The DL guys that built that gizmo had it clamped with copper bars and screws
both sides to a copper heat sink .looks great.
One guy made his own Al heatsink from folded Al strips and on top of it had a
copper heat spreader
Baruch Zilbershatz
Nitzanay-Oz 118
Nitzanay -Oz
42836
ISRAEL
phone: (+)972-052 8753838
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Paul Decker
Sent: Sunday, October 17, 2010 12:20 AM
To: amps@contesting.com
Subject: Re: [Amps] New 2 PA design
Hi Dan,
You are right, heat and control are the primary issues to solve, and they can
be solved in a solid state design just as they are in a tube design.
When the QEX article came out, I contacted JA1DJW about reproducing his
article. He was very kind and sent me many emails with details, pictures and
some of the critical parts for the amp. I think there are two fundamental
reasons the 2.5k isn't rated for full power output in continuous mode.
The first reason is the power supply isn't rated for continuous duty and is
maybe a bit under sized for the application. A secondary reason would be the
heat issue. Nobuik sent me a heat spreader but I opted not to use it since the
heat spreader is about 3.5" x 3.5" x 3/8" copper. I opted to use a 12 " x 8"
x 1/2" heat spreader with "copper fins" attached and replicated his machine
work layout onto it. Efficiency is more along the order of 60% at the worst,
usually better though.
Paul, kg7hf
From: Dan Levin <dan@andlev.com>
Subject: Re: [Amps] New 2 PA design
The big issue with parts like the ARF-1500 is managing the heat. For
high duty cycle use, like contesting or RTTY (or worse yet, contest
RTTY :-) ), you are dealing with dissipating something like 1500 watts
of heat (assuming 50% efficiency running class AB) being generated in
an area about one inch by three inches.
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