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Author Topic: Icom AT-120 Antenna tuner (Any Ideas?)  (Read 1890 times)
N4SNL
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Posts: 68




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« on: June 08, 2002, 04:13:54 PM »

I have an AT-120 but know very little about it and would like to use it but cannot find any info on the net and Icom is taking forever getting back to me. I got it at a ham fest and it came as is and no manual. I have an Icom 735 and would like to mate it with this unit but I need to know what goes where. 1 wire  bundle coming out with coax, key, (antc), 13.6,and start as written on the inside curcuit board. I figure I will need a box with a special plug unless someone knows how I can hot wire it so to speak. Would really appreciate any info on this if possible. Thanks, Scott N4SNL
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KA4WJA
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Posts: 703




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« Reply #1 on: June 08, 2002, 06:14:34 PM »

Scott,
Ideas???  How about the definative answer.....

The Icom AT-120 is Maritime HF remote automatic antenna tuner ....(In "old salt" vanacular, it's an "antenna coupler"...)

  Icom made a couple of different versions, during their production lifetime (1980's)....

1)
The "original" AT-120 was designed for use from 2mhz - 23mhz ONLY...(although it MAY operate beyond that range, depending on antenna length.....it probably won't....) at RF power levels of 150watts Cont. Duty!!!
And was designed for a antenna wire length of 23' to 90'.........(although in actual use, could be used with shorter antennas on freq above 8 -10mhz...)

2)
The revised version AT-120 was "updated" to cover 2mhz - 30mhz, and was spec'd very similarily......

3)
 After the revised version of type AT -120 came the
Icom AT -130.....
(very similar to the 120, but a bit different "tuning procedure"....if I recall correctly.....)

These tuners had their "amateur radio counterparts"..the Icom models AH-2,  AH-3(I think???),  and now the AH-4.......

The Icom IC-735 could be attached to the AH-2  (or the AT-120) using the "optional Outboard Tune Module"...
Which was just a push button or two, and an LED or two, in a small alum box that attached to the front edge of the side panel of the IC-735 and a small cable from this "tune module" to the acc. jack on the rear panel of the 735......
The "4 - wire cable" from the tuner attached to this "tune module"......
My recollection (from 20 years ago...) is that the
"4-wire" cable carried the B+ (12-14vdc), "tune", T/R line, and Huh?? (antc)

Regardless of the "exact" wiring nomenclacture.....
The AT-120 should work very similarily (depeding on "version") to the AH-2.....

As far as "hot wiring it"......
And all you need to do is activate the "tune" function, with some sort of switch (momentary contact, etc.Huh??) and apply 3 - 10 watts of RF drive power to let the tuner "tune"......
And I believe that the "antc" contact closes when the "tune" is complete......(NOT exactly sure of my memory.....BUT with what I've given you here, you should easily be able to figure it out the rest of the way!!!!)

Good luck....

73,
John,   KA4WJA
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KA4WJA
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Posts: 703




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« Reply #2 on: June 08, 2002, 07:44:50 PM »

Scott,
One additional piece of info....
Icom reps stated that the AT-120 (2nd version) was similar to the AH-2.....but there were some differences....
The specs show that the power handling for the AH-2 was only 100watts....but it should be capable of operating with a shorter antenna than the AT-120.....
(more tune "possibilites"Huh?)

The newer AH-4 is strictly a "ham radio quality" tuner...
It's good, BUT not nearly as rugged as the AT-120!!!!

I thought I should clarify, that the "amateur radio counterparts" generally will tune using a broader range of antennas.....AND have a lower power handling rating....
The AT-120 is built more for a higher demand application (maritime, etc...).....

I hope this helps....


Good luck.
73,
John, KA4WJA

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K9CF
Member

Posts: 33




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« Reply #3 on: June 15, 2002, 09:58:17 AM »

check out www.qsl.net/k9cf
I've got a file there that could help.
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