Build a Hotspot

This guide will walk you through the building of the jumbospot ham radio hotspot for DMR, System Fusion, D-Star, P25, NXDN, etc. The companion guide on configuring them will get you up and running at least on DMR, but the other options are easy to turn on and configure once you get these basics down.

First, let’s go over hardware selection. A common mistake among amateur radio enthusiasts is to simply go on eBay and purchase a jumbospot board from a seller located in the US and build their hotspot with that. If you do that, you will end up with an inferior board that will not work as well and most likely won’t last as long as if you bought it from China. The reason for this is that Chinese manufacturers often unload their old/inferior stock by shipping to an employee based in the US so he can sell it from here. You will end up with a 1.2 or 1.3 board when, at the time of this article, the 1.7 board is the current model. If you have a friend complaining that his board only works on UHF and won’t work on VHF, check the board for a version number. You either won’t see one at all or will see a 1.3 there. This is why…

Second, let’s look at the LCD screen. They’re most likely listed as 0.96” I2C IIC Serial 128X64 OLED LCD Display Module for Arduino or some variation of that. With these, you CAN get one from a US seller. There is only one thing you have to make sure of: you have to make sure that the pins are correct. From left to right on the pins you should see VCC, GND, SCL, SDA. It’s very common to see these modules with the VCC and GND pins switched in location. These will burn up as soon as your hotspot is powered on. You have to get the pin order right. In addition, you will see some with more than 4 pins. Don’t get these. You want a 4 pin screen with VCC, GND, SCL and SDA in that order. You can’t rely on pictures. Oftentimes, the Chinese sellers will include stock pictures that look similar to their boards, but aren’t their exact boards.

Can you get one with the screen soldered on from China? It’s VERY hard to find a 1.7 board with the screen soldered on. When you do find them, they’re usually significantly more. I hope I haven’t scared you off at this point because I’m about to make hardware selection very easy for you. I’m going to give you links from vendors I’ve had great success with. I’ve assembled over 150 boards and the vendors I’m about to link to have never done me wrong:

Jumbospot board by elecdesign2015

If you can’t get one from him for some reason, here is a backup: Jumbospot board by 2012moon816

LCD screen by diy-electronic

Now, you’ll notice that jumbospot comes with an internal antenna as well as a socket and external antenna. If you’re going to use the internal antenna, do not solder the socket on. If you’re going to use the external antenna, remove that white strip at the bottom. That is the internal antenna. If you have both antennas on the board, you will have decreased performance and possibly shorten the lifespan of your unit.

There is one more board to buy: a raspberry pi zero W. If you’re close to a Fry’s, you can probably pick one up for $10 or so. Notice the W though. That stands for wireless and you need the wireless functionality for this to work. Don’t just stick a Raspberry Pi zero in it…get the W. However, you can also get the model with the headers presoldered onto the board. This is the version I usually got and it cuts down drastically on the amount of soldering you have to do. Raspberry Pi Zero WH at pishop.us

The last thing you need to buy is a case. A lot of people like this C4labs case. It comes with two tops: one for the internal antenna and one for the external antenna. They give you both tops and you can build with one and then decide on the other later or whatever you wish.

The actual building of the hotspot is pretty simple if you bought the Zero WH. You have to solder the LCD screen on and that is it. I recommend you use a 3d printer to print out the 3d printed jumbospot lcd guide I designed. It will hold the lcd screen straight and flat so you can solder the 4 pins. There are pictures there to show you how to use the guide and solder that screen on. It’s the outer row of pins and they’re to the far right if you’re looking at the bottom of the board. They’re right up against the connector poking up on the right side. They’re labeled on the front 3.3, GND, SCL, SDA.

That’s all there is to it. If you bought the C4labs case it will show you how to put your boards in and build your case around them. Essentially, the connectors on the jumbospot just slide down onto the pins on the Raspberry Pi Zero W. Please check out my configuration guide that will walk you through getting this thing up and running.