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December 30th 03, 11:46 PM

In article ,
(RHF) wrote:

CraigM,

1. If you look at many Transmitter Loading Coils. They are often
Bare Wire with Insulated "Spacers" that provide an Air Gap. One of
the "Features" of this 'design' is to Allow for HEAT (Power)
Dispensation.

The space between the wires does help heat dissipation but the reason
for it is to reduce parasitic capacitance. The wire size has more to do
with how much power will go through it.

2. Many Up-In-The-Air Antennas use "Loading Coils" that are simply
made of the same Insulated Wire or Bare Wire used in the Antenna.
Frequently there is a 'small' Air Gap (about one to two wire
diameters) in these Loading Coils. Sometimes when Insulated Wire is
used these Loading Coils are simply wound with NO Air Gap. But
remember, there is the Gap (Spacing) that is created by the Covering
Insulation on both sides of the inner wire.

Loading Coil Looks Like: iWiiWiiWiiWiiWiiWiiWiiWiiWiiWi "W" = Wire
(Inner) "i" = Insultation (Outer)

Any type of electrical component exhibits all the other electrical
properties. Inductors and transformers have some self-capacitance and
resistance. Capacitors have some inductance and resistance. Inductors
of any type have a tendency to have longer electrical paths than
comparable capacitors or resistors so parasitics are more of a problem.
Most of the time care must be taken to have self-resonant behavior
occur above the frequency of operation.

Keep in mind the need to have windings apart from each other in order
to reduce the parasitic capacitance between them. Air has a constant of
one and any other solid plastic insulation will have a higher constant
so placing insulated wire in contact will still create significant
capacitance. Air is the best insulator to use.

--
Telamon
Ventura, California

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