LMR 400 connector question

I am going to replace my existing coaxial wire with a single lay of LMR 400 with a N connector on both ends of it. My question is when i go to hook this up to the F connector on my ST-2 antenna, should i cut the N off of the wire and replace it with a F connector, or should i use an adapter? Also wondering if i should use an adaptor on the end going into my BNC splitter or cut the N off and replace it with a BNC connector. Im laying about 75ft of wire and i want to eliminate loss on both ends as much as possible. Any information on this is greatly appreciated.

Also looking into the best way to cut the ends off and replace them if it is needed.

I personally would just use an adapter ( just my personal option ) depending on what freq your on I don't think you will have very much loss with lmr 400 its pretty good stuff

I would use an adapter at the antenna end. The loss will be so small that you will not notice it. I'm not sure if there is a female n to a F connector but there might be. I would use an adapter at the BMC end also as working with a bnc plug and attaching to lmr 400 would be a challange.. All the bnc's I have are for rg8x or rg58. All of the text bok talks about adapter losses , they don't total 3db, and 3db is 1/2 an S unit, and thats barfely decirnable to the human ear.Probably the added loss will be in the neighborhood of 1db or less. Most everything I have read or experienced that with heavier and less flexible coax, you end up attaching to a patch cord, or more flexible and lighter weight to reduce the strain on the radios connection point.

LMR-400 is pretty stiff. I'd strongly recommend using a flexible jumper if at all possible.
I've never seen an "F" connector for 50 ohm LMR-400, but that doesn't mean they don't exist.

It would be easy to do a simple N female to F adapter using smaller coax, and it will take a lot of strain off the connection point. If I recall correctly, the ST-2 uses a 300 ohm to 75 ohm balun, so this might not be quite as necessary as on 50 ohm fed antennas, but it certainly won't hurt.

They do make the F connectors but they are about $30 as I was toying with the only one connector freaking out about 1/2 a dB. I just put a PL259 male soldered on and a SO239 to F adapter to my Electroline. I'm doing low band to 800 no problem with a discone.

mmckenna said:

LMR-400 is pretty stiff. I'd strongly recommend using a flexible jumper if at all possible.
I've never seen an "F" connector for 50 ohm LMR-400, but that doesn't mean they don't exist.

It would be easy to do a simple N female to F adapter using smaller coax, and it will take a lot of strain off the connection point. If I recall correctly, the ST-2 uses a 300 ohm to 75 ohm balun, so this might not be quite as necessary as on 50 ohm fed antennas, but it certainly won't hurt.

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Thank you for the good direction. I am just going to use adapters and not cut any of the wire. Im hoping i wont get to much loss with the adapters. I am running this into a cheap BNC splitter for now until i can get my one of the super low loss ones that cost a bit more.

What are the "Jumpers" you are referring to?

Coolant113 said:

What are the "Jumpers" you are referring to?

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A short length of smaller, more flexible cable. It's standard practice in the industry to do this. When thick, less flexible cables are used, connecting them directly to antennas or other hardware can be hard on the connectors. Usually a short piece of coax is used between them to provide some strain relief.
For what you are doing, a foot or so of standard RG-58 with an N connector on one side and an F connector on the other will make life easier. There will be a fraction of a dB additional loss, but it likely won't be noticeable and will help prevent damage to the radio and antenna connectors.

One thing to think about is using the 75 ohm version of LMR-400 (https://www.tessco.com/products/displayProductInfo.do?sku=478339) instead of the standard 50 ohm version. Your ST-2 as well as most standard splitters are 75 ohm and should provide you a better match as well as slightly lower loss. You should order it with an F connector (https://www.tessco.com/products/displayProductInfo.do?sku=474375&fromSuggestion=true) on the antenna side and a BNC connector (https://www.tessco.com/products/displayProductInfo.do?sku=567050&eventPage=1) on the splitter side to eliminate the adapters.

I appreciate all the replys. I got my LMR 400 cable today in a 100ft length, with N connectors on both sides. I took a look at the side of the wire and it says it is 50 ohms. I also have the adapters on order, which I will try out first.

My next question what is the difference in LMR 400 50 ohms vs 75 ohms? Will this have an effect on anything?

Coolant113 said:

My next question what is the difference in LMR 400 50 ohms vs 75 ohms? Will this have an effect on anything?

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One is designed for a 50 ohm impedance and the other for a 75 ohm impedance. Use the 50 ohm version for 50 ohm applications and the 75 ohm version for 75 ohm applications. That's basically the difference. For receive-only applications you won't have any serious issues using the other version, you'll just have a small increase in loss due to the impedance mismatch.

Coolant113 said:

I got my LMR 400 cable today in a 100ft length, with N connectors on both sides.

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I'd be concerned about the extra loss you're going to have if you're using a 100ft length and only need a fraction of it.