## Simple Meshtastic Radio

My take on a home made solution for an affordable, reliable radio:
(no superfluous parts - very low energy consumption)

open radio / inside a camera bag

- WisBlock Meshtastic Starter Kit: no display (not needed), no GPS (taken from phone), very low energy consumption
- cheap enclosure 100 x 60 x 25 mm for electronics (no screws)
- 3.7V 18650 rechargeable battery + battery holder
- toggle switch (no standby consumption)
- antenna (bendable 90°) either 868 MHz (Europe) or 915 MHz (USA) + pigtail (IPEX-SMA)

Make sure both antenna and pigtail match, so they must be both SMA, or alternatively both RP-SMA.

All parts above combined cost me around 50€.

I used a soldering iron, a hot glue gun, a step drill bit, double sided tape.

## Antennas

Important: never power on your radio without a mounted antenna, this can destroy your hardware (power is reflected back to the radio).

A good antenna is crucial for the radio to function properly.

A NanoVNA is very helpful to test if an antenna is resonant at the specified frequency (otherwise it's useless).
The Return Loss should be >= 10dB at the used frequency, which means that at least 90% of the power is going out of the antenna, and only 10% is reflected back to the radio.

     RL    back  out  VSWR
    ---------------------------
     0 dB  100%   0%  infinity
     1 dB   80%  20%  17
     2 dB   63%  37%   9
     3 dB   50%  50%   6
     5 dB   32%  68%   3.5
     6 dB   25%  75%   3
     8 dB   16%  84%   2.3
    10 dB   10%  90%   2
    15 dB    3%  97%   1.4
    20 dB    1%  99%   1.2

    RL ..... Return Loss
    back ... reflected back to radio
    out .... going out of antenna
    VSWR ... Voltage Standing Wave Ratio

You can find good NanoVNA clones for about 50€/$ (beware of really cheap/bad clones).

The screenshot shows a very good Return Loss of 22dB.

The antenna needs to be in vertical position while testing, so it's best practice to build a little stand for it, so one can test without touching the circuit, which would inevitably falsify the measurements.

It's highly recommended to only trust specialized shops (Mouser, Rokland, RAK store) for antennas, because there is simply too much mass produced garbage out there (talking from experience).

Here you can see the inside of one good example, and the worst offender so far:

Here an example of a classical (home made) ground plane antenna, using an SMA socket and 2 mm copper wire, after calculating the lengths here:

Can easily be trimmed by making the vertical wire a little too long, and cutting off one mm after another until it matches perfectly, while having it attached to a NanoVNA.

## Line of Sight

To easily find out if two places are within line of sight, you can use this
Path Profiler

line of sight

no line of sight

## Waterproof Solar Panel Radio

The RAK store has this nice enclosure where there is enough space for both a 18650 battery and a RAK 19003 Mini Board.

The above combination is not supported by the mounting kit, so this is just a personal hack, as you can see if you zoom in on the details.

## Simple Standalone Device

Support for Meshtastic is increasing continuously. These are CircuitMess Chatter 2.0 devices (they come in pairs). I found them on US amazon, also available on ebay.

They have some limitations: they only support MediumSlow instead of LongFast, and have a lousy antenna, but work great if those limitations are acceptable for one's use case.

If you're a hacker you can replace the radio chip with a cheap Heltec RA-62 to support LongFast, and mount a decent antenna.