"Hal Rosser" bravely wrote to "All" (04 Apr 05 20:48:04)
--- on the heady topic of "VF, low-loss line, high-impedence line - =
relationship"

HR Reply-To: "Hal Rosser"
HR Xref: aeinews rec.radio.amateur.antenna:27947

HR I've noticed, (but have not studied), some loose relationships in
HR transmission line characteristics (and I guess waveguides fit in
HR here). From an observer's point of view, it seems that a high
HR characteristic impedence line (like 400-ohm or 600-ohm ladder line)
HR also is usually a lower-loss line, and has a higher velocity factor.
HR It also seems that some coax may have a low VF and high loss.

HR Is there a real cause for the relationship of these 3 characteristics
HR of transmission lines ? Is it something we can generalize ?
HR It makes some sense to say that the faster a signal gets through the
HR line, the less loss it will have - and that gives some credence to the
HR relationship in VF and loss being inversely associated.

You are right there is a connection between wire diameter and spacing.
It has to do with the self inductance and resistive losses of two
conductors in proximity. By contrast a balanced line has a wider
spacing and also allows part of the energy to travel unhindered, so to
speak. It helps if the balanced line is designed to be close to the
theoretical impedance of free space. The price to pay is that it is
more susceptible to the environment. The loss in coax is a trade off
to achieve stability.

A*s*i*m*o*v

.... "Beware of all enterprises that require new clothes." -- THOREAU