On Sun, 10 Jul 2005 21:21:34 -0400, "KC4IH"
wrote:

I need to build a 3db pad, 50 ohm, 10 watt, to reduce the drive to my 6
meter amp. I need 2 X 300 ohms and 1 X 18 Ohm resistors and thought it would
be an easy matter to find them with enough current rating to do the job but
can't find anything larger than 1 watt carbon (not film, which are somewhat
inductive ) resistors. I can find want is called non-inductive wire wound
resistors. I can't understand how a wire wound resistor can be
non-inductive. Could someone explain this?

Look up for bifilar winding.

If your exciter is reasonably clean so that you do not think about
proper termination also for the harmonics, you just need an attenuator
for a single frequency, which should simplify things a bit.

Even if a "non-inductive" resistor has some inductance at 50 MHz, it
should not be too hard to compensate for the inductance and turn the
system into a very lossy series resonant circuit, in which the
impedance is dominated by the resistance in the area around the
resonance. An other alternative would be to put a capacitor in
parallel with the resistor to form a parallel resonant circuit at 50
MHz and the actual resistance would heavily damp the resonance. If the
inductance is sufficiently low, you will end up with capacitances that
are practical (i.e. not affected too much by stray capacitances).

This kind of approach should work at a single frequency(band), but if
multiple bands are needed or if the harmonics also needs to be
correctly matched, this approach does not work.

Paul OH3LWR