View Full Version : 3', 6' or 9' Cables?

Unkle Buck
12-01-2015, 07:00 PM
I was told my cable lengths need to be in multiples of three feet. Three, Six, nine, etc..
Could someone explain this in not to technical terms? I do not understand why.

12-02-2015, 07:14 AM
It's a CB myth and mostly snake oil. Use what is needed to get from point a to b. It's all relative to the 36ft that is 11m or 27mhz band. Some think that multiples of 3ft are needed to keep everything in line with the 36ft for 11m. It's snake oil and don't fall for it. Use what your need. Yes making coax jumpers in 2 or 3ft increments is easy and normally a 3ft coax jumper is all that is needed. Some may require longer coax jumpers to go to an amp or somewhere that the other equipment is located, but I have used 20ft, 25ft, 8ft, all different lengths and as long as your system is matched at or near 50 ohms. If you are having to use specific lengths as such stated, you may have mismatch issues somewhere as normally whatever reaches from point A to B should work the same, I.E. A 2ft coax jumper shouldn't show any difference to a 3ft one. It's some peoples belief and some times it does work, but it's normally a band aid for another issue. Now when speaking in terms of long runs, they normally come in 50ft increments, and I don't think that is a multiple of 3ft now is it?? Maybe my math is different than some others LOL!! Take it for what it's worth. Use what reaches from point A to point B and be done. JMHO. Good day. And this is a touchy subject so let the war begin LOL!!!!

Unkle Buck
12-02-2015, 01:56 PM
Thanks. Again, I am new to all this and have been doing a lot of reading and burning brain cells to understand it all. I want to be able to talk to folks about 40 - 50 miles away routinely. I will worry about skip and all that good stuff later.
I am going to try to assemble everything tonight and see if I can get it up and running with the cables I have.

12-02-2015, 03:44 PM
If it's a base setup and you have no major obstructions you should be able to get out that far conditions permitting. That said, get your antenna as high as possible if it's for local use. Not sure what your antenna setup is, but make sure it's at its best before you add an amp!! But the coax deal is BS and of you bed to use a specific length of coax for an antenna it either will specify so or there are other issues such as vswr, impedance mismatch, vswr, both at the antenna and at the radio. Lots to go through. Get your antenna system best it can be! Good coax, connectors, and a proper install of grounding and antenna system, will all help.

Unkle Buck
12-02-2015, 06:05 PM
My antenna is a Solarcon99 about 50 feet in the air, above surrounding houses and trees. The CB Base station is, I think an old Cobra, but I would have to look to be sure.

12-03-2015, 07:20 AM
You should be fine with a 100ft run of rg8x or lmr240, lmr400 would be the best bet, especially if you are running power. Jefa Tech makes some good looking and from what others have said, quality coax. Get 100ft of some LMR400UF type coax from there. The UF stands for Ultra Flex and is a more flexible coax. JMHO. That and some good amphenol or similar type connectors. Andrew, Eupen. Commscope all make connectors for the above coax's and they are quality. The amphenol ones work well. Silver tip with a good insulator. Anyway, you may have this already covered but just in case. Some food for thought. Have a good day sir. And also, if you have extra coax left over, coil it up nice. It won't hurt a thing. Be safe and good luck getting all setup up.

12-03-2015, 08:27 PM
It's important having good quality cable, especially on long runs. LMR 240, RG8U or RG213 are good cables to start with and will last a long time, cost about $1 per foot. If you can afford $2 per foot go with the LMR400 flex. Don't forget a good solder job with a good quality connector. Good Luck..........Steve

12-05-2015, 08:13 PM
If you have access to some upper grade coax, see if RG-214 is available. The shielding is a higher percentage versus RG-213. It also has a polypropalene insulator. Make the coax as long as needed and terminate. Outside installation is simple, connect tightly and wrap with black electricians tape and smother in silicone sealant. That will last 25 years and when you need to disconnect, cut through the sealant and tape and peel back.

01-03-2016, 11:21 AM
I have found a 3footer behind the radio will show lower swr sometimes ,be it snake oil or what ever , or lying to the meter i,am not sure ..Also i no for sure a 9 footer between radio and amp helps ..Have fun ....

01-05-2016, 04:55 AM
Read this and maybe it will make you understand what I mean by fooling the meter. http://images.tapatalk-cdn.com/16/01/05/3c1626866c18ede071fbd860b685220f.jpghttp://images.tapatalk-cdn.com/16/01/05/9a7f25f51a5784835d606c5707c4b9fa.jpghttp://images.tapatalk-cdn.com/16/01/05/3f107adc268cdb709ca4270ccffe0d2e.jpg
Read these and then re read them again. They really will open your eyes to a lot of BS being spread!!!

01-08-2016, 02:16 PM
When all is said and done, the important part is to get as much RF energy to the antenna feed point as possible. Every termination, every length of coax creates a one or two db loss in what gets to the antenna. Lengths can be important but anything over half the wavelength of the operating frequency is good and only helps keeping wavelength segments up to 5 WL long. SWR is most important as is robs directly from the ERP and results in distortion and harmonic generation.