[amsat-bb] Re: LMR 400

[Nate Duehr]

On Aug 19, 2008, at 7:09 PM, James - KB7TBT wrote:

> 400-Series Coaxial Bulk Cable- Available by the Foot or Reel
>
> http://www.hyperlinktech.com/productfamily.aspx?id=249


I recognize the CommScope brand name in this website, and know that  
lots of commercial folks use their hardline... but the other  
manufacturer I don't recognize.

"True" LMR-400 is only made by Times-Microwave.  There are a lot of  
"copy-cats" on the market now, but little engineering data on whether  
or not it performs to rated specifications.

Has anyone on the list tested any of this "400-series" type cable from  
either of these two manufacturers to see if it lives up to real  
LMR-400 specs?

I hate to say it, but I've been burned enough times by the old adage,  
"You get what you pay for" that I'm leery of these LMR-400 "series"  
copies.

LMR-400 has also been traced to PIM (passive intermod) problems on  
many commercial sites when used in feeding repeaters, due to the "foil  
over braid" design, and many repeater owner/operators won't use it  
anymore.  (Every little "bump" in the braid touching the foil is  
another tiny little junction where diode-behavior can create IM mixes.)

Still good specifications for simplex services like satellite, no  
doubt -- but just mentioning that it does have some limitations/ 
downfalls in duplex service on FM repeaters.

--
Nate Duehr, WY0X
nate at natetech.com