I need to transmit digital data, from an Arduino, Raspberry or alike, but using VHF band (aprox 150 MHz), would anyone care to suggest a cost effective device to use as transceiver? 10W would be desired, but 5W will also be accepted.

  • $\begingroup$ Is such a transmission like that legal in your country. I know nothing of the Chili amateur radio licensing and bands allowed for VHF. How about one of the digital modes (PSK31, etc.) and if your data is not "text", that is, binary, first do a binary to text conversion maybe using something as simple as Base64. $\endgroup$ – K7PEH Dec 29 '16 at 2:38
  • $\begingroup$ @K7PEH actually data IS text 😉 .. but I'm not worried about protocol nor encoding, but how to "feed" and send the data using which device. This needs to be escalable, as the sample proof of concept will involve around 5 base stations, but once in operation mode, it'll cover hundreds of stations $\endgroup$ – Gonzalo Vasquez Dec 29 '16 at 9:36
  • $\begingroup$ sound like this is not amateur radio which this forum is about but you can still use software used by amateur radio to encode text per protocol rules like PSK31 (Note, I am not suggesting that PSK31 is the protocol to use, just that it is an example of various protocols available). The coding though in the computer creates an audio stream which is then sent as audio (e.g. audio in of transmitter) to the radio which then transmits using either SSB or narrow band data modes if supported by the radio transmitter (my K3 does this). This is not the only way this can be done. $\endgroup$ – K7PEH Dec 29 '16 at 16:39
  • $\begingroup$ I suggest you google and research protocols such as PSK31 and the techniques of interfacing software in a computer with the radio you have available. In most cases, the interface is audio in/out ports on the radio. Most modern transceiver have these ports and if not you can make use of the mic input and speaker output. There are also interface devices that handle this for you but used primarily for HF comms and not VHF. Signalink by Tigertronics is such an interface device. $\endgroup$ – K7PEH Dec 29 '16 at 16:44
  • $\begingroup$ @K7PEH Thanks for the protocols suggestions, that would help indeed, but what I'd like to really know is which VHF device (hopefully with RS232 or TTL interface), as the ones we already have (and work as desired) are Kenwood NX700 and NXR710, but as they won't be used for voice comms, those are a bit overpriced for their actual use $\endgroup$ – Gonzalo Vasquez Dec 29 '16 at 18:17

I once spent a bit of time getting packet radio going over VHF using a Raspberry Pi and Direwolf as the modem. It worked fine using a couple of cheap Wouxon handhelds. (I've heard that Baofengs don't work as well due to the time it takes to break the squelch.)

The instructions I used are here: https://andrewmemory.wordpress.com/2016/03/31/turning-a-raspberry-pi-2-into-a-packet-station/. In short, set the Pi up as a packet node, then use Direwolf and kissattach to provide TCP/IP over packet into a sound card. Too much for an Arduino, but should be fine on a Pi.

They required a Signalink to do the PTT, but I think Direwolf can do the PTT itself with an appropriate cable.

I'll leave the legalities of it up to you - but packet radio is designed for multiple stations, can route traffic through nodes (and in fact is TCP/IP), and appropriate Wouxuns can transmit 1200 baud packet at 147 MHz, so should be able to handle it at 150 MHz.

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    $\begingroup$ exactly what I'm looking for...packet radio with a Raspberry Pi 3...I'll have to check your instructions in detail...hope it works! Thanks a lot! $\endgroup$ – Gonzalo Vasquez Dec 30 '16 at 23:04
  • $\begingroup$ Could you please elaborate a bit on the Signalink and it's use? $\endgroup$ – Gonzalo Vasquez Dec 30 '16 at 23:04
  • $\begingroup$ The Signalink (tigertronics.com/signalnk.htm) detects an audio signal and triggers a PTT line. There are other devices that do similar things, but I think Direwolf can trigger the PTT line directly. $\endgroup$ – user3486184 Dec 30 '16 at 23:14
  • $\begingroup$ Direwolf (github.com/wb2osz/direwolf) seems just great! A part of the "puzzle" that I was looking for. Haven't read much about it yet, but does it actually need an USB sound card for the Raspberry or, it uses the GPIO pins for connecting to the transceiver? Do you know if there's any chance of extracting received power info from the received data? Asides from the received data itself I do need to know if there's been some change in the input power, as we are using stationary base stations, and relevant tx power changes may indicate adverse problems, so we'd like to monitor that too. $\endgroup$ – Gonzalo Vasquez Dec 31 '16 at 1:11
  • $\begingroup$ If you want to get more low-level, google 'hamshield'. It is a 500mW Arduino-based VHF/UHF radio shield. hamshield.com. I'm not affiliated with them but have been watching their progress on Kickstarter. $\endgroup$ – captcha Jan 2 '17 at 21:22

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