The AN-1 is no longer made by Sony, it was replaced with the AN-12 which is basically the same antenna which I believe is also no longer available also, but may be available as NOS from some places. These antennas fetch between US$138 to $170 (Postage not included).
The roof side antenna houses the amplifier and a telescopic whip which is just 1.5 M long when fully extracted. It is powered by a 9V adapter or the equivalent in pen light cells. It is very easy to install and I had the antenna installed and up and running inside of 15 minutes.
Today, daylight DX was not particularly good as DX stations were few and suspect that propagation is not too good, so I was not able to do much of an acid test and compare it with my full sized passive vertical, but from the few stations that were present ,it do quite a good and decent job at pulling the stations in although there was obviously a bit more noise and fading when compared to the vertical. This was connected up yo my Lowe HF-150.
The true acid test will come this evening when I will listen to the night time DX and compare the differences with full sized antennas. Will report more.
However the AN-1 is a nice handy antenna to have around. If you can find an AN-1 or AN12, it may be worth considering to get one as a back up antenna for your listening system. There was also an AN-102 indoor active antenna made bu Sony.
There is also a whip antenna coupler for use with the AN-1, this slips over the whip antenna of the portable radio and connects via a cable to the antenna controller, so this is indeed a very versatile antenna.