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Re: [Amps] LDMOS HEAT SPREADERS

To: amps@contesting.com
Subject: Re: [Amps] LDMOS HEAT SPREADERS
From: Kevin <kstover@ac0h.net>
Date: Wed, 31 Aug 2016 18:36:50 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>


On 8/31/2016 9:49 AM, Manfred Mornhinweg wrote:

In the PC overclocking scene, a lot of snake oil is being sold.
Not necessarily. My quad core AMD running at 3.5GHz per core, full tilt, will dissipate 135W. The Zallman cooler I have on mine will keep the CPU temp in a range of 32-35 C at full output. It's a very large, round, brazed up combination of heat pipes and copper radiator fins surrounding a 135mm diameter fan.
I would first do a reality check on any CPU cooler rated for several hundred watts, before using it for a real high power application.
The newest AMD processors are eight core and will dissipate 225W when run full out. Want to stress a CPU and it's cooler...give it to a bunch of gamers. If it passes muster with them it's pretty good. This is how PC water cooling got started. Alienware was the first manufacturer to offer water cooled gaming rigs. I believe they were also one of the first companies to try liquid N2 cooling. They got a 125% overclock running stable with liquid N2. We used to dance in the street when we got 30% with air cooling. I got an Intel Celeron 300A up to 450MHz, 50% overclock, but it took some serious messing around with CPU and memory voltages, CAS/RAS memory latency, etc.... These days they hook up a water cooler and get that all day long.

Would I recommend trying to cheap out and use PC coolers for cooling an LDMOS amp. Of course not. anybody who does so needs a good public slapping. The stuff being sold in overclocking circles isn't snake oil. If you sell crap in the "PC Enthusiast" market you'll be out of business in a week, two tops. They can get vicious if they think they're getting screwed.

By the way, the 1dB compression point on a typical LDMOS package like the BLF188XR with 50V is about 1100W out.
I'd use a pair and keep each chip in the 750-800W range.


--
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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