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Author Topic: Question about Henry 2002A Amp - low power output  (Read 2037 times)
KB7TLE
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Posts: 2




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« on: October 10, 2010, 02:06:48 PM »

I recently purchased a Henry 2002A amplifier for 2 meters.  It is rated at 1KW PEP output for SSB operation.  However, I am only able to achieve 350 - 400W out as measured with my Diawa power meter.  

When I drive the amp with just under 50W, I show a grid current of 30 ma and a plate current of 500 ma.  The filament voltage is approx 13.5 volts.  Plate voltage is 2400 VDC for SSB operation.  

Because the grid and plate currents look good, I would suspect a soft tube.  However, I have tried a second tube with similar results.  Is there anything else that could cause this low output problem, other than two bad tubes?
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AD5X
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Posts: 1432




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« Reply #1 on: October 10, 2010, 03:50:56 PM »

I suspect that you aren't using a true peak-reading wattmeter.  350-400 watts is more like what you'd measure with an average reading wattmeter for a 1000 watt PEP SSB signal.  Actually, I'd expect more like a 250-300 watt average power reading unless you have a lot of compression.

Phil - AD5X
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N4RSS
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Posts: 260




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« Reply #2 on: October 10, 2010, 06:35:13 PM »

I suspect that you aren't using a true peak-reading wattmeter.  350-400 watts is more like what you'd measure with an average reading wattmeter for a 1000 watt PEP SSB signal.  Actually, I'd expect more like a 250-300 watt average power reading unless you have a lot of compression.

Phil - AD5X

In one way, I hope you're wrong but I fear you're correct Shocked
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KB7TLE
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« Reply #3 on: October 10, 2010, 08:11:44 PM »

I'm looking again at the specs from the Operating Manual.

Output Power:
1000 watts PEP SSB
2000 watts short pulse
600 watts FM
400 watts continuous carrier

I'm confused by the termonology.  What power reading should I expect to measure when I hard key in CW mode? 
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WB2WIK
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Posts: 20611




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« Reply #4 on: October 11, 2010, 10:07:24 AM »

I'm looking again at the specs from the Operating Manual.

Output Power:
1000 watts PEP SSB
2000 watts short pulse
600 watts FM
400 watts continuous carrier

I'm confused by the termonology.  What power reading should I expect to measure when I hard key in CW mode? 

If you have a still AC power line (preferably 240V), you should see over 600W carrier power on CW.

Try it and see what you get.  And whatever you get, when the amp is fully loaded to max power on CW, what's the high voltage read (key down, full output)?
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WY3X
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Posts: 768




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« Reply #5 on: October 11, 2010, 11:48:08 AM »

Do the math. 2400 volts times .5 amps is 1200 watts INPUT (not output). Output is probably around (guessing) 50% of input, so 600 watts out sounds reasonable. You'll need to be in FM mode or CW key-down to see this level, but don't do it for too long because it will stress the tube. Make sure you're tuning up into a dummy load, because if you're using an antenna, it's possible that a small mismatch may be throwing your readings off. Also, if you're + or - 50 ohms at the point where your wattmeter is inserted in-line, it might be reading a tad off. Several small errors in reading can add up to one large mis-reading. Also, make sure your Daiwa wattmeter is set to read RF at 2M. If it's an HF wattmeter, you could be way off on your reading (but normally too high if this is the case). -WY3X
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