I have two 259 variants and will probably keep both of them. They are a good tool for the primary job intended, and are arguably a better solution for non-technical hams who don't want to be bothered with the learning curve. Each device has it's place.
73
-Jim
NU0C
On Wed, 9 Sep 2020 21:13:03 -0400
"Pierre Martel" <petem001@...> wrote:
The NanoVNA and the MFJ AA are directed to 2 different groups of people.
The MFJ is more of an entry level testing device that take care of checking
an antenna in a fast and simple way, like using a SWR meter but more
conveniently, no big radio to drag with you and less power used so you can
tune all over the rf spectrum without causing interference to other
services.
The NanoVNA is more of an advanced device that is also convenient in many
ways, but has a sharper learning curve and has more advanced features that
an average ham will ever need.
Of course the price of the device will put a pressure on MFJ to design a
lower price AA. But also not everyone will accept to buy a device that does
not have a over the counter support and can be abandoned by the designer.
That needs to be taken in consideration also. And the guys at MFJ do know
the market to whom they sell to. They are losing a very small part of the
market to the NanoVNA cause many hams did want a small device to test
antenna, filters and such and do not have the money to buy more
advanced devices.
Pierre
VE2PF
Le mer. 9 sept. 2020 ¨¤ 20:53, Jim Lux <jimlux@...> a ¨¦crit :
On 9/9/20 5:13 PM, David Eckhardt wrote:
Well, Jim, I'm a total nerd when it comes to RF and the HP 8753C. And,
yes, I've tuned / adjusted antennas using only the Smith Chart. Those
were
antennas aimed at UHF and the Hi line at 1420 MHz for radio astronomy.
Seeing whether and how much L or C needs to be added or subtracted is
invaluable. Bringing the intended frequency into the center is quite
useful! Once that is done, then, yes, I look at bandwidth using SWR (in
a
50-ohm system). I use the Smith Chart quite a bit in 'tuning' various
antennas.
Yes, tuning in the "design a matching network" sense - which is why I
think it's more a design tool - you look at the smith chart, figure out
what components/networks will make it work.
That's different from a interactive "field instrument" where you're
turning a knob (or adjusting element lengths, or cutting wire off a
dipole).
Dave - W?LEV
On Wed, Sep 9, 2020 at 11:32 PM Jim Lux <jimlux@...> wrote:
On 9/9/20 2:52 PM, n9xcr@... wrote:
I would have to say the NanoVNA is probably putting a hurt on MFJ's
sales of analyzers.
It really addresses a totally different need. The MFJ is a handy device
- Having a meter needle/LCD display to see the "dip" at resonance is a
pretty fast way to trim a dipole.
(with all it's idiosyncracies, but then, so does the NanoVNA have
idiosyncracies).
Nobody trims a dipole using a smith chart <grin>
Smith charts are really more of a design tool, especially if you're
designing/adjusting a matching network. You measure the device you want
to match (or you get supplied with the chart by the mfr) and then you
can piecemeal together a LC matching network by drawing lines on the
chart.
I'd hate to tune a multisection filter or a multistub tuner with a smith
chart - that mag S11, mag S21 vs frequency is what you want for that.
One of the more interesting applications I see for the NanoVNA going
forward is to support making a backyard/living room antenna range for
microwave antennas.
The other thing it would be great for is measuring the self and mutual Z
in an array antenna like a 4 square. Right now, everyone sort of runs a
model and assumes that it's like the model. Or you use the 1/4 wave
"current forcing" scheme, which has some limitations.
The NanoVNA would also be invaluable for doing something like a 3
element beam with identical length elements, bringing all 3 elements to
the ground with coax, and then putting Ls and Cs to "tune" the beam.
Just like a SteppIR, except without the moving parts in the air.
Jim Shorney