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Author Topic: Ic-746 Pwr Mod --results?  (Read 689 times)
WW5E
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Posts: 2




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« on: January 24, 2002, 03:16:58 PM »

I read where an adjustment to the pot R989, on the main 1 unit board (schematic 2, 2nd column of circuits, 3 row) adjusts the power out for TX on Hf.

My use for it is to provide higher excitor drive to a dentron clipperton amp.  I would like to drive it at 130 watts out.

Has anyone tried this mod?

Any caveats besides not going beyond X watts?

Any thoughts as to what would happen if I took the amp out of the circuit and used the 746 barefoot after this mod (i.e. without being the amp drive)?

Your help is appreciated.

Thx, Craig WW5E

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WB2WIK
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Posts: 20612




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« Reply #1 on: January 24, 2002, 06:31:49 PM »

I wouldn't do it, to pick up about 1 dB, which is all you can pick up from this change.

The IC746 is rated 100W PEP output and is verified at that power level to meet spectral purity requirements, and to have an operating warranty.  At a higher adjusted output level, the purity requirements are likely not met and the warranty is likely voided.

The real problem is the Clipperton had untuned input, which can create a pretty fair mismatch to its exciter, further reducing the purity of the driving signal.  If you crank up the IC746 drive level, the mismatch, and drive signal impurity, will not only continue to exist, but actually get worse.  You'll probably sound lousy on the air.

I wouldn't bother.  A far better choice would be to find a buyer for the Clipperton, and try to find a replacement amp with tuned input that is more easily driven (and more cleanly driven) by the IC746.

WB2WIK/6
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K4PDM
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Posts: 37




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« Reply #2 on: February 06, 2002, 02:49:11 PM »

I would think that the internal tuner in the 746 would allow you a good match into the amp. I used the tuner in my TS-940S to match the WARC band inputs on an Amp Supply amp--the internal tuner handled it easily.
That is, assuming the other post is correct--that you don't need more power, just a better match!
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