Radioless AllStar node hardware build

This is just a blog of how I made the AllStar node into a desktop radio with a pleasing look. The actual software build of the Node isn’t covered here since the date the radioless node was built, new versions of AllStar node software have been released. Freddie Mac the Ham Radio Crusader has many excellent tutorials on how to get up a node up and running. https://www.youtube.com/@HamRadioCrusader

www.youtube.com/@electechyt The Video and the finished radio.

The story of why I wanted to build it like this. I have seen many tempting videos and web articles by some very experienced constructors and thought I could do similar with my own variation. I have already built 2 AllStar nodes with radios for myself and a good radio amateur friend. The last build was modified after the 5v buck converter became noisy and my audio suffered the inevitable squeal noise in the background. This is my own fault for choosing a cheap buck converter and poor wiring and separation practices. I was learning and because of the day job, I don’t get much time to spend developing.

This was AllStar node number 1, which I reconfigured and gave to a radio amateur friend.

The insides were not pretty. You can see the buck converter at the top, too close to the USB Audio dongle.

AllStar node number 2 which I modified a while ago by removing the internal Boafeng donor radio and replacing it with an externally-mounted mobile radio which also serves as a general VHF/UHF dual band set or Packet radio just be swapping the microphone and speaker connections.

The modified AllStar node with radio.

This is a little neater. I used 2 buck converters one to drive the radio with 7 volts and the other for the Raspberry Pi at 5 volts. No background squeals on this one.

This is the circuit board of the replacement radio. I changed the 3.5mm audio TRS jack socket for a TRRS type which had the buffered Carrier On Squelch (COS) signal on the extra wire. The fun was probing to find a convenient source of logic signal when a carrier meets the CTCSS tone and opens the squelch.

I commenced the layout on a spare piece of plastic which was the left-over lid from a DIY project at my Son’s house to hide an unsightly and unremovable, old, unused room heating thermostat. The plastic box hid it and blended in with the wallpaper. I kept the lid thinking, “I’ll need that one day”. I originally wanted a front-facing speaker but couldn’t find a pleasing looking case with the desired dimensions to fit the display, control knobs and switches and a speaker across the front so I cut a round hole in the plastic base and positioned over the ventilation grilles in the base of the case. It works… but works better after fitting some 10mm rubber feet to the case.

The next part was to load and configure the AllStar node software and test the kiosk software on the donor mobile phone. The phone is connected by WiFi to the same shack Access Point and automatically connects to the AllStar node on first boot.

Excuse the mess of glue. The phone was stripped, the home button wiring has two wires soldered across it and these are brought out to a switch on the front panel. Its an android phone that combined the power and home button. The case of the phone had to be reduced in width to fit in the radioless node case. Once the phone had been configured, I removed the microphone and speaker, there was no need for a SIM card or MicroSD card either. The battery is fixed with Duck tape now rather than the plastic tape in the picture above. This was just for the initial concept and testing. The phone was a new old-stock HTC and came in a sealed box.

The modified phone completed and tested ready for installation.

The modified front panel ready to accept the phone. I was using bits of tape and hot melt glue to hold it together whilst I tried out the fitting of the phone in the case. It was a very tight fit requiring removing some of the case inner moulding.

Commencing the wiring stage. The Veroboard on top of the Raspberry Pi was supposed to have logic components on it for switching and LED drivers but ended up being used as a way of connecting wires to each other.

I had purchased number of these CM108 USB Audio boards and modified them for use in other projects. The COS function isn’t needed on the Radioless node build, only the PTT line which is connected to the CM108 GPIO bus.

During testing, I found the transmit audio from the off-the-shelf cheap CB radio microphone was low. I modified this inexpensive microphone amplifier board which had manually selectable gain. But it was either too much or not enough. I added alternative resistors to get a compromise of around 15dB gain which works a treat. You can change the transmit audio level from within the AllStar setup but I prefer to get the audio level right in hardware first then this can be adjusted in software later.

The audio amplifier is a stereo 3 watt PAM8403 but I only needed one channel. The unused channel has it’s unused input grounded as a precaution. It gives plenty of volume in the shack even when in competition with other radios. The Microphone I purchased was a 4 pin variety so I used a matching socket with locking ring.

My Pi Hat with the switching and LED drive. This isn’t my design, I borrowed it from this design below.

Credit to G6OJB saving me the time of doing my own design. This one works very well and I throughly recommend the BAT43 diode to protect the GPIO from any potential voltage getting into the GPIO and destroying the CM108 chip. The design above used the newer CM119 which is similar to the CM108 which was in short supply.

The finished radio taking pride of place under the Multi-MMDVM hotspot in my shack. Yes you read that right, multi-MMDVM hotspot. This will be another blog post and when I get home and rebuild it (the case has become damaged).

This was when I was trying to fit MMDVM number 4 in an already messy, untidy case. It has DMR, C4FM/Fusion, D-Star and now POCSAG MMDVMs installed. Its a bit of a gimmick really since I wanted to have 4 modes all on independently at the same time. I was going to use an Arduino microcontroller plus some detecting and switching to manually or automatically select the MMDVM information to display on the 3.5″ Nextion touch screen. This project generated a lot of heat so I had to install a slim fan I recovered from a scrap laptop to help with ventilation. It worked surprisingly well. 3 Hotspots were on UHF 70cm band and the other on VHF. Even on the minimum power output of milliwatts, one MMDVM would de-sense the others and struggle to “hear” my radio on low power if I was more than 5 metres from the desk.

Family picture with the Radioless AllStar node battery charging in portrait mode on its side.

Radioless AllStar node hardware build

ByDave

By Dave

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