I just bought an ICOM AT-150 antenna tuner to go with my ICOM IC-735 (still looking for that elusive object, a moderately priced PS-55 matching power supply in good condition!).

The tuner has four antenna "ports" on the back. #1,2,and 3 all have SO-239 connectors and are clearly for 50 ohm balance line antennas/feedlines. The fourth port is simply a push-insert-release wire terminal. The manual states that this port may be used for attaching a long-wire antenna for general coverage reception. However, it also states that all 4 ports may be used for transmitting, as long as the SWR is already 3 to 1 or below.

Now I am curious, if this port is for a long-wire antenna (a balanced load, if the unit is well grounded, right?), does that mean there must be a balun inside the box, and does it have some ratio other than 1:1 (i.e. 4:1, 6:1) if it is to match the 50 ohm input to a high impedance output like a long-wire. Or am I confusing the terms "long-wire" and "random-wire". Would a "long-wire" antenna be a balanced load if it is resonant on some band?

I really would like to know what kind of antenna and/or feedline I could use on this single-wire port for transmitting. Is there a 50 ohm ladder-line that would be a match if I connect the other wire to the ground? Please help!