I hadn't tried V/U with it either, as I use a separate dual band 2m/440 antenna. I run my ATAS100 with a 706, so only connect it to the HF/6 port. Anyway, upon reading your post I hooked it up to my MFJ259 to test the 2M response of the ATAS. It didn't matter if the coil was fully extended or retracted, it didn't work either way! Not sure if it's due to the particulars of my setup, or it just plain doesn't work. Couldn't test UHF, as the '259 stops at 170MHz. I was going to guess that the ATAS represented a quarter wave on 2M and a 3/4 wave on 440, but not seeing any useable resonance at 2M I'm not sure it would be any better at 440. Now I'm glad I didn't bother getting a diplexer for the 706 and went with a separate 2M/440 antenna. If the problem is caused by the way I mounted it, it shows that the ATAS is very ground plane sensitive and that should be tested if V/U operation with this antenna is important to you.