Extract from program notes.

Program Name: NOTATRAP.exe Author: R.J.Edwards G4FGQ

A TWO-BAND ANTENNA WIRE LOADED WITH AN L & C PARALLEL-TUNED CIRCUIT

The LC parallel-tuned circuit is constructed exactly like an antenna trap.
It
is located in the antenna wire and used as L or C loading at 2 other
resonant
frequencies. Parallel-tuned circuits have a reactive impedance on either
side
of resonance. On the low frequency side there is a +ve inductive reactance.
On
the high frequency side there is a -ve capacitative reactance.

The purpose of the LC loading components is to detune the antenna wire from
its natural 1/4-wave resonant frequency. When the loading circuit is
behaving
as an inductance the antenna resonant frequency is reduced. When the loading
circuit is behaving as a capacitor the antenna resonant frequency is
increased.
The pair of resonant frequencies depend on the LC ratio, on wire length, and
on the location of the LC loading circuit along the wire.

For a given loading location along the wire and a given pair of resonant
freq-
encies this program calculates the L and C loading-component values. The
pair
of frequencies lie above and below the unloaded resonant frequency of the
wire.
The LC circuit behaves as an ordinary trap at its own resonant frequency
which,
by experiment, can sometimes be arranged to fall into a third amateur band.
But
to calculate such a fortunate coincidence is beyond my elderly patience.

The program has a built in signal source which generates a wide-ranging
testing frequency which can be used to 'measure' the input impedance of the
antenna versus frequency, checking resonant frequencies and other antenna
characteristics.

Download program NOTATRAP from website below and run immediately.
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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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