Using the ATAS-100 antenna together with FT-817.

The ATAS-100 antenna has designed to use with YAESU transceivers equipped for the ATAS system, such as
FT-847 and FT-100/-100D.

As I also have YAESU FT-847, it was easy to find, that ATAS-100  becomes longer (for operation on low HF bands),
when +12,6 volts comes to the motorized tuning system and +8 volts to make it shorter.
Than I build up very small and simple unit:

Of course, it possible to use only one DPDT momentary center-off switch instead of press-button and switch,
but I find my solution more operable.

Adjustment of ATAS-100 to the operational band I made as follows.
Let's imagine, the antenna in most collapsed position. And I want to work on 20 meters band.
I put switch S2 in "UP" position and press button S1. Then 12 volt coming through coaxial cable to the drive motor
in ATAS-100 and antenna started "grows". At the same time I listening noise on 20 meters band.
When the noise is rise up to maximum, I release the button. Sure, I am close to the resonance frequency.

To be 100% sure, just check SWR by a build-in meter (Menu row 9|B|MTR-SWR) while transmitted and make final
adjustment to the best SWR, if necessary.
For example, I want after operate on 10 meters band, I put switch S2 in "DOWN" position (to make antenna shorter)
and press the button S1 again. Than +8 volts coming to the ATAS-100. Simultaneously listen to the noise in the headset,
while on 10 meters band. And repeat all above mentioned procedures.
After several times of training you will find out the moment, when release the button on each band, regarding to the noise level.
The best way for adjustments - to transmit "dots" in CW mode.

Of course, this is not so quick, but it is a way to use ATAS-100 not only with FT-817, but  with the another transceivers.
I tried also with my KENWOOD TS-2000, and it works perfect. Just remember, that  separating capacitor between BNC and PL
connectors must keep high RF voltage. I am using mica capacitor, 0.1 microfarad x 400 v, but I never transmit through this unit more, than 20 W.