Hi Tom,
I disagree that LMR400 "handles a lot more power" than RG213/U. It may
handle a bit more, under well-matched conditions, for the same reason that
it has less loss: That being, it has a larger-diameter center conductor
which obviously has less resistance and can thus handle more current.
(RG-213/U is #13AWG center conductor; LMR400 is #10AWG.)
However, because LMR400 uses injected foam poly dielectric, it has a LOWER,
not higher, dielectric breakdown voltage rating, and also has a lower
maximum operating temperature rating than RG213. Thus, under high temp or
high altitude environmentals, or under mismatch conditions where voltages
will be higher than in matched conditions, LMR400, or any "foam" dielectric
cable, is likely to fail faster.
The lower attenuation, for the same cable diameter, comes from the larger
gauge center conductor having lower skin resistance. The diameter can be
larger because the dielectric constant of the dielectric insulation material
used is lower, so to create the same nominal impedance the ratio of D/d can
be increased.
WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: n4kg@juno.com [SMTP:n4kg@juno.com]
> Sent: Thursday, October 17, 2002 11:59 AM
> To: TOWERTALK@contesting.com
> Subject: Re: [Towertalk] Coax recommendations
>
> On Wed, 16 Oct 2002 Jon Ogden <na9d@speakeasy.net> writes:
>
> SNIP
>
> > LMR400 falls in to the RG8 size classification and so uses the same
> > connectors. No problem. No issue with sealing. It's a solid
> > dielectric unlike 9913. It is suitable for direct burial. No problem
> there.
>
> >LMR400 also handles a lot more power than RG-8 and has a lot less
> > loss than RG-213.
>
> SNIP
> >
> > Jon NA9D
> >
>
> How much more power does LMR400 handle than RG213?
>
> How much less loss than RG213?
>
> How does it achieve these interesting results in the same
> size cable?
>
> Tom N4KG
>
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