough.
My $0.05 ('cause Canada doesn't have pennies anymore)
...Larry
On Friday, September 11, 2020, 10:20:28 a.m. EDT, Jerry Gaffke via
groups.io <jgaffke@...> wrote:
Perhaps we need a version of nanovna firmware with a simpler GUI.
Powers up showing a graph of SWR, and an easy way to set the start and
stop frequency.
Text at the bottom shows complex impedance at the start frequency,
and/or resistance+capacitance/inductance.
An "Advanced" menu button to get down into the rest of the
functionality.
Can still work with nanovna-saver.
Jerry, KE7ER
On Fri, Sep 11, 2020 at 03:44 AM, David Wilcox wrote:
This is a good argument if you are well versed in antenna analysis and
really
understand the capabilities of the MJF 259 family, nanoVNA, and
others.
I have
owned and used the MFJ and nano but when I am in the field and
sometimes
at
home I still fall back on my YouKits FG-01, a not cheap SWR meter (at
least in
my thinking) but it shows a nice understandable graph of my SWR and
impedance
as I adjust an antenna or antenna matcher). The manual is so simple
and
it
doesn¡¯t mention calibration, just plug and play. For what it is it
easily
does the job to tune my antennas and antenna matching devices to MY
SATISFACTION, but probably not accurate enough for the experts here.
The
simple wire antennas and verticals I use seem to work well to my
satisfaction
and I seldom need the Elecraft internal antenna ¡°tuners¡±. My good old
269
worked the same out of the box (without recalibration) but was big
and a
battery eater. If a ham wants cheap just use an old eBay noise bridge
(like
before we ever had these fantastic tools) or a coil and a GDO. You
will
be
close enough for ¡°government¡± work. This hobby is still fun for me
after
60 years and I make contacts with 100 watts or less, usually 10 watts
or
even
less. Too many Rolaids are consumed getting the perfect match and that
extra
one or two watts. That probably means a lot to those who collect wall
paper
and need the latest DX to brag about with your friends, but I think
there are
a lot of us out there who just want to communicate with our rigs, home
built
or factory built.
I have a flame suit on and don¡¯t really care. This is a hobby and I
read
the
super technical stuff just for fun even though I don¡¯t understand a
lot
of
it. Still learning.
K8WPE still learning at 75, licensed in 1960. Still having fun. And
¾±³Ù¡¯²õ
cheaper than a psychiatrist and less trouble than a mistress........
and
my
wife of 47 years always knows where I am.
David J. Wilcox K8WPE¡¯s iPad
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
*Dave - W?LEV*
*Just Let Darwin Work*
