Jim Brown wrote:
>>> Here's measured data for Harbor Industries RG400.
>>> These curve shapes are predicted by the wave equations and are typical of
>>> virtually all transmission lines.
As to common curve shapes, here's Figure 3.1 from the Johnson book on
transmission lines (Howard Johnson and Martin Graham, "High Speed
Signal Propagation: Advanced Black Magic", 2003):
https://postimg.org/image/tq941yzcl/
The topmost chart trace with the extra annotation is for a
transmission line etched on a PCB, the lower six traces are for
various types of coax. Note that the "loss regions" are common to all
metallic transmission lines but it may be necessary to extend the
frequency range to lower values to see them all. The regions are also
most evident when both loss and frequency are plotted on log scales.
Jim Lux wrote:
>>> So I wonder what truly horrible coax would look like
Here's a comparison for loss between RG-400 as measured by K9YC and
RG-174/U per mfg specs.
https://postimg.org/image/zefeswdzp/
The RG-174 is Belden 8216. Per the datasheet, "26 AWG stranded (7x34)
.019" bare copper-covered steel conductor, polyethylene insulation,
tinned copper braid shield (90% coverage)".
Datasheets:
http://www.wellshow.com/spec/cable/Harbour-RG400.pdf
https://catalog.belden.com/techdata/EN/8216_techdata.pdf
I couldn't find a comprehensive *Belden* datasheet for RG-400.
BTW, the Johnson and Graham book should not be confused with Walter
Johnson, "Transmission Lines And Networks", 1950. That's also a very
good book, but the transmission line model used by Zplots, TLDetails,
AutoEZ, SimSmith, and several other programs is based on the 2003
Johnson book.
Dan, AC6LA
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