Roger Hayter wrote:
wrote:

Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

As we all agree, under equal output impedance and load impedance
conditions, onty half the RF generated reaches the load. This is sim;ly
not acceptable or likely for any real-world transmitter. Do 50kW radio
station output valves dissipate 50kW? I hope not!

You are attempting to mix circuit theory and transmission line theory.


You rather have to if you are going to connect a practical circuit to a
practical transmission line!

Nope.

In the real world you pick a system impedance to match the transmission
line you want to use.

You design the transmitter with circuit theory to match the line.

You design the antenna with electromagetic theory to also match the line.

The "valves" in a transmitter are not connected to the transmission
line. The "valves" in a transmitter are a voltage source connected
to an impedance matching network which then connects to a transmission
line.

Fair enough. Do you want to dissipate 50kW in the matching circuit

What anyone wants is irrelevant to physics.

A 50kW radio station does not generate 50kW of power, it generates
a voltage that results in 50kW being dissipted into a 50 Ohm load.

There is a difference.

Not much, seeing it also has to supply the in-phase current to maintain
that voltage across the resistive 50 ohm load.

The phase of a transmitter is what it is and this is a red herring.


--
Jim Pennino