Icom 746 and external ant. tuners - Elmers Forum at eHam.net

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eHam.net Forum : Elmers : Icom 746 and external ant. tuners

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Icom 746 and external ant. tuners	Reply
by K4AXX on July 10, 2003	Mail this to a friend!
On a particular site which goes into quite a lot of operating detail re: the Icom 746-http://www.skysdaughter.com/icom746-faq/ reference is made to using an external tuner (not the AH-4)with the rig. According to what is written here Icom supposedly says that no external tuner should ever be used as it it might damage the built in one. On the other hand, no reason is given, and other hams have claimed to using external tuners with the 746 without problems. Does anyone have any thoughts on this please. It would be much appreciated. Thanks.

RE: Icom 746 and external ant. tuners	Reply
by KC1MK on July 10, 2003	Mail this to a friend!
You can use an external tuner with the 746, just make sure you disable the internal tuner. Otherwise, the internal tuner will "chase" the external tuner as you adjust the external tuner and damage can result. I use an external autotuner (LDG AT-11MP) with my 756ProII and it works very well. The AT-11MP has a much wider matching range than the ProII's internal tuner. The AT-11MP is rather noisy when it is tuning, but it tunes quickly and you get used to the noise pretty quickly. It will interface with the ProII with an optional cable and you can use the Tune button on the ProII to activate autotuning in the AT-11MP. I'm not sure offhand, but the AT-11MP may also interface similarly with the 746. Jeff, KC1MK

RE: Icom 746 and external ant. tuners	Reply
by K5LXP on July 10, 2003	Mail this to a friend!
That's a nice page, I hadn't seen it before. I was playing with a doublet that had way higher than 3:1 SWR and knew it was beyond the bounds of the internal tuner, so per the text in the faq you referenced, I had just transmitted a 10W or so carrier, tuned the antenna with my tuner to 1:1, then pushed the 'tune' button on the '746 to assure it was happy. Worked fine for the few times I did this, but it's easy to see how you could fry the 746 transmitting full-bore into a tuner that wasn't pre-tuned this way. Once I tried to 'touch-up' the tuner and the '746 immediately tried to re-tune it with the internal tuner. It's no suprise the factory doesn't endorse the use of an external tuner, it can be overwith in a flash if you're not careful. Mark K5LXP Albuquerque, NM k5lxp@arrl.net

RE: Icom 746 and external ant. tuners	Reply
by K0BG on July 11, 2003	Mail this to a friend!
Jeff, you're correct the LDG does have a wider range of matching than the internal unit, but neither one has the range of the AH-4 or one of the SGC units. That said, if you really need the matching range the LDG offers and you're using coax to feed the antenna in question, I think I'd change antennas or at least mount the tuner outside to minimize losses in the coax. Just a thought. Alan, KØBG

RE: Icom 746 and external ant. tuners	Reply
by K4AXX on July 11, 2003	Mail this to a friend!
KOBG- The problem with the AH-4 (and what a great tuner it is) is that its made to feed a wire and to work only with the Icom line. 73. Thanks to all for your input on this :)

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