Antenna & Coax

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teebee

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Dec 10, 2001
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Lake Charles, LA
I have an Antenex B8965C antenna with a magnet mount. Using it to monitor 700 and 800 mhz. (any better mobile antenna's with mag mount for 700 & 800 recommendations, please). I have to change the coax on it because it is way to short. The coax is RG8x. Should I try and replace it with RG8x cable or is there a better/lower loss cable than this one. I have looked at LMR-240 and LMR-300 50 ohm and 75 ohm cables. They both seem to be RG8x cable. Also I have noticed some people use RG6 cable for mobile antenna's. Isn't RG6 75 ohm cable and isn't it recommended to use 50 ohm cables on scanners. Which of the two has better performace and lower loss 50 ohm or 75 ohm. According to Times Microwave there LMR-240 and LMR-300 is also offered in 75 ohm cable. Could someone advise the best performance cable and what ohms is best to use. Thanks
 

af5rn

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Apr 4, 2008
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N. Tex / S. Fla
In a mobile application, the difference between the best and worst coax is negligible. We're only talking about 15 feet max. Not enough length to create much loss. RG8X is a great choice for mobile and even short (<50 feet) base runs.

It never hurts to go with better coax, so if you've got money burning a hole in your pocket, and an obsession with having only the best, then feel free to get some LMR. But honestly, with a 15 foot run, you won't notice any real difference between the best LMR and the worst 750ohm.

While the diff between 50 and 75ohm performance in a scanner application is not significant at short distances, there is no good reason to use 75ohm coax. It's no cheaper than 50ohm, unless you're getting it for free, and, at least theoretically, it's not as well suited.
 

SAR923

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Dec 19, 2002
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LMR400 tends to be real hard to bend and get through any normal size holes in a vehicle too. The thin RG-8x is fine for short runs and is actually less liable to have center cnductor problems since it's so flexible. As was stated, 50 ohm or 75 ohm impedence cable will work equally well with a scanner. Transmitters are another story but scanners really dn't care much about a 25 ohm mismatch.
 
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