If you was gonna put up another Tower or antenna

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ScanMaine

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If you was gonna put up another antenna on another 100 ft tower what would you use for Coax RG8 or LMR400
 

ScanMaine

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Well whatbout rg8. Ibrunning it now. But I hear the 400 the best. I just want the best I can

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n5ims

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If you was gonna put up another antenna on another 100 ft tower what would you use for Coax RG8 or LMR400
Neither. I'd probably use some LDF4-50A (LDF4-50A) or better coax, especially if I wanted good performance on the higher frequency bands like 800 MHz. 1.971 dB loss @ 800 MHz over 100' for the LDF4-50A vs. 3.646 dB for the LMR-400 (lower is better). RG-8 (Belden 8237) would give you 6.419 dB loss. If you go with some larger coax like LDF6-50A you could drop that loss down to around 0.79 dB.

You'll end up with more loss than that since 100' will only get you down the tower and you'll most likely need more coax to get your signal from the tower base to your radio.
 

ScanMaine

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Ya. We don't have much 800 hear on Maine so I'm still batting the ideas

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n5ims

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Ya. like I said I have RG8 here now and I like it but I want the BEST
Oh, you want the BEST (and we were being practical with our answers, shame on us). Get some 6 1/8" rigid coaxial line (like ERI - MACX650). You'll have a very minimal 0.147 dB loss @ 800 MHz over 100'.

You may need a stronger tower (the coax is about 8 lbs/foot) and a larger tower to handle the coax's large size. Don't forget the springs to secure it to the tower (the copper will expand/contract at different rates than a steel or aluminum tower so the springs are needed to compensate). Be careful with your path from the tower to the radio though since you'll need support for the coax (generally a metal bridge) and bends must be made in 90 degree or 45 degree angles unless you want to have them custom make one.
 

mmckenna

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A what??? LOL got a picture
Tower Top Amp for my 800MHz system, the white can under the top antenna.
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It's about 100 feet from the radio equipment, so it's all fed with 1 5/8" Heliax.
The type of coax you need will depend on how much signal loss you are willing to accept as part of your radio system. For 800MHz, you are going to lose a lot of your signal in RG-8 or even LMR-400, that means that weak stations won't even make it to your receiver (you won't hear them). For those sorts of frequencies and that sort of distance, you'd really want something like 1/2" or 7/8" heliax if you want to get weak stations.

It's all about how much money you have and how much signal loss you are will to accept.
LMR-400 would not be the best for this sort of install.
 

DisasterGuy

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I would have to agree with using nothing less than 1/2" heliax. I would likely use 7/8" as mentioned and would indeed use a TTA for 800MHz.


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