"Reg Edwards" wrote
Use program NOTATRAP. The parallel tuned circuit is not a trap at
either of the operating frequencies. Its resonant frequency lies in
between the two operating frequencies. The two operating frequencies
do not necessarily have to be harmonically related.
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Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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There is a small advantage. The whole length of the antenna is used
at both frequencies. Furthermore, the antenna can be used multi-band
at frequencies higher than the lowest design frequency. Including the
frequency at which the trap is resonant if it lies in an amateur band.

But there will be some peculiar drive-point impedances presented to
the transmission line plus tuner. For multiband use one might just as
well remove the trap which is not a trap and use the antenna simply as
a random length wire.
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Reg