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Lmr400?

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Billjones91581

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What is LMR400 and why is it so dang expensive? My friend's son who works at Comcast Cable can get me all the free RG11 I want. But is LMR400 better than it? Is it worth the investment? I listen to mostly the MPSCS (800 mhz digital trunked) and a few VHF high band channels and the VHF civilian air band. I have the Radio Shack 20-176 "Sputnik" mounted to a 10 foot pole on my 2 story flat roof.
 
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n5ims

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Take the RG-11. You won't find a better cost/results ratio using free RG-11, especially if the connectors are included. LMR-400 is good cable and rather low on the cost end for commercial coax. It appears to be "so dang expensive" if you compare it to the cheap low-quality TV cable you can find everywhere, but comparing it to who it competes with (RG-213, RG-214, etc) it is equal to lower cost. Comparing it to the commercial standard for tower runs (Andrew Heliax) it's quite a bit cheaper (and higher loss).

LMR-400 is fairly low loss cable and will perform better than what you normally find available for consumer-grade scanners like RG-58 or RG-8. It's a bit harder to work with and install since it's rather stiff cable, but still workable. For fairly short runs (75 - 150 foot or so) should perform well. For much shorter runs (50 foot or so) standard RG-6 is a good, cheap option.

The choice is yours. Go with expensive, low loss, and hard to work coax with for longer runs or when low loss is critical or save some money and use easy to find, work with, and find cable-TV coax for shorter runs where low loss isn't quite as critical.
 

Billjones91581

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Take the RG-11. You won't find a better cost/results ratio using free RG-11, especially if the connectors are included. LMR-400 is good cable and rather low on the cost end for commercial coax. It appears to be "so dang expensive" if you compare it to the cheap low-quality TV cable you can find everywhere, but comparing it to who it competes with (RG-213, RG-214, etc) it is equal to lower cost. Comparing it to the commercial standard for tower runs (Andrew Heliax) it's quite a bit cheaper (and higher loss).

LMR-400 is fairly low loss cable and will perform better than what you normally find available for consumer-grade scanners like RG-58 or RG-8. It's a bit harder to work with and install since it's rather stiff cable, but still workable. For fairly short runs (75 - 150 foot or so) should perform well. For much shorter runs (50 foot or so) standard RG-6 is a good, cheap option.

The choice is yours. Go with expensive, low loss, and hard to work coax with for longer runs or when low loss is critical or save some money and use easy to find, work with, and find cable-TV coax for shorter runs where low loss isn't quite as critical.
I'm not going to be using RG-6, RG-8 or RG-58, so I don't understand why you brought them up. I wanted a comparison of RG11 and LMR400 since I can get the RG11 for free. How thick is RG11 anyway?
 

LtDoc

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RG-6 is 0.332" in diameter. RG-8, and LMR-400 are 0.405" in diameter. So Rg-6 is slightly smaller cable. Another aspect of your installation is what impedance is required? RG-6 is 75 ohm cable, LMR-400 is 50 ohms. That difference isn't going to be much if all you want is to listen, but it does introduce some small losses.
In my opinion, since the RG-6 is free, and if the run isn't really close to 100 feet, use it. Maybe one draw back is that RG-6 is usually made using aluminum braid/shielding. That's only a concern when making connections, as in soldering aluminum isn't easy.
It's your choice, have at it.
- 'Doc
 

LtDoc

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Oops! I missed that one. The results are the basically same when using the TM calculator though. The RG-11 wouldn't be a good choice for 800 Mhz. But... it's free.
- 'Doc
 

mpddigital

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RG-11 is great for scanners and systems where you are not transmitting and need a good low loss drop cable. We sell a ton of it to scanner users. GOOD US Made RG-11 in 50k foot lots can be bought from the factory for less than 20 cents a foot.

Times LMR-400 sets the standard for low loss 50 ohm that is workable. Andrew/Commscope is pretty much as good without the metal tape being bonded to the dielectric. LMR-400 at a 50k ft buy costs us many times what RG-11 does. Even if the RG-11 is made by Times.

Why is it so expensive? The center strand is aluminum bonded with a copper plating to carry the signal. The dielectric is a special foam that is made to resist attenuation up into the microwave freqs with the outer layer of the dielectric having a metal tape bonded to it to act as your second layer. This is covered with braided copper that is tinned for soldering. LMR-400 costs much more to make, designed to bend 90 degrees in one inch without attenuation costs more. heck, 50 ohm coax in general costs more to make.

Whether you need LMR for your system is debatable. Free RG-11 is hard to beat. I think you should try it and see if it works for you. If not you may be able to go with RG-213, LMR-240, or even LMR-195 to meet your needs for less than 400 costs. Just do yourself a favor and don't think you are saving cash buying the cheap chinese crap as a substitute.

Have fun!
 

Nap

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Folks. RG-11 is 75 Ohms. It's designed for TV applications. If you're gonna use amateur radio equipment and antennas, please do yourself a favor and use 50 Ohms coax. Especially if you want to transmit.
 

W6KRU

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Folks. RG-11 is 75 Ohms. It's designed for TV applications. If you're gonna use amateur radio equipment and antennas, please do yourself a favor and use 50 Ohms coax. Especially if you want to transmit.
It sure sounds like the OP is talking about a scanner, not HAM equipment. He is using a sputnik antenna. 75 ohm cable will be fine if he can terminate it correctly.
 

mpddigital

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Termination can be an issue with RG-11. The diameter is essentially the same size as RG-213 or LMR-400 but the center conductor is much finer. Don't mess with F connectors. There are some very good 75 ohm BNC connectors available as well as PL-259s will solder on. Use the BNCs if you can.
 

Nap

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It sure sounds like the OP is talking about a scanner, not HAM equipment. He is using a sputnik antenna. 75 ohm cable will be fine if he can terminate it correctly.
Scanners are usually 50 Ohms input. At least GRE, haven't checked Uniden. Couldn't find any detailed info on the sputnik but it has a SO-239 connector and looks pretty much like a radio not TV antenna. My guesstimate is that it was designed with 50 ohms coax in mind.
 
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