Hi !

The 'D' indicates which band is selected for DATA (eg APRS), ... and has nothing to do with duplex mode :-)

Regarding duplex: when you press duplex then the THD7 is immediately into duplex mode, eg band A 145.920 and band B 435.300 Mhz.

Select band A (a/b) if you want to transmit on A. Select band B (a/b) if you want to transmit on B.

While you transmit on A, you still hear sound, coming from band B. This way you can hear yourself back via eg AO51. (you may need either external mic or a headphone in this set-up)

If you go to http://www.pa3guo.com, click on OTHERS in topmenu and then DOWNLOADS in left menu you get sat-memories for the THD7 which you can quickly donwload via a PC into the THD7.

Success ! Henk, PA3GUO http://www.pa3guo.com