Nano VNA
I recently bought a Vector Network Analyser. These
instruments used to cost hundreds of pounds, but the Nano VNA V2 sells for
around £60.
What does it do? It is used to characterize the impedance of
antennas, cables, connectors etc. It can measure SWR, Impedance, insertion loss,
return loss and much more. Its range is 50 kHz to 3 GHz, but the measurement
range is programmable so, for example, you can just scan the width of an
amateur radio band. It also has a time-domain reflectometry function allowing
length of coax cables and identifying faulty connectors in a cable run.
The unit I bought has a 7cm screen. This is small and
the screen is a bit hard to read but it does make the unit very portable - it fits in my pocket. A larger size model is available. The screen
is touch sensitive and a stylus is provided which makes using the menus easier.
If you find the screen too small, PC software is available but of course this
limits portability – one of the major advantages of the NanoVNA.
NanoVNA and Accessories
Accessories:
- · Stylus
- · Two SMA-SMA Cables
- · SMA Socket-Socket.
- · 50 ohm calibration load
- · Short circuit calibration load
- · Open circuit calibration load
- · Carrying case (but the zip on mine soon broke)
Be careful not to lose these accessories! It has a built-in
rechargeable battery that is charged via the USB socket. The connectors are SMA - these are not PL-259s and need to be treated with care.
Using the NanoVNA is straightforward, but do read the online
instructions. When it is switched on four traces appear. I usually switch three
of these off to simplify the display. The frequency range over which you want
to measure is then selected and the next job is to do a calibration for the
frequency range. This takes a couple of minutes by connecting the Open Circuit
first, then the Short Circuit and finally the Dummy Load. There are five
memories that can store frequency range/calibration. If you want to change the
frequency range, and you have not previously stored it, then you need to do another
calibration and store that.
I found the NanoVNA easy to use. For years, I have used SWR
meters to check the performance of my antennas etc. but these only tell part of
the story and manually plotting SWR curves is tedious. With the NanoVNA you can
see the selected frequency range on the screen and quickly switch to other
functions, such as real and imaginary impedance. If you want to use the more
advanced functions then read the many online tutorials, such as The Antenna Theory Website
(antenna-theory.com). If not connected to a PC then the quickest way to
record results is to take a photo of the screen. I found time-domain reflectometry
function a little tricky but everything else is straightforward.
4m Whip
Antenna VSWR
