I would suggest a RigBlaster PLug n' Play. They make an adapter that plugs directly into the zillion pin accessory plug on the back of the 706, so you don't need to mess with the microphone connector at all. It's a pretty neat installation, just one USB cable and the two audio lines to the computer. You can buy other adapters to use it with several different radios. Here's a web page with the details on the adapter required: http://www.westmountainradio.com/pnpradiomatrix.php You can also do CI-V control from this same adapter. The only things I never had luck doing was using the CI-V and doing CW at the same time - a separate CW interface like the WinKeyer would be a good investment.
I run a net using Olivia 16/500, and it works well under utterly horrible conditions. I can copy signals I can't hear or even see on the waterfall display. The mode has so much redundancy and forward error correction that it is fairly immune to most bursty static. It is, however, very slow. There are MANY Olivia nets springing up around the country. Google 'NBEMS' and you should find lists of them. Some of these nets use other versions of Olivia and other modes.
PSK31 is the most common conversational mode. JT-65HF is used for making brief contacts under extreme conditions. I used to run 2-3 watts to a piece of wire hung in a tree outside my window on JT-65HF and I had QSO's with people all over North America and Europe on 20 meters and higher. WSPR is another interesting very low power mode.
One very important hint: turn the AGC off when doing digi modes, and use the RF gain to adjust the sensitivity. This is really helpful when the band is crowded, and there is a mix of weak and strong signals. With the AGC on, the strongest signal will wipe out the weaker ones.
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