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Personal AllStar "Pocket Node" Based on the Baofeng 888


So, I was on a 20 year hiatus from amateur radio when a business associate, T.J. - KC8LTS, introduced me to P25NX dragging me back into the hobby after all these years. A short time later another associate, Dan - W2PUT, introduced me to AllStar and the rest is history. I hope that this entry will inspire others to make their own Allstar node and join the fun...

For those of you not familiar with AllStar, you can get an overview here Allstarlink and here Hamvoip.

After several mobile radio based nodes and a few repeater interfaces, I decided it was time to build an ultra portable node. The Boafeng 888 makes a great radio on the cheap and is well documented for Allstar service, so it was the obvious choice for my "personal node" One can get up and running with a Raspberry PI, SD card, 888, usb sound FOB, and a small assortment of cheap components.

My first 888 node was fairly typical. Radio > FOB > PI with no "integration" which worked very well.  Only issue was heat and a tendency to get some RF into the audio chain with a duck antenna. Using an external antenna and judicious placement (or a dummy load) was the cure. I could have left it like that, but I wanted something a bit more power frugal and compact.


I noticed there was quite a bit of space in the bottom of the 888 case so why not cram the FOB in there, right? My next version, shown on the right, sported this mod.
Well lets not stop there, look how tiny the RF deck is. Would both fit in a Raspberry PI case? Oh my, like it was made for it!

Which brings us to my current version, and the reason for this blog entry. Let's have a look...

First we need to pull the center USB tower from the PI3, which can be challenging, and run four component leads up from the board. Component leads were selected instead of wire to add support, which works very well.

Next we pull the SYBA FOB from its case, remove the USB plug and audio jacks (optional) The COS diode and PTT resistor are tacked on and brought up around the sides. I find notching the edge of the board where they wrap around helps, just be carful not to notch too far. This is IMO, the hardest part of the build. Be carful and enlist a friend with a steady hand and magnification if you do not possess either and watch the iron here, it's easy to pull a trace on this little guy.
I got the "mechanical" inspiration here: VKLink but prefer this "electrical" design: Hamvoip

The FOB then drops into the space created by removing the tower. Flow a little solder from the to rear pads to the remaining towers and solder in the usb leads and it is secured and ready to go...


Next, we have to pull the 888 out of it's case. I remove the mic, speaker, antenna jack, side button circuit board, flashlight LED, etc. On my most recent build, I also pulled the volume control and channel selector as I find, while useful in some cases, I really don't need them and the I can get everything into a standard sized case.


Bridging the 2 center connections on the selector pads gives you Ch 9 operation. You also need to bridge the on/off pads shown here:

Seeing as this is a personal node, designed to be in the vicinity of my phone (and my arse) I pull the final and simply bridge across the pads. This results in about 30mW of RF out. Things stay comfortably cool, and there is zero RF even with an internal helical antenna. The entire node pulls about 450-500mA. You can run an external SMA connector, and what ever antenna you desire, if additional range is required.


Pull this guy and solder a small jumper across the outer tabs.

For power, I just pull 5v off of the GPIO connector through a 1A diode which gets it right where the 888 likes it. Here is a schematic of what I am doing from Hamvoip.

RX audio is the green wire to the high side volume control
PTT is the orange wire to the PTT pad
TX audio is the white wire to the mic input
COR will be picked off of the audio IC on the top side of the board
All typical and well documented stuff...


2 component leads off the outer bottom ground connections on the deck are soldered to the USB and Ethernet towers. An additional lead from the deck to the micro USB jack secure it in front.


You can also see the helical antenna, wrapped in heat shrink, running parallel to the GPIO connector on the RF deck. Tap into GPIO pin 4 for power, make your audio connections to the FOB and your done. Follow the instructions found at hamvoip.org to get your new node up and running.



Here is a cheesy little video showing the whole mess in an off the shelf Ada-fruit case in operation. Apparently Doug wasn't around at the time I made this video :)



Please comment below if I can elaborate on any part of this. I'd love to hear about your build and any alterations you incorporate into your design. Thanks for reading, 73 Sean

Comments

  1. Nice Work. Good Job! Great Write Up! Thanks.

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  2. I can be reached on the FBIARC hub - 43732 Stop by and have a chat, I'd be glad to answer any questions...

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    Replies
    1. Hey Sean, Great write up!
      I have replicated your build and I’ve it’s to say I’m thrilled with it.
      I also had too much noise in the audio and it sometimes would false trigger COS . So annoying...
      I wrapped my own helical antenna as well and I’m getting decent range throughout my house and property.
      I couldn’t stand lugging around all the bits to make up the station, this all in one solution is the best.
      Thanks again. W2JON

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    2. Excellent! Happy to hear folks are giving it a go. Any pics?

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  3. I, I, I... wow I write like a 5th grader.
    You get the idea tough..

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    Replies
    1. Don't sweat it. I have to proof read and change my stuff multiple times to avoid similar faux pas. Didn't even notice...

      Delete

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