Allstar micro-node

M0RVB

I finally got round to putting my Allstarlink node together after looking at it sitting almost completed for a week. Poor thing. Anyway, it's now functioning but I want to add the LEDs.

Software-wise it turned out a bit of a faff. I had already signed up and got a node number and set a password etc. My first attempt was via the Raspberry Pi image downloaded from the Allstar wiki. That seemed to go in just fine with a fairly easy setup and well scripted information on the wiki. All seemed ok except for when I wanted to install Allmon... the instructions for which began with the need to install git. That failed and so I did the usual update / upgrade cycle - which I really ought to have done right away as the image is quite old. After that, nothing worked. The USB interface was not working and so there was no radio functions. Power cycling did nothing.

So I installed the hamvoip image. One nice thing about the Pi and similar thing is you change SD cards and this changes the o/s and everything. Hamvoip went in fine with a fairly automatic installation and after a couple of loops where I'd missed something it now works fine. It comes with Allmon and Supermon installed. (the Allstar image does not have a web server and so the Allmon installation would have failed anyway even if I had not already given up).

Not picking on the Allstar image - had I taken more time I would have set up a Raspbian system and manually installed the Allmon software onto this, as detailed in their wiki. But, having got hamvoip working I will stick with that for now.

So... now to go off and figure out exactly why I built this thing anyway!!

Edit: Ok, I spoke too soon. Having connected to a test server the audio that comes back, allegedly the same as what I sent, is awful with a tone and buzzing in the background which the audio only just makes it over. Something is wrong... audio from the box is fine with the generated voice announcements perfectly clear, as well as a few calls heard when connected to hubnet receive-only. The HT is fine as I can hear good quality audio via a scanner. Hmmm...

Edit 2: I've experimented with every parameter and made no difference. I have increased the mic gain on the HT as it seemed low even with a high setting in the simpleusb setup. But the noise remains. It seems that whenever I transmit anywhere near the node it happens, and simply moving to the other side of the shack cures it to a great extent. Currently the radio is connected to a dummy load but swapping for a small antenna makes no difference. Moving the dummy load well away from the node with an extension coax makes no difference to the noise if transmitting near the node. So the transmission is clearly getting in somewhere that it should not. I have verified the HT is ok by monitoring on a scanner, so no issue there.

Edit 3: Adding a ferrite around the cables between the radio and the CM108 has helped a little in that I can get closer to the node and not get this noise played back in parrot mode. Unfortunately I have put all my small clip-on ferrites in A Safe Place, ever to be seen again, so I can't add more right now.

I have carried out a tactical withdrawal i.e. the node is sitting under the desk in disgrace. No amount of ferrite'ing, re-routing wires or even running the node from a lab supply makes any difference to this noise. The only thing I can be reasonably sure of is it is some interaction between RF from the HT and the audio chain, so the CM108 I guess. Holding the HT next to the node while monitoring it on a scanner shows no audio issues but playback in parrot mode and it is there every time. Moving away from the node cures it to a great extent but no amount of shielding works. I could (should!) investigate further but I have other projects to take care of plus a bunch of DIY stuff.

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Allstar Link project

One of my ongoing projects was to build an Allstar Link node. I had acquired a working Baofeng 888 from eBay some time ago and a few days ago duly programmed it (all the channels in case I ever accidentally turn that switch) to the 70cm frequency I want to use. Also in the box of waiting bits was a Pi 3B, ex my Portsdown project (that has a Pi 4 now), a CM108 USB dongle and a dummy load. Anyway, it came to the top of the project list (= I wanted something relatively simple to fiddle with. The CM108 came from Amazon and only cost a couple of quid. They had four available, all of which are now here! Following the excellent guide (among other similarly excellent guides) at https://allstarsetup.com/modify-a-cm108-sound-fob/ this was abused into something ready for use. Next came the 888 modifications (all relevant information can be found via https://allstarsetup.com/allstar-mini-node-construction-details/) which went fine except the information I was reading did not make clear how one powers the radio. I figured that out. Note that the radio needs 3-and-a-bit volts so two diodes in series with the 5V line works ok here (I need to add another yet).

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