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Author Topic: AL-80A Power Metering  (Read 1454 times)
W9DJ
Member

Posts: 9




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« on: January 08, 2008, 06:40:55 PM »

My 17 year old AL-80A (original tube) has developed a problem. On 160 and 80 the power output meter internal to the amp indicates only 200-300 watts out at 400 ma, 2500V, with 150ma grid current, while an external meter shows about 600 watts out (all measurements cw). However, this happens only on the antenna (via a Ten Tec autotuner). Everything is fine on the dummy load, and on the antenna at 40 meters and higher. I have checked the antenna, and replaced the weathered feedline to no avail.  I am using an external balun, which I have not replaced.  SWR at the input to the tuner shows no worse that 1.1:1. The antenna is an off center fed 160M dipole, with a short low loss coax run to an external balun, then ladder line to the antenna. The change happened suddenly. Any ideas what is going on?  I have also had reports of distortion, but intermittently, even though the amp seemed properly loaded, other than the low power output indication on the internal meter, based on grid and plate current and the external power meter reading.  I have cross checked the tuner swr meter against the one in the exciter, and they agree.  
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W5RKL
Member

Posts: 1113




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« Reply #1 on: January 09, 2008, 07:07:48 AM »

My first thought is an intermittent ground either
in an PL-259s or some other ground connection.
I would check all grounds on all PL-259s and
any other grounds you may have. Just a thought.


73
Mike
W5RKL
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