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Re: NanoVNA vs. MFJ-259B Antenna Analyzer

Bob Albert #17330 While I appreciate and respect all the opinions here, I feel the need to reply. I have owned MFJ-259 and nanoVNA and can say without question that the nano is far superior in every way that is important to me.? This may not be true for other users, but I cannot lavish enough praise on the nano.? It can be set up for the very casual ham and it's capable of sophisticated and accurate measurements for the advanced engineer. I use my nano nearly every day.? I have had problems with one of my antennas and the nano nails it every time.? I can plot an SWR curve over almost any frequency range and see the best frequency.? As I adjust the antenna I can see the effects instantly over the entire band.? I can see where it has low SWR even far from design frequency.? I can see resonance, whether it be at SWR minimum or not.? And bandwidth is instantly presented to me. The Smith chart lets me measure line length and characteristic impedance.? It can be a TDR as well.? As a bonus I can measure capacitors, resistors, and inductors for frequency sensitivity, ESR, self resonance, the whole schmear. At first it seemed like a cheap toy but I quickly learned better.? If anyone has trouble figuring it out I stand ready to help.? Mostly it practically operates itself.? Sure it has limitations but a careful user can work around them easily. 73, Bob K6DDX toggle quoted message Show quoted text On Wednesday, September 9, 2020, 06:13:20 PM PDT, 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 à 20:53, Jim Lux <jimlux@...> a écrit : 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.

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