Need cable advice

[WRFG619]

Hello, I have a gmrs base set up. I have a uhf base antenna about 20 ft up, I am going to raise it up to about 60 ft soon and need advice on what cable to run. I have heard on here gmrs is rated at 52ohms can anyone confirm that? At the moment I am using cb antenna cable rated at 50ohms.
A few years back the handhelds worked fine but now I have more trees and buildings around me so I need to do something.
I am using a 5watt handheld with the base antenna, I plan on just setting a repeater up but the setup I want is going to cost me about 5k and I don't want to spend alot until I go for that system.
Thanks.

 

[a417]

Are you referencing this post?

I believe that was a typo, as @krokus was on his phone, and i've never heard/seen 52 ohm specified cable. Most likely he meant 50 ohm which is quite common, and there is nothing in any specification (that i am aware of) for a radio service that specifies a particular cable impedance.

I've attached a screenshot from Tessco below, they don't have a section for 52 ohm, but they do have 50 / 75 ohm and a variety of VASTLY more expensive stuff.

If you can get your hands on LMR-400 UV rated, that'd be a very good starting point for your antenna system. LMR-400 from the antenna thru a Polyphaser to a termination point, then a jumper wire from the termination point to the radio. When you get your repeater (good luck!) then you can eliminate the termination point and re-end the wire so it goes directly into your repeater antenna port. Less connectors, less loss.

 

[jim202]

If you have any intention of using the same coax cable for any repeater work, do not use any version of LMR coax cable. The aluminum foil shield and the copper braid combination is well documented in many threads to cause repeater noise that you will not be able to get rid of. The LMR coax cable is known to leak moisture into it. This allows oxidation to form between the different shielding material and start acting up as a diode in the use of a duplex operation.

You would be much better off with a coax cable that doesn't use different types of material for a shield. Spending a little more on the coax cable is a much better plan up front. The type of coax will depend on the length of the run and how sharp of bends you need to make.

Jim

 

[mmckenna]

Yeah, 50Ω/52Ω impedance, not a big deal.
The radio, antenna and coaxial cable will work ideally if it's all the same impedance. Your radio will be 50Ω. Any commercially available antenna you buy will be 50Ω. So should your coaxial cable.

As coaxial cable gets longer, the inherent losses go up. So moving your antenna higher is a good thing, but if you don't use good coaxial cable, you'll blow most of your gains in the longer cable.

I agree with Jim. If your plan is to do a repeater at some point, install the right cable and antenna now. You may find that getting the antenna up higher fixes all your issues and a repeater isn't necessary, so it might save you money in the long run.

Use a really good antenna. The labor/risk of installing one up high should discourage you from installing a cheap antenna. You want it to last as long as it can.
Use high quality coaxial cable designed for your application. Heliax cable should be the goal. at 60 feet, 1/2" Heliax should be fine. LDF4-50A is the model number for the cable. Be aware the stuff is pretty stiff, so you have to route it carefully. It's also standard practice to NOT connect it directly to the radio or antenna, the stiffness of the cable will bust off connectors. Use a short whip of smaller cable to make the final connection on each end.

Also, going higher puts you more at risk for lightning related issues. National Electric Code requires proper antenna support grounding and lightning suppression on your coaxial cable.

 

[a417]

Thanks guys, I didn't know that part about the LMR shielding.

 

[prcguy]

The different shielding metals in LMR cables is only a problem in full duplex systems like the feedline on a repeater, not a problem on a simplex radio installation. In my opinion and probably others, LMR400 would be the most cost effective cable balancing cost, size and loss. Bigger is better but at more $$ and the hassle of running a garden hose size cable through walls, etc.

Thanks guys, I didn't know that part about the LMR shielding.

 

[mmckenna]

That's a good point, but the OP is talking about eventually installing a repeater. Might be more cost effective to just go with the right antenna and coaxial cable now.

I plan on just setting a repeater up but the setup I want is going to cost me about 5k and I don't want to spend alot until I go for that system.
Thanks.

 

[WRFG619]

Thanks for the reply. When I get the repeater ( If I can afford it ever ) this antenna will more then likely be left where it is and reused for another radio or scanner. At the moment I'm just trying to clear some trees and new buildings, I am on a hill and up higher than most of the locations I'm trying to reach. The reason I was looking at a repeater setup is to clear a hill to the 3 1/2 miles west of me, I don't think I'll be able to clear the hill as it is about 100ft higher. To get the antenna that high it looks like it would cost over $12,000 and there's no way I can afford that plus at that point a CB would be so much cheaper. some of us use CB's and we get pretty good coverage here but I want to have handhelds too and I haven't seen a good CB handheld.

 

[mmckenna]

OK, so if no plans to use a repeater with this setup, and using it for either GMRS, CB or scanner, with the appropriate antenna, LMR-400 would be a good economical choice.
Just make sure you properly waterproof all exterior connections, you use a lightning suppressor and proper grounding per the National Electric Code. Sticking a big metal thing up in the air can draw the ire of the lightning god, especially in Oklahoma.

 

[krokus]

Are you referencing this post?

I believe that was a typo, as @krokus was on his phone, and i've never heard/seen 52 ohm specified cable. Most likely he meant 50 ohm which is quite common, and there is nothing in any specification (that i am aware of) for a radio service that specifies a particular cable impedance.

I've attached a screenshot from Tessco below, they don't have a section for 52 ohm, but they do have 50 / 75 ohm and a variety of VASTLY more expensive stuff.

Many "50 Ohm" coax cables are actually 52 Ohm. Look at the datasheets, especially for RG-58 and RG-8 cables.

 

[a417]

Huh, learn something every day!

 

[WRFG619]

Many "50 Ohm" coax cables are actually 52 Ohm. Look at the datasheets, especially for RG-58 and RG-8 cables.

I checked that out that's cool. I think I may go with the LMR-400. The company I talked to about the repeater said that I still may have issues with receiving at the location even though I may be able to transmit so I may not even mess with that. I can be miles out and hear people transmitting from my house but they can't hear me.

Thanks mmckenna for reminding me about using a lightning suppressor and proper grounding. I normally do but I didn't even think about it on this build, I been thinking about the cable to use and where to get guy wire. My 20ft poles have been bent over so many times and bent ( Sorta ) back I know I need to make sure this one is solid when I put it up.