Remember that the amount of insulation to wire ratio increases the loss
of a transmission line. Thus, coax being dense insulation has higher
loss than ladder line, with sparse plastic. The loss tangent of the
rubber or plastic dielectric material is the penalty you have to be
concerned about.
Zip cord is closer to 102 ohms Impedance, for many types. It is
believed here that the ARRL loss factors for zip cords were for colored
PVC or even colored Rubber types. Colorant may increase losses,
depending on its metal derivation, or carbon derivation. Zip cord
spacings and wire diameters vary widely for various types. Clear
speaker cable might make a good zip cord antenna material, rather than
the rubber zip cords.
Ten Tec content: Black cased Ten Tec radios need to be protected from
direct sun exposure at Field Day, or they could overheat. Same for any
dark radio case. Once we had a tuner, (Tokyo High Power) that detuned
itself by mid afternoon at Field Day. Placing a hand on the dark case
told me it had sat in the sun. Retuning was successful. Apparently,
the coil turns spacing changed as the tuner heated up.
Stuart
K5KVH
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