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Re: [Amps] Alpha vs Henry

Subject: Re: [Amps] Alpha vs Henry
From: Jim Barber <audioguy@q.com>
Reply-to: audioguy@q.com
Date: Wed, 06 Apr 2011 15:33:42 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Interesting side-thread. I've been thinking about replacing my 
black-faced Alpha 77 with an AL-1500, primarily because the Alpha 
doesn't have 160 and I don't like the nature of the "upgrade" to put it 
in. (My "yellow-faced" PA77 has the 160 mod but I'm afraid to run RTTY 
or even full-power AM because I'm paranoid about the toroids)

73,
Jim N7CXI

On 4/6/2011 3:22 PM, Roger (sub1) wrote:
> On 4/6/2011 5:05 PM, Al Kozakiewicz wrote:
>> Can anyone tell me how much power an AL-1500 is rated to produce at a 100% 
>> duty cycle?
>>
>> During RTTY contests and outputting about 1000 watts, the tube side of the 
>> cabinet gets mighty warm.
>
> It should.  Running 100% duty cycle and 1500 watts out at 60% efficiency
> means you are dissipating 1000 watts.  That is a LOT of heat. The temp
> of the exhaust air depends on how much air (CFM @ however many inches of
> H20) the fan can push.  The 8877 is a relatively small tube for its
> ratings, but it has a fairly efficient radiator.  OTOH that means a
> blower that can produce a fair amount of back pressure is required to
> get full output from the tube.
>
> As a comparison, when I had an all electric house I heated the basement
> and ham shack with 4400 watt space heaters mounted in the walls.  In the
> dead of winter it only took a few minutes to heat the 13 X 21' den to
> about 70 degrees. After that the heater would only kick on a few times
> for only a few minutes per hour. That means your amp running under these
> conditions puts out enough heat to require opening the den door to keep
> a reasonable temp.  IOW you could heat a good sized room with that amp
> on RTTY.
>
>> The power supply side seems cool - but then, that's with the cover on.  I 
>> don't know how hot is too hot and it would be useful to know at least how 
>> much continuous power the supply is rated for.
>
> If you were running large glass tubes that depend on radiation that
> cabinet would be too hot to touch.
>
> 73
>
> Roger (K8RI)
>
>> Tube cooling is probably another issue...
>>
>> Al
>> AB2ZY
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>
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