[Amps] New 2 PA design

[Paul Decker]

The DL amp does look good.   The 2.5k has the same type of bars and screw clamps as well.  I used the same ones as well. 



Paul 


----- Original Message ----- 
From: "Baruch Zilbershatz" <4z4rb at bezeqint.net> 
To: "Paul Decker" <kg7hf at comcast.net> 
Cc: Amps at contesting.com 
Sent: Sunday, October 17, 2010 1:37:41 AM 
Subject: RE: [Amps] New 2 PA design 

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 at contesting.com [mailto:amps-bounces at contesting.com] On Behalf Of Paul Decker 
Sent: Sunday, October 17, 2010 12:20 AM 
To: amps at 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 at 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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