[AMRadio] AM power

[Geoff Edmonson]

On 06/19/2011 07:56 PM, Gary Schafer wrote:
>
> Hi Geoff,
>
> You are the one telling me I am wrong. :>)
> I was just showing a different angle on the same thing but I think that you
> interpreted it differently.

Well, let's see if we can agree on something, ok?

My voice has an SR of 4.  I use a Sure 55-S mic (balanced line out) into 
a 31-band graphic EQ (balanced line in) to a Modified Bogen PA (added 
20db or so of inverse feedback).  The output of the Bogen comes off the 
plates of the output tubes to the WA5BXO designed solid-state audio 
drive, capable of ~600v-pk audio swing on the grids.  Basically, 
whatever audio is on the plates of the output tubes in the speech amp, 
is directly applied to the grids of the 250TH's.  the modulation 
transformer is out of a T-368 and there's 60HY @ 500mA of inductor 
shunting the DC off of the secondary of the modulation transformer.

With my SR of 4, in order to keep the negative peaks close to 100% and 
maintain 1500w PEP, I can not run my output power to more than about 
90~95w.  We agree on that, right?

If I ran the carrier level up to twice that, I'd have to reduce the 
positive peaks by a factor of 4, to stay around ~1500w PEP, but where 
are the negative peaks?  ALSO reduced by a factor of 4, and therefore I 
would sound like I'm 25% modulated, an I'm only running now ~200w of 
carrier out.

So, what I do to run a little more carrier, is reduce the voltage on the 
250TH's so the positive peaks are not as high, and run the carrier up to 
~175.  I still get an SR of 3, even with half the B+ on the modulators, 
but the negative peaks are close to the baseline this way, as well.

That's how things are in -my- world.

73 = Best Regards,
-Geoff/W5OMR