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Author Topic: Yaesu FT-3000M power adjustment  (Read 1208 times)
K4JC
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Posts: 76




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« on: April 21, 2009, 05:09:57 PM »

I have a Yaesu FT-3000M that is showing only 55 watts into a dummy load on high power (should be 70 watts). I have no service manual available. After a Google search I have found several references to how easily the problem is corrected, but no one says how to do it! Hopefully it's just a quick trimmer pot adjustment. Anybody know the procedure? Thanks in advance!
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KB1LKR
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Posts: 1898




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« Reply #1 on: April 21, 2009, 09:03:39 PM »

56 Watts on a good (e.g. a Bird 43, w/ a 100W slug) wattmeter w/ a current NIST (or equivalent agency) traceable calibration cert? If not, I'd leave well enough alone as your within 1dB of spec for the transmitter +/- your instrument measurement uncertainty.

A calibrated, traceable Bird 43 or similar is +/- 5% F.S., so +/-5W w/ a 100W element, +/-12.5W w/ a 250W element, etc., so I'd just err on the safe side and tweak  a 70W to 65W (-0.3 dB) out, with anything less, e.g. a used 43 & slug, lacking a current cal cert, a run of the mill amateur power meter, (+/- 10% F.S. or worse) etc. I'd leave it be.

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WA3SKN
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Posts: 5558




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« Reply #2 on: April 22, 2009, 07:44:16 AM »

Why? Are you having trouble making contacts?
By running it a lower power those final transistors are in all probability just "loafing" along and can take a lot more abuse.  Do you really need 70 watts?

-Mike.
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N2IK
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Posts: 220




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« Reply #3 on: April 22, 2009, 06:13:54 PM »

Before you adjust anything, check the DC supply voltage at the unit under load. If it is not 13.8 or close to it, adjust the power supply until it is, then make the power measurement. Be sure you know the accuracy of your power meter. 73 de Walt N2IK
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