On Wed, 7 Jan 2004 11:43:17 -0500, "Craig Buck" wrote:

I understand matching at
the transmitter end. I understand using low loss line. I don't understand
why the mismatch at the antenna junction is ignored.

Hi Craig,

Because the match performs a complete reflection without Rloss and the
antenna performs a less than complete reflection with Rr. At least in
theory. The Rr eventually claims all the power. If you wish, this
could be thought of a dampened ringing to every cycle of transmission.
If you compare the length of the storage component, the transmission
line, to the Wavelength; then such a dampened wave diminishes to
inconsequence within microseconds. Your ear (or your contact rather)
will never witness the blur of data unless your transmission line is
several milliseconds long (and its loss will certainly snub the effect
which still means no one will ever hear it).

Leaving the purity of theory behind, the match is not without Rloss as
every physical component exhibits some value even if immeasurable by
common instrumentation. Its comparison to the Rr of the antenna,
again, bears on efficiency.

This scenario of the match interface to antenna interface is akin to
the resonant cavity of the Laser whose light bounces between two
mirrors, one perfect, the other partially transmitting, but always
with a significant emission. Your speculated SWR of 200 only
amplifies the loss of the system and is not typically encountered AND
ignored.

A typical SWR of 1.2 or 1.5 or 2 or 3 or 5 could be ignored with
impunity, but the scale of loss is in the ohmic resistance of the
system components. The hazard of high SWR is more to the source and
components (arc over or melt down). If you had a 5 Ohm Rr antenna
with a 45 Ohms of ohmic resistance, the evident SWR of 1:1 would not
guarantee an efficient solution. More folks pay attention to THAT
than a 2:1 for a 25/100 Ohm Rr.

73's
Richard Clark, KB7QHC