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Coax question - are the "generic" versions of LMR-400 and LMR-400 Ultraflex as good as the "name brand" or is it not worth the savings?
On 09 Mar 2013 10:33:58 GMT, Rob wrote:
Jef wrote: First look at the center conductor. The larger the beter as that is where most of the loss is. Solid wire will have slightly less loss, but if used with a rotator, it can flex enough to break over the years. Then look at the shield, especially the braid. It should be around 95% or beter. This is where the next loss is. Most of the low loss coax has a foil type shield plus 95% or beter braid. That applies for under 1000 Mhz anyway. Look at the velocity factor. The low loss will normally be .80 or higher. Just to point out that the diameter of the centre conductor is fixed by the impedance of the coax, the outer diameter, and the dielectric constant of the insulator. So for a cable that will fit in a PL259 or N type it means that you will only have a very limited choice or inner diameters that are dependant on the dielectric used, and that dielectric is likely to have just as significant effect on loss as the diameter of the inner, more as the frequency goes up. However, lower loss insulators generally have a lower dielectric constant which also mean a larger diameter inner, for a fixed outer diameter. Jeff Also, it needs to be pointed out that the original poster asked about differences in make of coax, while the discussion now focuses mainly on type of coax. Of course, that is a different topic. There are differences between types of coax (solid center vs stranded, solid dielectrum vs foam or air or helix or bamboo etc, foil shield vs braid or both), but what the OP asked is if an LMR-400 from one manufacturer is equal to an LMR-400 from another manufacturer. In that case, the diameters, insulation types, braid types etc should be the same and it is only thw manufacturing quality that would be different. However, always check. There always are manufacturers that try to get away with using less copper in the braid, for example. Copper is expensive these days. Thanks to you, Ralph, and Jeff for your kind responses and some great information - just what I needed. I've a little more research to do, but I got the answers I was looking for, and more. I really appreciate it. This is a great group. 73, Bob KB2ZGN |
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