Hi Again:
Two more things I would like to comment on:
Some people have made the statement that reflected power eventually
gets radiated (with the exception of cable loss) because the power
goes back and forth in the cable.
This is incorrect.
The forward travelling power arrives at the antenna where some is
delivered to the antenna and some is reflected. The reflection is
created because the antenna is a mismatch (VSWR > 1:1) at the end of
the cable.
Consider the reflected power. It too is travelling down the cable but
towards the transmitter. The transmitter is connected to the cable
so, to the reflected wave, it is a load at the end of the cable. This
reflected wave will only be sent back towards the antenna if the
transmitter impedance has a VSWR much much greater than 1:1. Most
transmitters are quite good and should have a low VSWR, therefore,
most of the reflected wave from the antenna will be delivered to the
transmitter where it will be dissipated. Transmitters get hot!
On a different subject: Tuners.
Tuners do nothing more than fool the transmitter into thinking it is
looking at a matched cable. If you connect a tuner at the input to
your cable and "tune out the reflections" you will have a low VSWR
between the transmitter and tuner and the SAME high VSWR between the
tuner and the antenna. Tuners dissipate or cancel out the reflection
from the antenna so that it does not reach the transmitter. Tuners
get hot too. You do not radiate more power, unless you allow the
transmitter to output more power because it does not see the
reflections. Sometime when you are up and running, put your power
meter between the transmitter and tuner and then between the tuner and
antenna - see what you read. Make sure the antenna has a high enough
VSWR so that you see reflected power.
73
Steve Best
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