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So my idea is I might use a keyboard to enter text. I would use an Arduino to control the ham radio. The problem is that I have no idea on how to use the Arduino to control the radio. Also, what speed would I expect and what software would I use? Is there Arduino code for this purpose?

-KM6MCM

Glenn W9IQ
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itisyeetimetoday
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    what kind of packet radio are you referring to? As far as I know, none of that series "speaks" APRS by itself, so you'd need your external controller to generated the AFSK tones. Whilst possible with an arduino or the like – wouldn't a simple "proper" computer like a raspberry pi or so not be the better choice here? You could basically run any ham software for linux on that, and there's certainly plenty of choices for APRS then. – Marcus Müller Jul 09 '18 at 06:18

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As far as I know, none of that series "speaks" APRS by itself, so you'd need your external controller to generated the AFSK tones.

Whilst it's possible to generate AFSK at such low rates with an arduino or the like – wouldn't a simple "proper" computer like a raspberry pi or so not be the better choice here?

You could basically run any ham software for linux on that, and there's certainly plenty of choices for APRS then.

The Raspberry Pi Zero would absolutely suffice in terms of compute power, you just add your keyboard, and USB sound card that you connect to the baofeng, and would be done (likely, you could also hook up the headset's PTT contact to a GPIO to). With a fully blown raspberry pi, you could even get models that include the audio interface.

Both the Pi Zero as well as the larger Pi 3 and Pi 2 come in variants with integrated bluetooth connectivity - a good idea if you want to connect say a wireless keyboard.

Personally: AFSK 1200bd is so simple, you could absolutely implement that simply setting the PWM units of the pi to different frequencies (or worse, just bitbang GPIO). That way you could basically implement APRS on a 5$ - 10$ Pi Zero without additional 5$ on a USB sound card, but then you'd have to come up with your own software that implements the APRS stack. In case you'd always wanted to work with the linux kernel, you could certainly add that as a physical network interface for AX.25 packets. If I'm correctly educated, then G4KLX implemented AX.25 as part of the network stack in the Linux kernel decades ago, and it's been there ever since.

You see, using a full linux computer like a Raspberry Pi (Zero) or one of its many, many competitors solves many problems at once: No need to write your own keyboard driver (that's actually hard to do on a microcontroller like the arduino), no big hassle implementing the physical (so, AFSK) side of things, and as a big bonus, AX.25 integrates as protocol, just like IP, into the operating system and you can thus leverage a truckload of existing software to get your packets.

Another approach would be using you smart phone's headset port to talk to the Baofeng's headset port – I bet "there's an app for that" and all you need to do is find a way to do some audio level shifting, maybe, and some way to activate transmission. Your baofeng can probably do that already, if it has voice activity detection.

Marcus Müller
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  • Thank you for responding! Do you have a tutorial for what you mentioned above? Also, do I need a license above technician for AFSK? Again, thank you for your time. - KM6MCM – itisyeetimetoday Jul 09 '18 at 23:35
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    There is this project: https://github.com/markqvist/MicroModemGP which implements APRS on an Arduino / ATmega328 microprocessor. A technician license should be fine to operate on 2m/144MHz. – Manawyrm Jul 10 '18 at 09:33
  • @TobiasMädel Thank you for responding! I was referring on tutorials on the raspberry pi side since the Arduino seems to be underpowered. Also, how do I control the Baofang radio? I also want to change the channel, not just control what audio gets played(since that is solved by plugging in a 3.5mm audio cable) – itisyeetimetoday Jul 10 '18 at 17:57
  • @itisyeetimetoday well, I don't know whether the radio in question supports channel control over any kind of external input at all. – Marcus Müller Jul 10 '18 at 19:24
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    No, the Baofeng unfortunatly has no method for CAT control. So channel switching isn't possible, unfortunatly. – Manawyrm Jul 11 '18 at 06:30
  • @itisyeetimetoday if you want that, by the way, maybe you really want some kind of SDR instead of a Baofeng handset? It's not really like you need the narrowband input on the analog side, anyway, in most scenarios where you'd do APRS, and can filter digitally from an observation that spans all channels that could possibly carry packets *at once*. But, tbh, I know maybe a bit about SDR, but not what hardware a ham would want for that application (seeing that's more than just the radio interface, but also incorporates TX amplification, probably). – Marcus Müller Jul 11 '18 at 06:34
  • @Marcus Müller The price and compactness is what I really need. I need the ham radio to run of a large solar panel or battery, so I am afraid that the power draw of the SDR might be to high. By the way, I also want to send to signal directly to each other(not through a satellite), because the ping is already in the 2000ms. Also, I hope to be able to transmit images in the mbs. – itisyeetimetoday Jul 11 '18 at 20:42
  • That argument doesn't work. Guess what, under the hood, that baofeng *is* an SDR, it just doesn't allow you to do what you want. – Marcus Müller Jul 11 '18 at 20:49