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NanoVNA - the £47 handheld 900 MHz VNA

Why do you need a VNA? Simply put they're a far better way of checking antenna tuning than using an SWR meter or a regular antenna tester and can generally be used to test filters and other components. Two or more plots can be displayed simultaneously, with Smith chart and SWR being a useful combination for antenna testing.

The club has a little Sark 110 VNA handheld, which has an LCD screen that lets you see exactly what your antennas are up to. These are great little devices, covering up to 230 MHZ but they cost £330, so not an impulse buy.

Enter the NanoVNA, a handheld VNA with a 2.8" touchscreen and a frequency range allegedly extending up to 900 MHz. It appears to be possible to use it as a CW signal generator too (although it almost certainly generates square waves). You can also connect it to a PC by USB and a simple programme lets you control it and see plots on the PC screen. NanoVNAs generally come with a basic SMA calibration set consisting of an open circuit, a short circuit, a 50 ohm load, a pair of cables and an F-F back to back adapter. These are essential as the VNA only produces sensible readings if calibrated for the frequencies under test. The calibration process is quick and easy. The NanoVNA feature set probably isn't as wide as a more expensive VNA but at this price you are already getting more than you can reasonably expect.

NanoVNA kit


The design started off as an open source project on Github but a number of Chinese manufacturers have started making them and selling via Ebay and other online marketplaces. There are variations between these clones and it is difficult to know which one you will receive when you order as they may ship a different version to that shown in the ad. The better versions have screening round the input and output circuitry. Some people buying via Chinese sites like Alibaba find the device ships without a battery due to postal restrictions. There are also several different versions of firmware - some make it a 4-trace 2-port VNA. Others a 2-trace 1-port antenna analyser with a clearer display.

Although the NanoVNA is usable out of the box it is all a bit DIY - it doesn't come with a case or with a manual. You can find a basic 'Chinglish' manual online as well as a useful forum, stl files for 3D cases and firmware. The firmware is basic but does the job. Some people find there are glitches at 300 and 600 MHz so some firmware variants go to 800MHz max to avoid this.

I bought a NanoVNA from 'UK' seller sqcase. It looks slightly different to what was advertised, isn't the best version and the firmware is for a single port antenna analyser but it came quickly with a battery and no customs charges. It seems to work remarkably well for what is essentially a giveaway price. Unfortunately the SMA short circuit was missing from my calibration set and the seller unresponsive. Easy enough to make a shorted SMA as long as you have a spare plug - shame Maplin stores all closed!

Here's what mine looks like, displaying the Smith chart and SWR plot for a 2m/70cm handheld antenna. Note the rather fetching red case, printed with my Anycubic Mega 3D printer from a design on Thingiverse by VK5ZBR. I had to increase the size of the case fractionally and do a little filing as it was designed for a different clone but it is a snug fit and doesn't need any glue or fixings:

NanoVNA display



NanoVNA top



I'm still playing around with my NanoVNA and I'm not yet clear it works properly all the way up to 900 MHz. It seems to produce plausible results to 450 MHz. I made a temporary short circuit SMA using a PL259 and an SO239-SMA adapter which works ok at lower frequencies but isn't good higher up. I calibrated the VNA to 450 MHz using an SMA short of Colin G8RLZ's but the lack of a proper one here at home means it can't be recalibrated at the moment. Sorted soon hopefully!

You can buy a NanoVNA by searching Ebay and there's a helpful user group here: https://groups.io/g/nanovna-users.

73

Mike
G4RAA

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