Ted Bruce wrote:
Roy,
What wiould be the property of a polymer like acrilic or polycarbonate
to determine its effectiveness as an insulator or a dielectric?
Volume resistivity?

Tnx,
Ted KX4OM

Volume resistivity is a useful measure only at DC.

To determine a dielectric's lossiness at RF, look at the loss tangent,
dissipation factor, or power factor. Loss tangent and dissipation factor
are the same thing, and when loss is low, power factor is also the same
for practical purposes. You'll find these in tables and descriptions of
the electrical properties of insulators. Some searching will usually
turn them up on the web if you don't have access to the appropriate
reference books. Note that the loss properties are usually a function of
frequency, so use the value at approximately the frequency of interest.

In some situations, the capacitance of the dielectric can be important,
such as when you're using it as a coil form or antenna covering. For
that, look at the dielectric constant or relative permittivity (which
are the same thing). This also changes somewhat with frequency.

Roy Lewallen, W7EL