On 7/7/2015 3:05 AM, John S wrote:
On 7/6/2015 1:03 PM, wrote:
John S wrote:
On 7/6/2015 11:01 AM, Jerry Stuckle wrote:
On 7/6/2015 4:20 AM, Ian Jackson wrote:
In message , rickman
writes



How about we quit with the speculation and come up with some numbers?

Here is a simulation of a 50 ohm load with a 50 ohm matched series
output impedance and a voltage source of 200 VAC peak. Power into
the
load is 100 W.

http://arius.com/sims/Matched%20Load%20Power.png

Same exact circuit with the series impedance of just 1 ohm, power
into
the load is 385 W.

http://arius.com/sims/UnMatched%20Load%20Power.png

I'd say that is pretty clear evidence that matched loads are not the
way to maximize power transfer when the load impedance is fixed and
the output impedance is controllable.

Quite simply, if your prime objective is to get maximum power out of a
power (energy?) source, the source having an internal resistance is a
BAD THING. You don't design the source to have an internal resistance
equal to its intended load resistance. No one designs lead-acid
batteries that way (do they?), so why RF transmitters?

While theoretically you can extract the maximum power available
from the
source when the load resistance equals the source resistance, you can
only do so provided that the heat you generate in the source does not
cause the source to malfunction (in the worst case, blow up).

Because DC power transfer is not the same as AC power transfer.


Why not? Does something happen to the laws of physics with AC?

Yes, quite a lot, you get a whole new set of laws.

If you apply 1vDC to a 1 ohm resistor, you get 1A of current. If you
apply 1vAC RMS (at any frequency) to a 1 ohm resistor, you get 1A of
current. How does the AC change the law?


You apply 1vdc to a 0.159 microfarad capacitor and you get 0 amps
flowing (open circuit).
You apply 1vac at 1MHz to that same capacitor and you get 1 amp flowing,
with the current leading the voltage by 90 degrees.

You apply 1vdc to a 0.159 microhenry inductor and you get infinite amps
flowing (short circuit).
You apply 1vdc at 1MHz to that same inductor, and you get 1 amp flowing
with the voltage leading the current by 90 degrees.

You place the capacitor and inductor in series.
Fed with DC, you get 0 amps flowing (open circuit).
Fed with 1MHz AC, you get infinite current flowing (short circuit).

You place the capacitor and inductor in parallel.
Fed with DC, you get infinite current flowing (short circuit).
Fed with 1MHz AC you get 0 amps flowing (open circuit).

There is a huge difference between ac and dc!

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================