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Saturday, 26 May 2018 09:58

5GHz Power Amplifier Temperature Test

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I'm hoping to use my new power amplifier during the next BATC activity weekend in June. First though a temperature test was needed as it's not very efficient. Testing power consumption a couple of weeks back it was using 85 Watts to generate 10 Watts RF output.

Following discussion with a knowledgeable friend I added a small Papst fan found in my spares cupboard. Advice was to have it cut in at about 60 degrees C; so I bought and fitted a normally open bi-metal device.

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Initially I thought about buying some of the adhesive temperature strips and couldn't believe the cost; luckily I was loaned a measuring device with a probe which tucked nicely between the temperature sensor and one of the heat sink fins.

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Starting at 20c which was shack temperature at breakfast time I fired up the amplifier with loads on input and output; at the same time running a stop watch. From an earlier brief run I had suspected the sensor and fan would be a safety feature only, I figured I would be OK with short overs.

It took 20 minutes and 40 seconds for the fan to kick in and the probe showed that it was exactly 60 degrees. After 2 minutes with the fan running the probe temperature dropped to 54 degrees; and 51 degrees after 5 minutes. Confident the amplifier is protected I'll run it in June.

There is one more issue to deal with; and that's where and how to mount the heavy lump without using long cable runs. Maybe the subject of another post.

73

 

Read 435 times Last modified on Saturday, 22 December 2018 10:22

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