On 10/17/2010 2:26 AM, Baruch Zilbershatz wrote:
> Thank you for correction.
> In Hebrew it is very easy...
From the address I sorta thought that might be likely. <:-))
It's difficult for the brits and us to communicate and we have the same
basic language.
Then there are those languages that use a different syntax, or order and
words whose meanings depend on how they are used.
73
Roger (K8RI)
> 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 Roger (K8RI)
> Sent: Sunday, October 17, 2010 8:21 AM
> To: amps@contesting.com
> Subject: Re: [Amps] New 2 PA design
>
>
>
> On 10/17/2010 1:37 AM, Baruch Zilbershatz wrote:
>> 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.
>
> I hope you mean "on top of it" as meaning "in addition to". Copper, the
> better heat transfer material goes *under* the finned aluminum heat sink.
> Putting the Aluminum first is like installing a resistor as it would
> limit the ability to transfer heat.
>
> Actually this is an ideal place for water cooling and it doesn't take
> much. In addition you can even use chilled water.
> The heat sink is at ground potential so the problems associated with
> water cooled vacuum tubes running high voltage are not encountered.
>
> The best heatsink compound goes between the transistor and copper heat
> sink. Using an all copper heat sink makes more sense than using a
> sandwich of copper and then finned aluminum except to save money and
> when you get into a project with expensive transistors, the cooling
> system is certainly not a place to try to save money. It's a place to
> save expensive transistors. Of course if copper is difficult to obtain
> in the required dimensions I can understand using a finned aluminum heat
> sink over the copper. This might even be a good place to use the
> multiple "heat pipes" in an exotic configuration.
>
> 73
>
> Roger (K8RI)
>> 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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