Richard Harrison wrote:
The newly minted RF and the twice reflected RF are similar, both having
their volts and amps in-phase. So, the similar RF constituents merge to
have a go at the reflection point.

Wonder why we have protection circuitry in transmitters?
The superposed forward voltage and reflected voltage can damage an
unprotected transmitter. The superposed forward current and reflected
current can cause over heating in an unprotected transmitter.

The transmitter sees whatever impedance it sees and that impedance
can be highly reactive. The superposed voltage can be high or low.
The superposed current can be high or low. The phase between the
superposed voltage and superposed current can have lots of values.

Just a for instance - assume the transmitter is putting out 70.7v
in phase with 1.4a at zero deg. The arriving reflected wave is 50v
at 90 deg and 1.0a at -90 deg. The load seen by the transmitter is
86.6v at 35 deg and 1.72a at -35 deg. Over voltage and over current
exist at the transmitter output. The forward power is 100w and the
reflected power is 50w. The net power being delivered to the reactive
"load" seen by the transmitter is 86.6*1.72*cos(70.4) = 50w.

The math model is trying to dictate reality. It is supposed to be
exactly the opposite. There is no magic barrier that automatically
rejects reflected energy from a transmitter. Reflected energy
arriving at the transmitter can drastically alter the impedance
away from the designed-for load impedance. The transmitter sees
one of the transformed impedances that exists on the SWR circle.

Note that the problem disappears in a matched system where reflected
energy is not allowed to reach the transmitter.
--
73, Cecil http://www.qsl.net/w5dxp


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----