Topband: [Bulk] Re: RG-6 questions

[Jim Brown]

On Mon,3/16/2015 10:52 AM, Mike Waters wrote:
> The Commscope flooded quad-shield RG-6 I bought was was significantly less
> than 10 cents a foot, and that included shipping! For two 1000' rolls, two
> different sellers, months apart.

Right. But it doesn't have two 97% copper braid shields. Remember that 
coax loss is I squared R below 500 MHz, so what matters is conductor 
resistance at the frequency of interest. As Tom has noted, you can't 
tell much from RG-numbers, few modern cables conform to their original 
MIL specs. Rather, you must study the data sheet, if you can find one.

Belden is better than average at that, but note that the precision of 
their loss specs is a tenth of a dB in 100 ft, and few CCS cables have 
loss specified below 10 MHz. That means, for example, that a loss spec 
of 0.1 could be anything between 0.05 and ).149; 0.2 between 0.15 and 
0.249. If your run is only 100 ft, that's probably plenty good enough. 
But if your run is 400 ft, that means the loss is between 0.2 and 0.6 
dB, or between 0.6 and 1.0 dB. Many of us do a lot for 0.4 dB in the TX 
chain. :)

The 240 ft feedlines to my 160M sloping wires are Commscope 3227, which 
is #10 solid copper center, heavy copper braid plus foil. I've measured 
0.22 dB/100 ft at 1.8 MHz.

73, Jim K9YC