robert casey wrote:


= 377 ohms (approximately)


Had heard that one wants their stealth fighters to be covered with
material that has this impedance. Also heard that any such material
that can be manufactured is frequency dependent...

If you want to see proof that what you heard isn't so, go to your local
EMI test facility and ask to see their anechoic chamber. The one I use
is pretty quiet from about 200 kHz up through the microwave range. Under
the carbon-loaded foam cones are thick ferrite plates to extend the
absorption down to the lower frequencies. You can also get ferrite
loaded paint and silicone rubber, both of which have good absorption for
several decades of frequency at least. But as Richard says, they're
awfully heavy.

Roy Lewallen, W7EL