[TenTec] [SMC] OT: Half inch Andrews Heliax LDF4-50A vs LMR-400

[Jim Brown]

On 4/26/2013 11:11 AM, Carl Moreschi wrote:
> Jim, if this were true the loss for RG8 for 28 mhz would be the same 
> as 14 mhz.  But they are not the same.  28 mhz is about twice the loss 
> as 14 mhz.
>
> What am I missing here?

Skin effect.  The resistance in the equation is the resistance at the 
frequency of interest, which  is a multiple of the DC resistance, and 
follows well known equations.  The primary factor causing bigger coax to 
have less loss is the o.d. of the shield. The larger diameter center 
also helps. We LOOK for coax with low DCR, because that combines with 
skin effect to determine the resistance at the frequency of interest.

73, Jim K9YC