Radio-over-IP module for FreePBX

As kind of a learning exercise on how to write modules for FreePBX, and to help our local Civil Air Patrol wing, I’m beginning the planning phase for a Radio-over-IP module for FreePBX that will add the capability, administered by FreePBX, of tying our wing’s PBX into its radio network.

Ideally, when this project is complete, someone should be able to call a PBX extension and be connected to an HF SSB channel to communicate with ground teams in the field anywhere in the state, or a VHF ground-to-air channel to communicate with aircraft.

So, before I go much farther, I need to ask… To y’all’s knowledge, has anyone done this, hopefully someone who wouldn’t mind if we build on the work that he/she has already done?

Certainly more than happy to donate back to the community whatever I come up with that I manage, by a long series of miracles, to get working.

And yes, I do understand that this is likely to be 80 percent Asterisk work and 20 percent FreePBX-specific work. Gotta start somewhere…

If you prefer to answer privately, it’s [email protected] or [email protected].

Eric /

Take a look at the DAHDI channel types, there already is an E&M radio interface channel type. The hybrid’s are 600 ohms so it’s no problem interfacing to a base stations remote control board.

There are issues (especially the SSB set) with having an operator in control of the base station. A hung channel would leave the base keyed.

Same issue on the VHF comm.

What do you envision, using DTMF to key or some type of VOX?

I have use these for public safety applications, same principal. They are not cheap.

You a pilot? There are several of us here including Tony and myself.

What do you envision, using DTMF
to key or some type of VOX?

Not really sure yet. A VOX setup would be ideal but I’m not sure how best to handle things like background noise which is prevalent in many/most CAP incident / exercise scenarios.

You a pilot? There are several of us
here including Tony and myself.

Yes, former Beech Bonanza owner (and Grumman Trainer, Cherokee Arrow, and 1/4 of a Beech Sundowner before that).

See for a not-so-short description of the FTDK (“Fork-Tail Doctor Killer”) we had for around 12 years.

Sold the Bonanza about four years ago and haven’t flown since. I haven’t flown for CAP for many years… too much paperwork and too many restrictions on what you can do… so I apply my 51 years of ham radio background in support of their communications including the PBX I just finished deploying.


I flew a 50’s vintage v-tail for Mission Air out of Jacksonville in the mid 80’s. It had the old instrument layout, swamp cooler, electric variable pitch prop (not constant speed) and even still had the flare launcher tubes.

It had character, nobody liked to fly it except me. It was fast and easy on gas. If I remember it had a mogas STC. I owned a straight tail Lance at the time. Fly a T210 today, too expensive, going to check out a Warrior a guy is selling block time in. It can get me from CLE to ATW (Appleton) where Schmooze is in about 2 hours and 10 minutes for half the cost of the T210. I will let you know how it works out. We are updating the SIP Station infrastructure in the Milwaukee data center at the end of the month and I am going to try the PA-28 for the first time. Fixed gear and prop, I am going to be horribly bored.

Anyway let me know how the plans go on the PBX/Radio interface. Anything I can do to help.