In my previous post, I discussed the possibility of building a personal AllStar node instead of a community-wide one. This would not only be easier to make but would also be less time-constraining and could more than likely be done in a day.
The Conception
Back when I was first thinking about building an AllStar node, it never really crossed my mind to construct a node radioless. Because I wanted it to be community-wide, a radio-enabled node was a must. However, due to the complex nature of constructing a node with PTT and COS capabilities on the CM108 soundcard, this node would require skills way beyond my abilities.
Enter the radioless node - only one CM108 connection for PTT on pin 48, the VOL DN pin. Or, if you really want to make things easier, certain headset models with up/down/play/etc controls are just plug-and-play operation!
Radioless nodes require only a few things - a USB soundcard, a mic preamp board, an audio amplifier, and a microphone with PTT. A DTMF microphone, while convenient, is not necessarily required. Of course, don't forget your node computer! A Raspberry Pi is the perfect computer for this project and will enable you to transport this node anywhere with wired or wireless network access.
Don't believe me? Here's a diagram from the AllScan website outlining how to make one of these:
The Soundcard
Per usual with AllStar nodes, we'll use the CM108 soundcard available for under $5 on places like Amazon, eBay, AliExpress, etc.
As I mentioned above, the only thing to tack solder is a lead wire from pin 48 which will be the PTT wire. When this pin is grounded, this will send a signal to the AllStar software to toggle PTT on. The other modification needed is the removal of the SMD bias resistor R6. No other modifications should be needed and the PTT light is strictly optional.
To add on the TX and RX signals, you can tack solder connections to the audio jack rings.
The Microphone and Preamplifier
The board in question is the MAX9814 electret mic amplifier. This has a gain from anywhere between 40 and 60dB and will operate off of 5VDC.
The microphone I will attempt to use is from the Motorola SM50, an HMN1056D model. It has an 8-pin modular so a panel mounted RJ45 connector should work fine. Motorola microphones are interesting because they use biased voltage on the audio line. According to online sources, this voltage can range from anywhere from 5 to 9VDC. You'll need to adjust the voltage and the simpleusb menu settings until you're happy with the audio quality.
Most if not all Motorola mics have the same wire coding. The mic I'm using does not have DTMF capability, but this should be possible with a web UI like Allmon or Supermon where you can directly enter commands.
Here is the wiring strategy:
- Connect the GREEN mic cable (PTT) to the Mic Plug PTT (The fine COS wire coming from the CM108)
- Connect the WHITE mic cable to the Mic Plug Main Ground and the ground of the buck converter
- Connect the BLACK mic cable to the Mic Plug Mic Ground (The sleeve terminal on the CM108 Mic jack)
- Connect the RED mic cable to the Mic Plug Audio (The Ring terminal on the CM108 Mic jack) and also attach a 100-ohm resistor
- Connect the free leg of the 100-ohm resistor to a 2200uF capacitor to ground (Main Ground/WHITE wire) and to a 10-ohm resistor going to the output of the buck converter.
The Audio Amplifier
This section will utilize the PAM8302 amplifier board. Like the 9814, this will also run off of 5VDC. This is a Class D amplifier and will provide clear output audio to an external speaker or headphones. An LM386 could work, but many sources claim that these do not provide as much amplification as the 8302 chip and the sound quality is quite low.
SkywarnPlus
I will certainly be adding SkywarnPlus to this node as I have found it helpful and beneficial to me. I think that the developer of this did an excellent job writing and compiling this amazing add-on for your own AllStar node.
SkywarnPlus uses the publicly-available National Weather Service API to retrieve things such as watches, warnings, and advisories for pre-defined counties and areas. These are then relayed to the node which can transmit the alerts over the air, or in this case, over the loudspeaker we have attached.
Again, my warning stands about using anything but NOAA Weather radio for emergency alerts - DO NOT rely on anything that requires internet access. A natural disaster will most certainly take out phone and internet services first, so always make sure you have the latest updates using a solid form of reliable media. However, SkywarnPlus has proven to be very good at relaying messages rather quickly the minute EAS messages were issued when my original node was in beta testing. I had no issues at all and audio latency has never been an issue.
The other important thing SkywarnPlus does is make a note and cache of the advisory issuing and expiration times from the info pulled from the API. Once it comes time for the warning or hazard to expire, your node will announce an all clear message, regardless of internet connectivity or not since this data is cached on your node. If your unit is on a battery backup or a UPS, this can be crucial and beneficial.
In Defense of AllStar...
Recently I've been hearing of hams continuing to bash and ridicule the concept of AllStar, EchoLink, etc. Here's why AllStar is a good idea and why I'm an AllStar convert.
AllStar nodes are ridiculously inexpensive to create and can be made for less than $100, even less in some cases. Nodes usually have very small footprints, requiring less than a square foot of desktop space. For hams who live in restrictive areas such as HOAs, apartment complexes, or anywhere else where antenna placement is disallowed, AllStar can give you an option for exploring the world without ever getting on HF. Plus, the entire node can be run off of 5VDC - no more than what a USB power bank can supply! If you're a Technician, this is your ticket right here to make worldwide QSOs too without using 10 meters.
AllStar nodes, because of their small footprints, can also be taken on the road and can be used where internet connectivity is available. For example, you can use AllStar in a hotel room, at a vacation home, or wherever you are traveling to.
AllStar can also help give your old hardware a new life. Do you have an old commercial radio that can be rebanded safely and properly? If so, this would be a GREAT candidate for RoIP projects such as AllStar. Have an old laptop or mini computer that needs a home or purpose? Use it as an AllStar node!
Conclusion
Mobile apps like DVSwitch, iaxRpt, etc. have made accessing your personal AllStar node easier than ever if you're ever away from home. In order to connect you'll need to open a few ports on your home internet router, but this should be quite simple.
If you'd like to assemble your own AllStar node, I would like to recommend Freddie Mac's YouTube series, Ham Radio Crusader. He has a trove of amazing and interesting videos where he walks through AllStar node set up and add-ons. If you've got a lot of questions about the AllStarLink network, I'm certain Freddie Mac can answer it for you. Go check him out!
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