[Amps] How light can you make a 500W amplifier?

Tue, 15 Oct 2002 14:14:15 -0600

>> Is this daffy????
>> 73
>> Bill wa4lav

No, and efficiency and weight can be helped further by running at higher DC
voltages using off-line buck style converters.
I have run class E cw at 46Mhz using 100V off of a buck converter for 300W
continuous in an industrial application. There are isolation issues in off
line operation and the tuning components for class-E can be a weight factor
at lower frequencies, but the sweeping statement below has some traction. Of
course, the devil is in the details. Eliminate the SSB/AM requirement and
you can get rid of quite a bit of weight. An example is found in a QST
article from a few years back by Dr. David Rutledge at CalTech. His 700W CW
7mHz class E amp used a $5.00 part, ran at up to 140VDC and weighed about
.5Kg, not including a power supply. The power supply was heavy, but this
could be alleviated with a switchmode supply.

George K. Watson
K0IW

At 02:43 PM 10/15/02 -0400, ToddRoberts2001@aol.com wrote:
><PRE>In my opinion the future for lightweight SSB amplifiers would be a
>solid-state amplifier based on EER ( Envelope Elimination and Recovery)
with
>a Switching Power Supply. An EER amplifier can use a Class-E Power amp with
a
>typical power efficiency of 90% and a Class-S switching audio amp with
>typical power efficiency of over 90%. Such high power efficiency allows use
>of a much smaller heatsink and cooler and more reliable operation of the
>final transistors. A 500 watt output amplifier @ 90% efficiency would
operate
>nicely from a power supply of about 50VDC @ 11 amps. SMPS are available
with
>power factor correction of 99% and overall efficiency of 85-90% and they
will
>operate over input voltage range from 100-240 VAC / 47-63Hz  auto-detect. A
>50VDC@11Amps SMPS would weigh about 5-6 lbs or less than 3Kg. The Class-E
>power amp and Class-S modulator could be built with a weight of about 5-6
lbs
>also, for a total weight of 6Kg for the power supply and 500 watt output
EER
>amplifier. The whole thing could be put into a table-top cabinet about the
>size of a Collins 30L-1 without much trouble and probably not weigh more
than
>7-8 Kg.  73 Todd Roberts WD4NGG .
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