True, the loss is related to conductor resistance. But, in a given size 50
ohm cable, such as the .405" diameter sizes, RG213, LMR400, 9913 etc., the
dielectric constant dictates the center conductor size.
The low density foam dielectrics require a much larger center conductor to
maintain a 50 ohm impedance and the lower losses are a result.
So, indirectly the dielectric does contribute to the loss in a given size
cable.
I agree, 7/8" Heliax type cable is wonderful stuff. There must be millions
of feet in surplus these days.
73,
Gerald K5GW
In a message dated 2/17/2015 8:38:06 P.M. Central Standard Time,
jim@audiosystemsgroup.com writes:
On Tue,2/17/2015 1:30 PM, Ed Sawyer wrote:
> I can tell you one reason to spec RG213 over LMR400 to feed your Mosley
> tribander, or any other tribander for that matter.
There are some misconceptions here that are the result of advertising.
Loss below about 500 MHz is entirely due to the resistance of the
conductors at the frequency of interest. The dielectric does not
contribute to loss below that frequency unless it's wet, and if it's
been wet, the braid is probably degraded, increasing copper loss. :)
If you really want low loss, use hard line. I'm feeding my SteppIR with
350 ft of 7/8-in. :)
73, Jim K9YC
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