On 9/20/2022 10:10 AM, Grant Saviers wrote:
The dielectric loading of insulation makes the wire electrically longer
for RF. EZNEC can model it, if you know the dielectric constant
(usually around 3 for PVC, nylon) and thickness.
The height of the dipole has a larger effect. Plus for 160 & 80 quality
copperweld is needed with thick copper, so the internal field (skin
depth) is in the copper, not in the steel which will cause high losses.
EZNEC can also model the effect of height if you know what your soil is
like. It correctly predicted a good match to 75 ohm coax for an antenna
at about 40 ft over lousy soil for a CQP setup we did, and it comes
pretty close to measurements (~ 85 ohms) for my very high dipoles over
lousy soil.
73, Jim K9YC
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