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Memory refresher. RG58/u VS RG6

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scanmanmi

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#1
When I switched the base to RG6 for 800mhz it worked great. I am looking at mobile 800 antennas but the seperate bases come with RG58/u. Please refresh my memory on what the /U means because I don't think 58 would be good for 800mhz. Should i get a mobile base with RG6 (if I can find one)?
 
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#2
The "RG" designator dates back to at least WW2 and comes from a "Radio Guide" military specification. The "U" stands for general utility use, probably from the same era.

Personally I don't use RG-6 for 50 ohm radio/antenna use and instead go with LMR240 or larger cables when loss becomes a problem. You can find NMO type mounts that will accept LMR240 cable or transition from RG-58 to something larger within a few inches of the antenna if the RG-58 is permanently attached.
prcguy


When I switched the base to RG6 for 800mhz it worked great. I am looking at mobile 800 antennas but the seperate bases come with RG58/u. Please refresh my memory on what the /U means because I don't think 58 would be good for 800mhz. Should i get a mobile base with RG6 (if I can find one)?
 

jwt873

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#3
For mobile use the feedline length will only be around 4 to 8 feet. Practically speaking, the loss presented by RG58 for those lengths is negligible.

Plus, I don't think you'll find commercially sold antenna systems with RG6 on the antenna mounts. The antennas will be for 50 ohm systems and RG6 is 75 ohm.
 
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#4
I would avoid using RG-6 in a mobile application, the cable is not designed for that environment and you will not find NMO mounts that are designed for that cable.

Look for mounts made with LMR-195 or RF-195. Same size as RG-58 so you can use the same connectors and it's less loss which makes a difference at 800MHz.

LMR-240 would be better, I've made up mounts with LMR-240 but I've never seen them come pre-built.
 
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#5
I would avoid using RG-6 in a mobile application, the cable is not designed for that environment and you will not find NMO mounts that are designed for that cable.

Look for mounts made with LMR-195 or RF-195. Same size as RG-58 so you can use the same connectors and it's less loss which makes a difference at 800MHz.

LMR-240 would be better, I've made up mounts with LMR-240 but I've never seen them come pre-built.


Tessco just subbed 130+ NMO kits on one of my orders for kits with RG-8x instead of RG-58. RG-8x is the same diameter as LMR-240 for those who didn’t know.


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#6
I beleive RG58 are not specified for use over 450MHz. What is important in a modern vehicle with all its computers and datasignals on all wires is to use a good shielded coax, double screen. There is low loss double screen version of RG58 that are suitable to use.

/Ubbe
 
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#7
RG-58 will work well up past 450MHz. Depending on what manufacturer you look at, you'll see it spec'd up to 5gHz.
Of course performance is going to be pretty bad up that high.

As for 800MHz use, it'll be fine if your cable run is reasonable. I've got 40+ 800MHz mobiles at work and every one of them is using RG-58 coaxial cable between the radio and the NMO mount.

While it's not ideal, it'll work. For comparison…
10 feet of RG-58 will have 1.4db at 800MHz.
10 feet of LMR-240 will have 0.7db at 800MHz.

You won't hear that 0.7dB of difference in most cases, maybe at the fringes of coverage. Still, the price difference isn't much. Personally I'd probably go for the LMR-240 for my own use. At work, I'd have no problem using RG-58. Our system is designed well enough that 0.7dB of extra loss is going to break the system.

One thing to consider, though, is that LMR-240 has a solid center conductor, RG-58 has a stranded. It's easier to run RG-58 in a vehicle, although 240 is not impossible, it's just stiffer.

And, as others have said, You won't find RG-6 in a premade NMO mount kit. No reason for manufacturers to use a 75Ω cable in an environment that traditionally uses 50Ω.

For reference, 10 feet of RG-6 at 800MHz is going to have .87dB of loss. Better than RG-58, but again, you'll probably not be able to notice the difference.
 
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#8
RG-8X is the same size as LMR240 but its not the same. Last month I got a bunch of LMR240 cable assys from Talley and they subbed RG-8X on some of them without asking me. I complained because the needed frequency range was past 2GHz and I had quoted LMR240 to my customer. Talley had to make them over again with LMR240 at their cost.
prcguy

Tessco just subbed 130+ NMO kits on one of my orders for kits with RG-8x instead of RG-58. RG-8x is the same diameter as LMR-240 for those who didn’t know.


Sent from my iPhone using Tapatalk
 
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#9
RG-8X is the same size as LMR240 but its not the same. Last month I got a bunch of LMR240 cable assys from Talley and they subbed RG-8X on some of them without asking me. I complained because the needed frequency range was past 2GHz and I had quoted LMR240 to my customer. Talley had to make them over again with LMR240 at their cost.
prcguy
Yea...Tessco subbed them and forgot to send the Mini-U connectors on us (we had enough to get the job done with RG-58).
 
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