Chris

./atten.pl -8
driver Z: [8.00] ohms
Series resistor: [4.82] ohms
Parallel resistor: [5.29] ohms

#!/usr/bin/perl -w

if ( ! @ARGV ) {
$drop = -6; # dB
}
else {
$drop = shift(@ARGV);
}

$driver_Z = 8; # ohms

# split the load between the driver and the resistor
$Rp = (10 ** ($drop / 20 )) * ($driver_Z/(1 - (10 ** ($drop / 20 ))));

# calc the the combined impeadance of driver and parallel
# resistor, and subtract from original Z.

$Rs = $driver_Z - ( 1 / ( ( 1/$Rp ) + (1/$driver_Z )));

printf(" driver Z: [%3.2f] ohms\n Series resistor: [%3.2f] ohms\n Parallel resistor: [%3.2f] ohms\n",$driver_Z,$Rs,$Rp);