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Old September 23rd 04, 01:46 AM
 
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Reg,
Can this be conscrewed as a combination loop/.dipole?
It would appear that you can place the L/C circuit at the center of the
dipole and fed either with a delta match or a capacitive /inductive coupled
dipole for impedance purposes. Could not quite fathom from your notes what
it was exactly. I made a 160M rotatable dipole last winter based on the
above and used the radio auto tuner control to change the values on the L/C
circuit to move up and down the band because of the resulting narrow
bandwidth at any set frequency or band.
Art

"Reg Edwards" wrote in message
...
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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