[TowerTalk] L-Com 400 coax

[Jim Brown]

On Wed, 20 Jan 2010 21:33:14 -0800, Greg wrote:

>I can get a 1Kft roll locally for $300.  I know that's only $70 
less 
>than ordering online but I don't have to mess with shipping either.

>But I have not been able to find any reviews on this stuff.

Ask for specs and a manufacturer's part number.  

Coax loss at HF is entirely due to copper loss. Dielectric loss 
doesn't kick in until you hit UHF (unless the dielectric is wet or 
otherwise defective). For lowest loss at HF, look at the DC 
resistance of the center conductor and the shield. The lowest loss 
cables are about 2.3 ohms/1,000 ft. BTW -- don't believe the 
advertised loss specs of the LMR cables -- I recently measured 
LMR240 and found their advertised loss numbers to be quite 
"optimistic," and only slightly better than Belden 9258 or CQ118, 
the equivalent cable that The Wireman sells.  

I have bought Commscope 3227 real cheap, which came onto the surplus 
market as the result of a telecom bankruptcy. It's VERY good cable, 
very low loss, and standard PL259s fit it quite well. It's 2.3 
ohms/ft total DCR. 

Yes, resistance is increased by skin effect, but guess what? The 
laws of physics work the same way for all of these cables, and skin 
effect simply multiplies all of their resistances by the same factor 
at any given frequency. So for all practical purposes, we can 
compare the HF loss of cables by comparing their total DCR. 

73,

Jim Brown K9YC