Mobile Allstar node

AllStar is a network of analog repeaters or nodes linked through the internet. It is based on a modified version of Asterisk, an open-source PBX software. Like for the telephone, numbers are assigned to users/node. This allows them to ‘dial-up’ other nodes and create temporary or permanent ‘conferences’. In simple terms, you can interconnect two radios at different locations via the internet.

Since Asterisk comes from the telephone world, it is really easy to configure, auto-patch or reverse auto-patch. You just need to get a SIP number and voila, you can use your radio to make a phone call.

Asterisk is also modular. There are modules to connect your Asterisk node to Echolink or IRLP.

AllStar Node plugged to a 7Ah battery
AllStar Node plugged to a 7Ah battery

Allstar Node Numbers

The first thing to do before you start building your Allstar node is to get a node number. If you also want your node to be Echolink capable, you need to request an Echolink node number. Create an account on the allstarlink website. Once your account is created you will be able to request your node numbers.

Allstar node

To build my Allstar node I used the following parts.

Optional (depending on how you build your node)

  • PVC electrical box
  • Some screws
  • Connectors and wires
  • Power source

To build my Allstar node, I used a Raspberry Pi 3B+, because I had one lying around in my shack. Any Raspberry Pi should work, even a Pi Zero. If you build a mobile node and your concern is energy consumption, the Pi Zero is probably your best option. With some of the Raspberry Pis, you might also get a WiFi dongle if you want to connect wirelessly.

The most important piece of an Allstar node is the sound card. Two signals are needed for the software to work properly. These signals are the COS1 and PTT. The COS will tell the Allstar software that the radio is receiving a signal (squelch is open). The PTT will switch the radio into transmit mode when something needs to be sent over the air. If you run a quick search on the internet you will find people modifying cheap USB sound cards dongles. Some of these modifications are really good and some are not. The PCB card on these fobs are really tiny and I didn't feel up to the task of soldering onto these microscopic pads. This is why I got my sound card from the Repeater Builders website. I am using the RIM-Lite sound card. You can also use the excellent card from DMK Engineering. This card is a bit more expensive, has more features, and has probably the best audio quality.

Inside the AllStar node
Inside the AllStar node

Since I have 12 Volt PowerPole strips everywhere I power my box with 12 Volts. It also makes it easier to plug the node into a 12-volt cigarette lighter plug on any car. To step down the voltage to 5 Volt for the Pi and 3.7 Volt for the radio I use 2 buck converters. I could have used only one and a resistor or a simple voltage regulator to drop down the voltage to 3.7 Volt for the radio, but buck converters are more stable and using one more buck converter made my life easier.

The radio I used for the node is a Baofeng BF-888. This is a low power radio, which is perfect for a mobile or home node. The radio is capable of putting out 3 Watts on high power, but I programmed the radio to transmit with only 1 Watt. With that set up I can reach my node for 2 to 3 miles around my house, which is plenty enough for my use.

BF-888 modifications

The BF-888 is one of the best radios for building an Allstar local or mobile node. You can find one for less than $20 on Amazon. The price can go as low as $8 if you buy them in quantity. It is also easy to disassemble and to modify. This radio doesn't have a keypad nor a display and needs to be programmed. You can use Chirp for programming it.

Depending on the version of the radio you get, the PCB might look slightly different from the pictures here. But the differences are small enough that you should be able to easily find where to solder the leads.

BF-888 Mods (COS)
BF-888 Mods (COS)
BF-888 Mods
BF-888 Mods (TX/RX/PTT/Power)

You need to connect the TX, RX, COS, PTT, and Ground to the sound card. The RX audio wire is connected to the volume potentiometer right before the audio amplifier. This will provide a cleaner audio signal.

Depending on the sound card you chose to work with, you will need to solder all the leads to a DB9 or DB25 connector. Refer to the documentation of your sound card for these connections. The voltage from the audio needs to be lowered in order to avoid distortion. I use a 47 kΩ resistor on the TX and RX. These values are not critical. The Allstar software will allow you to set the input and output level. I also use a 10KΩ resistor for the COS.

I have also removed the LED next to the antenna and the microphone. The LED is not needed and the microphone picks up background noise if the box is installed in a noisy place.

Software

Once you have connected everything you can download a Linux image from HamVoip for the Raspberry Pi. On this image, Asterisk is already installed and pre-configured. Follow the instructions on their website on how to boot the image and configure Asterisk. You will need your node number and the AllStarLink password to configure Asterisk.

To build a node or a repeater using another computer than a Raspberry Pi, I would use the ALS2 image, it also works perfectly fine, but can work on virtually any computer. It will require a little more work to install and configure it. For example, I am using ALS on a virtual node hosted in the cloud.

Admin menu screenshot
Allstar administration menu

You will also need to find a free frequency for your node. The Baofeng BF-888 is a UHF radio. You need to find a frequency in the 70 cm band. To program the BF-888 you can use the free software Chirp. It is available for Linux, MacOS, or Windows.

Once your node is running, you can connect to my Allstar node 40490 for a QSO with me or my friend N6YUV. To connect press PTT and dial *340490 on your keypad. To disconnect just press the PTT and dial *140490.

Useful commands

*1 node numberDisconnect Link
*3 node numberConnect link in transceiver mode
*70Local connection status
*71Disconnect all links (macro)
*80Force System ID
*81Say System Time

Example of connections to the node 40490:

Node 40490 connections

Future improvements

Heavy populated networks like the WinSystem (2560) or HUBNet (41522) in the UK can make your radio run with a high duty cycle. Even when you use your radio with the lowest power setting it can generate a fair amount of heat when it is enclosed in a box. This is why I installed a small Fan on my node. Right now, the Fan runs all the time. My next project to improve this mobile node is to have the fan temperature controlled.


  1. Carrier Operated Switch 

  2. AllStar link 


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