Structure: LMR-400 is a 50-ohm coaxial cable that was originally made to replace lower quality coax cables such as the RG-8. The 400 represents the cable diameter. The LMR-400 actually has a diameter of 0.405 or 10.29 mm though it is classified as a 400, similar to most coaxial cables in its class such as the RG-8 types, all of which measure .400.
Low Loss: LMR-400 is distinguished from other antenna cables in the market for its low loss characteristics. It has the lowest signal-loss among its class and compared to most semi-rigid and hard-line cables. For example: LMR-400 loses 0.04 dB / ft. at 900 MHz as compared to 0.32 dB / ft. for the RG-174
Frequency Bands: LMR-400 is excellent at frequencies greater than 1Ghz as its attenuation properties are custom made for such frequencies. If you have a radio with 1.2 GHz or more, then you should find that the LMR is your best option given that your traditional RG series does not work with anything above 1 GHz.
Conductivity: The insulators are made of tinned oxygen free copper that also come with foil conductor tapes. These are bonded directly onto the insulator thus providing a double-shielded coaxial cable conductor that is effective at all times.
Double Shielding: Due to its double bonded foil, the attenuation (signal loss) is significantly lower as compared to single shielded coaxial cables: RF shielding of LMR-400 is > 90 db as compared to 40 dB for RG8.
Connectors: LMR 400 is compatible with a lot of connectors that include most of the common interface modes such as non-solder and solder and reverse polarity pins. Most LMR compatible connectors use standard hex crimp sizes for outer attachment crimps.
Black PVC Jacket: Just like many others in the LMR standard comes with an Ultraviolet resistant Polyethylene jacket. Combined with an aluminum alloy that is plated with an oxygen-free copper, it is highly flexible and resistant to the elements that it can last for up to 20 years of outdoor service.
Posted by George Hardesty on 22nd Mar 2019