Andersons Abroad
Technology

Phone or Internet Voice calls via SSB?

Rich

So I’ve been reading about SSB, SailMail, and Pactor modems, as well as other technologies developed over the years to handle small email communications via radio or satellite.

image courtesy of SailCom Marine
image courtesy of SailCom Marine

With an SSB (Single Side Band) radio, such as the Icom IC-M802 transceiver, you can communicate with other SSB users at distances well over 2000 miles.  Adding a special modem you can actually transmit data over the radio, but due to the extremely limited bandwidth available using this technology, weather reports, and small email communications are about the only feasible use of this technology.

Today I read about the newer Pactor 4 protocol which doubles the data bandwidth of the SSB modem from 4kbps to about 8kbps.   When I read about this update, I suddenly wondered if that might be enough bandwidth to use Skype or some other Internet voice service to communicate with family and friends back at home from a boat in the middle of the Pacific.

Consider that 8kbps, while very fast for an SSB radio connection, is still extremely slow compared to home DSL, Cable, FiOS connections (as well as Satellite).  The typical DSL connection provides between 1mbps (1024kbps) and 12mbps (12288kbps) while Cable/FiOS offer speeds of 15mbps (15360kbps) to 100mbps(102400kbps).  So this latest Pactor 4 SSB modem connection achieves 1/128th to 1/12800th the performance of a home connection.

After a little research I discovered that some Satellite phones use an audio codec (compression/decompression algorithm) called IMBE or AMBE (depending on the service) which supports quality audio at 3-5kbps.

So I wondered if it would be possible to implement an Internet voice-to-SSB service using some software using AMBE to encode the audio.  Unfortunately, it turns out AMBE is patented and requires quite hefty licensing fees that I’m just not willing to pay.  The good news is, some open source dudes created a similar codec called “codec2” which provides voice transmission at rates as low as 1.2kbps.

It seems like I should be able to implement some sort of service for sailors with SSB using codec2 to chat with family and friends via the Internet.  This is something I plan to look into further and attempt to build.

Anyone have used SSB and Pactor modem hardware I can borrow?