AVR-Chat

> ... An antenna tuned for 450 MHz won't be resonant on 900 MHz...

Probably true.  But - verging on OT here - there is nothing magic about 
antenna resonance.

An antenna is an impedance-matching transformer; the secondary load is 
space.  When an antenna matches the typical 50-ohm transmission line to 
the ~400-ohm impedance of space, power is transferred and the antenna 
will radiate.  Some antenna designs will do that at multiple 
frequencies; simple dipoles (the driver element in a Yagi is usually a 
dipole or folded dipole), for example, will behave similarly on the 
fundamental tuned frequency and the _third_ harmonic - but not the 
second - I think you'll find.

The complex Yagi antenna, with multiple director and reflector elements, 
though, will probably will not work well at any frequency but the one it 
is designed and tuned to.


Tom