I've been looking for a decent auto-tuner ever since I've started working remotely with my rig. As you might recall, I had been using a Palstar AT-2K (which is a manual tuner) for my HF tuning needs. The Palstar worked great, it would really tune a fish (yeah, ok - that's a really bad pun...) Really though, it did a fantastic job with my doublet.
I had tried using my LDG IT-100 (I think that's the right model), but the auto-tuner would not get close to what the Palstar could tune. In fact, it performed so poorly with my awful configuration, I was VERY concerned that ANY auto-tuner (with the exception of the Palstar and Alpha auto-tuners!) would not perform. A concern that I will tell you is now a distant memory!
I had read a few articles about people using the AH-4 tuner in a "non-supported" configuration. In short, they were using it as a tuner SPECIFICALLY for doublet work. Here is a link to a really good website dedicated to it's purpose: K9EQ's AH-4 General Information
The picture (from the previous website) shows pretty much how my connection is configured as well:
Instead of using the "Ground" connection, you simply connect the "other" side of the twin-lead and you are in business :)
I would really encourage you to read the technical details listed in the website earlier - the author (K9EQ) has done a very nice job describing his setup and how he made his situation work for himself.
Anyway, I did the very same thing in my shack. I removed my Palstar and my Baluan which left me with an ICom 9100, AH-4, and some twin-lead coming into the shack. Coax run from the 9100 to the AH-4, control cable run from the 9100 to the AH-4, and twin-lead connected from the doublet to "both sides" of the AH4-4 and I was done.
I switched the tuning mode to the coax with the AH-4 connected and the 9100 immediately showed a connection to an "External" antenna. Pressed the tune button and heard a bunch of clicking and clacking and then the magic letter appeared on the display - "Tune" (meaning a match had been made)!
I tried every band I could and the only place I could not get it to tune was at the very bottom of 160m. Everywhere else, I can get a match. That's great news - this means that I can really use my remote setup to the best of it's ability. I can remotely control the power level, the operating frequency, and tuning the antenna.
I short, it works very well and I can now stop dreaming about the Palstar and Alpha auto-tuners! This little ICom does the trick nicely.
73 de KJ4WLH