[AMRadio] AM Amps


Geoff w5omr at w5omr.shacknet.nu
Tue Jan 11 11:31:08 EST 2005


Gary Blau wrote:

> Not sure where the article is exactly pertinent to this.
> If the exciter B+ is reduced, so is the max available exciter PEP.
> If the B+ stays the same and the screen V is reduced the max available
> exciter PEP is (roughly) the same, but the carrier power out (no mod)
> goes down.

I'll be the first one to admit that I'm 'weak' when it comes to 
pentode/tetrode design/operation.  I like triodes.  Their easier 
to work with, and require fewer power supplies.  Less can go wrong.

> If your concern is running as much carrier power as possible while
> staying within the (stupid) 1500W PEP limit then reduce your positive
> modulation as much as you can tolerate while keeping the negative
> modulation as consistently high as possible.  Won't sound very good, but
> there it is.

Why wouldn't it sound as good?  You've just reversed the 'phase' 
of the audio if you, say, switch the grid caps on the modulators, 
or switched the plate caps on the modulators, even reversing the 
polarity of the microphone would have *basically* the same 
effect.  Yes, your positive peaks would reduce, and you can run 
the carrier level back up.

At 1500wPEP output (as John so eloquently described in his 
article) with his rig and voice, he would have to keep his rig at 
220w input (around 160w of carrier out) to keep within the 1500w 
limit.  Inverting the audio phase, he could probably run 1000w of 
carrier, with PEP audio to 1500w, still have the same QUALITY of 
audio, -and- probably be heard better, due to the lack of 
interference from the 160w carrier, to the 1000w carrier.
It just wouldn't sound -as loud-.

Agreed, 1500w PEP output is -stupid-.

> g
> 
> Geoff wrote:
> 
>>...I don't think that's what happens.
>>
>>http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm
>>
>>That's a great read.  Everyone -should- read that.

73 = Best Regards,
-Geoff/W5OMR




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