On 11/14/19 6:26 PM, jimlux wrote:
On 11/14/19 6:08 PM, Robert Harmon wrote:
Interesting stuff. I got on the Trilogy website, they have a
corrugated copper outer conductor too. Can't
find loss specs for lower HF freqs. Also suppliers and cost.
For HF, the loss is dominated by the skin effect in the shield and
center conductor - especially for hardline, which has almost no
dielectric. So the loss will go as sqrt(f). If the loss is, say,
10dB/ft at 10 MHz it will be 3.2 dB/ft at 1 MHz.
More details here:
https://www.microwaves101.com/encyclopedias/coax-loss-calculations
One thing to watch out for - if either shield or center conductor is
plated, or small enough that it's not "many" skin depths thick, then it
gets more complex.
However, our trusty friend RG-8 has an AWG 13 center conductor which is
some 72 mils in diameter, and skin depth at 1 MHz in copper is 2.5 mils.
You can get bit on cable TV coax which sometimes has a very, very thin
layer of copper on a steel core. At 100 MHz, skin depth is 0.25 mil, and
it gets smaller as you go higher.
Magnetic materials under the conductor are a particular evil. (steel
cores, nickle plate under a gold flash..)
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