DJ7WW wrote:
>Barry's designs use a loading coil in each leg rather than a trap, and
>the coils are roughly at the point where the insulator would be for a
>half wave on the higher band. Then the coils, and a bit more wire. The
>160/80 version is roughly 160 ft long, the 80/40 version is a bit under
>100 ft.
>It will not work on two bands without a trap
>
>73
>Peter
>
Yes, it will. The point you are missing is that the mode of resonance
changes between the two bands.
On the lower band, the mode of resonance is a conventional shortened
half-wave; the current has the same phase along the whole length of the
wire. But on the higher band, the coil creates a different "1.5
wavelength" resonance mode which includes a phase reversal.
The change of mode is what makes the dual resonance possible.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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