Ian Jackson wrote:
In message , dave



No. What do you mean by "match"?

The tuner/matcher transforms whatever impedance that is connected to its
'output' to 50 ohms resistive at its 'input'. That way, a transmitter
feeds into a 50 ohm load - which is normally what it will be designed to
feed into.

When receiving, the same applies (although, of course, the signal is
passing through the tuner/matcher from the opposite direction). Its
'input' on transmit is its 'output' on receive, so the output (which
feeds the receiver) is 50 ohms - which is what most communications
receivers are designed to be fed from. In practice, if purely receiving,
you will normally simply twiddle the tuner/matcher for strongest signal
on the receiver (ie maximum smoke). It doesn't really matter too much
whether or not you actually achieve 50 ohms at the matcher 'output' port.

Or have I got things wrong?

You are describing a "transmatch" when used between the generator and
the transmission line. This prevents the VSWR from frying the
transmitter. It does nothing to make the antenna work any better. The
transmitter can feed 50 Ohm co-ax directly. A tuner at the far end of
the transmission line will improve radiation while matching the load to
the transmission line and back to the transmitter. The radiation
improvement may be negligible or more dramatic, depending on the type of
antenna. When receiving you don't worry about frying the transistors
(unless you have a 2001D/2010!) so you just want to make sure you don't
break the hose rule (NO Higher Z generator into Lower Z load). That is
why a 9:1 transformer works OK for receiving. If you transmit through it
the transmitter will see close to a short circuit if the antenna is
resonant.