Splicing Coax

[fredg]

I want to splice a 2' section of RG6 (or RG58) to the end of my LMR400. Rather than use a bunch of adaptors (and since neither cable has an end now) I just want to splice them.

I found this on rec.radio.amateur.antenna:

"One successful method of splicing coax I have used ( and no doubt many
others ) is as follows :-

Lay the two ends of cable alongside each other, bind the two bared braids
together with 2 or 3 turns of 18 gauge copper wire, twist the two bared
inner conductors together, then use a hot iron and a liberal amount of
resin-cored solder to finish the job.

It is fast. It is cheap. It works. I have been doing it this way for 50
years and have never experienced any problems..."

 

[n5ims]

Install connectors and do it right. You probably can find a male for the LMR400 and matching female for the RG6 to minimize the cost & loss.

Just remember, people used pennies behind blown fuses for years without any issues as well (until they really needed the fuse and burned down their house).

 

[JESSERABBIT]

If you have or have a friend who has a voltage/ohm meter, you may want to check for shorts in the assembly prior to sealing it from the elements prior to connection to the antenna and the radio. That saves it from having to take it apart and re-do the operation.

 

[k8tmk]

As one of the other respondees mentioned, "do it right." When you use just a common splice on coax, you will likely upset the impedance of the cable. This can adversely increase the signal loss in the cable.

Randy

 

[zz0468]

Splicing coax is very poor practice in general, and especially poor when splicing cables of different impedences. That's the kind of thing that's only acceptable in an emergency to keep some critical service on the air, but otherwise it just makes you look cheap.

 

[fredg]

I also read on rec.radio.amateur.antenna (cannot find it now to copy and paste) that a properly done splice (as I pasted in my first message) can actually have LESS loss than a splice with connector, adaptor, connector.

Can't hurt to try the splice and see how it goes! This is for recieve only after all so it's not like I am going to hurt the radio....

And this will be just 2' inside, and I will probably use RG58 which is 50 Ohms like the LMR400....

The LMR400 is to stiff to go right to the scanner so I need a short patch cord. So I would have, for instance, a PL259, an adaptor to BNC, a BNC barrel then the BNC on the patch cord....

 

[NAVCAN]

geeze man. adapters may lose like 0.1 to 0.5db depending on frequency. And believe me, you CANNOT hear 0.1 or 0.5db. And their impedance is matched. Splicing a coax "your way" will give an impedance mismatch, will look like crap, and won't last nearly as long as a properly connectorized cable. Do it right.

 

[n5ims]

Or, you could have a male "N" connector on the LMR-400 (http://www.mouser.com/Search/ProductDetail.aspx?qs=PASb73EFAhahC5mb2BrCPw==), a female "N" connector on the RG-58 (http://www.mouser.com/Search/Refine.aspx?Ntt=523-82-6092-RFX) to make the splice and then a male BNC on the other end of the RG-58 to connect to the scanner.

You could can substitue UHF (PL-259) for "N" if desired.

 

[GTR8000]

First of all, ditch the crappy UHF (PL259) connectors and use N connectors. If your antenna has a UHF (SO259) socket, then you have no choice on that end, but get yourself an N female connector for the other end of the LMR400. Then get a short patch cable of RG-58 with an N male on one end and a BNC male on the other end.

EDIT: n5ims beat me to it!

 

[Williamb]

Lmr-400-uf

I also read on rec.radio.amateur.antenna (cannot find it now to copy and paste) that a properly done splice (as I pasted in my first message) can actually have LESS loss than a splice with connector, adaptor, connector.

Can't hurt to try the splice and see how it goes! This is for recieve only after all so it's not like I am going to hurt the radio....

And this will be just 2' inside, and I will probably use RG58 which is 50 Ohms like the LMR400....

The LMR400 is to stiff to go right to the scanner so I need a short patch cord. So I would have, for instance, a PL259, an adaptor to BNC, a BNC barrel then the BNC on the patch cord....

I am using TMS's LMR 400 UltraFlex with no problem right to the scanner. Using a BNC crimp and N connectors. Works great.

 

[mjthomas59]

I guess i don't understand the setup but it sounds like a crap shoot to me. You pay big bucks for "no loss" lmr400, then throw in a makeshift splice(or even properly done connectors) then put that through lossy rg-58 and throw a bnc on the end to boot. It seems as though with all the "add-ons" you could have just gone with rg-8 the whole run and called it good.

If you are talking about a couple hundred feet i suppose i understand the lmr-400, but then again if i had several hundred feet of lmr-400 at 70 cents a foot, i'd probably be more concerned with finishing it off right then hacking it together.

 

[GTR8000]

There's absolutely nothing wrong with using a short pigtail of RG-58 to bring the LMR400 to the radio/scanner. The attenuation for a 2' section of RG-58 is 0.3 dB at 1000 MHz. There is also nothing wrong with a BNC connector. How else is he supposed to connect the cable to his scanner that has a BNC jack? Have you ever tried to connect LMR400 directly to the back of a lightweight scanner sitting on a desk?

I do agree that it makes no sense whatsoever to spend all that money on good LMR400, only to do some hack job splicing and soldering of it. Cutting the outer shield and dielectric is only asking for all sorts of EMI/RFI to be introduced into the assembly. I can tell you that if you're worried about connectors introducing "loss" to your setup, cutting/splicing/soldering those cables together is an even worse way to go! Do it the right way and spend a few bucks to install good quality connectors on the cable.

 

[jhooten]

Put an N connector on the LMR
Connect the LMR to a properly grounded lightning arrester (I have PolyPhasers).
Make a jumper from the lightning arrester to the scanner.

Now you have changed the cable to a more flexable cable and added another layer of protection for the radio (and your house) while introducing minimal losses in the antenna system. You have just killed two birds with one stone.