[AMRadio] AM Amps


Gary Schafer garyschafer at comcast.net
Tue Jan 11 22:50:18 EST 2005



Geoff wrote:
> Gary Schafer wrote:
> 
>> I know full well that there is no such thing as a 375 watt carrier 
>> limit to AM power in the FCC rules. I never said there was.
> 
> 
> Ok, good.  I was just making sure ;)  Too many people believe that 
> there's some 'magical mystification' about 375w of carrier output being 
> the 'legal limit'.
> 
>> I was trying to "clarify" Ronnie's statement about how much power he 
>> runs his 813's at when he says he runs them at legal power out.
>>
>> And since we don't know if Ronnie has a symmetrical voice pattern or 
>> otherwise, we can only assume it is symmetrical when discussing 
>> general power principles.
>> Maybe he has the peaks phased so maximum peaks are in the negative 
>> direction? I don't know. Either way it appears as though he only has 
>> enough headroom for less than 50% modulation in the positive direction.
> 
> 
> Agreed, there.  And, I've been to Ronnie's shack.  I'm pretty sure he 
> doesnt' do any audio shaping, or phasing, or any other audio tricks on 
> either the Ranger or the Globe King 500 he's running there.
> 
>> On top of that the plate dissipation is around 380 watts per tube if 
>> the amp is tuned properly, which it can't be if it is not burning up 
>> tubes.
>>
>> That is the whole point, if you are paying attention. :>)
> 
> 
> I was... it was just the 'legal limit' that caught my attention (yet 
> again ;->)
> 
>> Maybe you could tell us how much peak envelope power would be 
>> available from a pair of GG 813's at 375 watts carrier out with 100% 
>> modulation?
> 
> 
> I'm not sure you can get more than around 1kW PEP output of a pair of 
> 813's... and probably more like 800w.  (3) in parallel would be a 
> different story, though.
> 
> 73 = Best Regards,
> -Geoff/W5OMR


I would say you are pretty much on the mark there. I have a pair of 
813's in GG also. I only run them at around 2500 volt and can get about 
650 watts max out with 100 watts drive if I remember right.

I ran them well over 3000 volts many years ago and got quite a bit more 
out of them but didn't have a decent watt meter then so I don't know 
exactly.
1000 watts out seems doable but they will be running around 1600 watts 
or more input. They will turn pretty red. Even on SSB at that power.

73
Gary  K4FMX





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