Re: NanoVNA


Chris Swisher
 

Tim (and CMRA members),

The following is the observations and opinions of one quasi-literate and easily distracted ham radio operator:
1. Amazon is your friend, read the peoples' comments who take the time to rate their experiences;
2. The NanoVNA was a collaborative project with a really smart dude with a great idea. A cheap, easily manufactured piece of test equipment that can be improved upon without spending a fortune. The Chinese have taken low cost manufacturing to an art, often at the cost of component (and shielding) removal. There are several versions out there, Mine came with a battery and without shielding. I can take the time to add a diode for battery monitoring and shielding to improve RF isolation, it wasn't in my unit.
3. Don't expect the results that a $60k commercial Vector Network Analyzer will give, be realistic in the returns, and figure out ways to improve your interpretation of the results.
4.The firmware that shipped with my unit was hopelessly behind the curve on the capabilities that are currency offered. The small screen size and my lack of Superman vision led me to tie it into my laptop. To make that connection I had to learn to update firmware using Dfuse software (you'll learn about it later) across a USB in Windows 10. Each of these parts have many facets that could "brick" your new $50 investment.
5. Join the groups.io NanoVNA-users. Like drinking from a firehose, the secret is to slowly acclimate yourself to the environment then jump in. The knowledge base there is incredible, both technically and operationally. (Does the hardware allow this new measurement to be performed?)
6. Check out my 160 meter antenna sweep. It is a 65 foot grounded Rohn 25 with a three element Moseley TA-33M. Gamma shunt fed at 56 feet, the tri-bander acts as a capacitance hat. I had only a VSWR meter and a grid dip oscillator to find the resonant frequency of the tower. I guessed well, it appears.
NanoVNA160MVERT.jpg
Notice as well that VSWR(lower right) is a poor substitute for return loss(upper right), which is a much more accurate indication of antenna efficiency. I have worked 42 states and 8 countries on 160 using this antenna, and winter is around the corner!
Here is a phased pair of Cushcraft 11 element two meter yagis.
NanoVNA2Mdual11elbeams.jpg

Two things to note: I may have had a aberrant measurement while I moved a feedline. The sweep took about 5 minutes. Ignore that and imagine a smoothed line. There are two different resonant frequencies of this system. It could be that I wasn't exact with the electrical lengths of my homebrew phasing harness, or the antennas may not be tune to the same point of resonance. Either way, increasing usable bandwidth across two meters is a good thing at my QTH.

I'm still learning how to use the other capabilities of the unit, including time domain reflectometry. Being able to spot cable faults, and reasonably measure length will save me time in the long run. If you want to expand your vocabulary in RF, which is a good thing, this is a good investment. When you figure out that you need lab grade measurements, this will be a fond memory.
I can put on a presentation that will leave CMRA glassy eyed and asleep if necessary. Alternatively, I might expose myself as a fraud on the RF expert level.

On Thu, Oct 24, 2019 at 9:16 AM <tims173@...> wrote:
Chris,

Who did you buy your NanoVNA from.  I have looked on eBay and noticed there is quite a variety of combinations of pieces and parts from different sellers.

After testing it, do you still recommend it?

Thanks.

73

Tim E. Spurgeon
W0TES

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