On Thu, 17 Jul 2003 09:06:32 -0500, "William E. Sabin"
sabinw@mwci-news wrote:

Dilon Earl wrote:


Where does the loss occur? If you have 3 db of mismatch loss, is it
in the coax, tank circuit?


The loss in "mismatch loss" refers only to the
fact that the power delivered by the generator to
the load is less than it would be if the load
resistance were the same value as the generator
resistance, in other words if the load and
generator were "matched".

The best way to get a handle on this subject is to
draw a diagram of a generator with voltage V=10,
an internal resistance of 50 ohms, and a load
resistor of R ohms. Let R vary from 1 ohm to 100
ohms and calculate the power dissipated in the
generator resistance (50 ohms), the power in the
load resistance (R), and the total power. Plot a
graph of the three quantities. The load power goes
through a maximum when R=50 ohms.

The maximum power dissipated in the generator
resistance is 10^2/50=2 W, which occurs when R=0
ohms. The minimum power dissipated in the
generator resistance is 3.33^2/50=0.22 W which
occurs when R=100 ohms. When R=50 ohms, the load
power is 5^2/50=0.5 W (the maximum value), the
dissipation in the generator resistance is
5^2/50=0.5 W and the total power is 10^2/100=1 W.

Bill W0IYH

Bill;
Thanks, that all makes sense. Can you consider a Transmitter to
have an internal resistance like the generator that changes with the
plate and tune controls?
If I have a 100 watt transmitter and my wattmeter shows 3 watts
reflected. Is 3 watts actually being dissipated in the tank and final
PA?
Sorry to ask such simple questions. I did search through Google
on posts on this subject, just never could find the answer I was
looking for.