Here are my questions:

As I understand it, this antenna somehow tunes itself?? How does that work?

It's internal motor is controlled by the rig.

What cables go to the antenna -- obviously there's coax from the rig and I
assume it needs a power cable of some kind ????

Just one coax. The power and control signals are sent as RF to the
antenna. The control power and signalling pass through a duplexer.


I understand if I run a tri-plexer between the rig and the antenna I can use
this one antenna -- otherwise, run coax from the rig's antenna outputs to
respective HF, VHF, UHF antennas -- right?

That would be a duplexer. The 857 has only two antenna ports: HF+6m and
2m+70cm. Again, one suitable duplexer and one feed line to the antenna.


How did you mount yours? If you have photos on a website, please give me
the URL.

On a pipe, and no, I'm sorry I have no photos. The ATAS-120 uses a
standard SO239 mount.

How tall is the ATAS120 when fully-extended?

Not even 10" longer than when it's retracted.


Is it flexible so I could tie
it down the way we did the big ol' 72-inch whips we used way back when men
were men?

No it will not accomodate bending, under any circumstance beyond the
wind load of normal driving. The manual even warns you not to drive
while tuning it.


I'm planning to get the FT-857D, ATAS120, separation kit, narrow CW filter,
and the fancy mobile mike that can be used to control the rig. What else do
I need? Specifically, do I need an antenna mount, or, can I build my own
from aluminum plate?


Anything that presents an SO239 mount will do. Just keep it grounded,
vertical and sturdy.

Thanks.


I work all over the planet with my 857 with ATAS-120. You won't be
disappointed unless you expect dipole/yagi/large antenna performance.


Good luck!

Pat, VE3PMK