This might seem totally wacky at first, but bear with me a bit as this is experimental stuff and i know you folk like to experiment. The project: A SSB echolink node (don't stop reading its not as bad as you think!). I'm using a Raspberry Pi computer, a cheap USB audio card, and a homebrewed audio interface. To the best of my knowledge, only one other SSB node exists (on HF). The raspberry pi has accessible general purpose inputs/outputs (GPIO) that make interfacing simple. I used a 4n25 optocoupler and a 200ohm resistor to handle PTT duties. If you have a radio that can output a squelch-controlled signal you can turn the circuit around and feed the output to a GPIO input. So, with SQ and PTT properly isolated, we simply need to isolate speaker/mic into the sound card. One popular interface can be found for about $15 and its cheaper than buying the parts and building it yourself. But be warned: it functions, but not well. There will be common mode on the mic line. A few hundred ohms resistance helps. Using svxlink software as the core, the raspberry pi hums along nicely. It can bridge RF to the echolink network, bridge RF to RF, bridge local audio to anything, and even handle remote t/rx work and voter systems. Its good stuff. Why do this? I needed a project. Promote SSB use on 2m (and find someone to talk to!). Bring new hams to SSB domain. Results: Excellent. Really. Weak signals get into the VOS (voice operated squelch) with better SNR than the radio produces. I've no idea what audio processing is in-play, but connecting to my radio via echolink actually improves my ability to copy known weak stations. This doesn't mean they're instantly 100% copy, but there is a very noticeable and welcome improvement. RF-side stations report good audio/modulation. However, because of common mode currents on the mic line, close-in stations can detect hum. Besides this, remote stations report fine audio from echolink connected operators. Echolink-connected operators are amazed at the distances the station can cover with a modest beam and 25watts. Observations: The 600:600 audio transformers used for isolation are not good. I'm moving to another solution soon. There was a great deal of hesitation from my local SSB buddies about bringing this online. However, since bringing it online, it has become a major source of entertainment in our area. Its very well received now (no pun intended). There exists some bizarre condition that allows very weak signal reception with great clarity. The mechanism for this is totally unknown, but it requires a stronger signal source. When John (N4JS) is in QSO with my station, and I am connected via echolink, I can often hear other stations between johns words. The other station is exceptionally clear and noise-free, but only exists in the echolink node. It can not be heard in the receiver and it can not be heard unless john is transmitting. Other stations may produce similar results, but john happens to be closest to me, and if he has room-noise in his audio, its enough to wipe-out the other station. There must be some sort of mixing that the software is able to dig out and amplify, but for the life of me I have no idea how this works. The RF stations must be willing to chase the drift of my station since it can't be retuned remotely. So far they've been really good about this. Linking two echolink nodes together draws a crowd. Good operating practice becomes a must. Overall, this has been a really fun project and its brought a lot of life to our favorite SSB frequency. The system has proven itself capable, and has been a well spring of new ideas. If you have the means to experiment, I would love to hear about your experience.