[AMRadio] power ratings


Donald Chester k4kyv at hotmail.com
Tue Jul 12 14:28:48 EDT 2005


>The plate dissipation of the 6146's is the key. Your carrier steady on
>should not exceed the dissipation rating. This is about 50 watts if I
>remember right which would give you 200 watts PEP. So your power suppl;y
>should be capable of about 150 watts continuous and it will handle the 200
>watts on peaks. I would beef up the fan so that I had a good amount of air
>passing the glass of the 6146's to keep the seals cool.

In AM linear service, the carrier output should not exceed HALF the total 
plate dissipation.  A 6146 runs about 25 watts plate dissipation, so with a 
pair of them, you should be able to  run 25 watts out.  With 100% modulation 
in the positive direction, that would be 100 watts pep.

A properly functioning AM final capable of 100% modulation should run about 
33% carrier efficiency.  That means that two-thirds of the input power is 
dissipated in the plates of the final, and one third is delivered as rf 
output.

When the carrier is modulated, the final actually  becomes more efficient, 
so the plate dissipation is reduced under modulated conditions.  The DC 
input should not vary, so that simply means that some of the DC input that 
was being dissipated as heat is now being converted to rf output in the form 
of sideband power.





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