[TowerTalk] Tower and antenna decisions

[Jim Lux]

On 10/26/13 11:17 PM, Jim Brown wrote:
> On 10/26/2013 10:57 PM, Grant Saviers wrote:
>> You're the audio expert, but didn't Bob Carver figure out some clever
>> variable supply voltage tricks with his big Sunfire amps?  I have two
>> and my "Signature" stereo is rated 2 to 16 ohms (1250w/ch 4 ohms) and
>> runs stone cold even when delivering big power.  No other amp I've
>> tried had the headroom needed for my B&W 801Fs to generate max
>> orchestral peaks at concert hall levels.
>>
>> So isn't what you are suggesting been done before in the audio domain?
>
> For at least four decades, solid state audio power amps have been
> contstant voltage sources with VERY low output Z (typically 0.1 ohms or
> less) , so the voltage is constant with load Z, and power out increases
> as load Z decreases (P=I squared R, or E squared /R))
>
> There are good reasons for this -- the low output Z of the amp damps
> mechanical oscillation in the loudspeaker to clean up the sound (so that
> the bass isn't "floppy."

And bringing this back to antennas. What if your amplifier had a current 
output (e.g. infinite Z). You could "force" the current into the antenna 
element you want.

In the audio world, I don't think people much care about optimum 
Thevenin power transfer, and there's no real reason why we should do so 
in the RF world, except if there's some external constraint.  There's no 
regulatory reason for hams to have an efficient amplifiers, for 
instance.  (and you could do the same with speakers, which are really a 
"current to displacement" transducer)

And in low power stages, putting pads between stages to make the system 
less sensitive to parameter variations is well known.