Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Mobil install..Coax length??

H

hammer0630

Active Member
Sep 10, 2011
474
64
38
Catskill mountains N.Y. Southern California native
I am replacing my Cobra 29LTD radio and replacing my cheap oil coil antenna with a Wilson Trucker 18 inch shaft and a Galaxy DX959 modded out. What I am not sure of does Coax length make a big difference in mobile performance? I have right now in my Tacoma I believe is 18 feet of coax which is way to much causing me to coil it up under the truck. I bought 9 feet of coax that I think will be just long enough..am I doing the right thing here?
 
Last edited:

hammer0630 said:
I am replacing my Cobra 29LTD radio and replacing my cheap oil coil antenna with a Wilson Trucker 18" shaft and a Galaxy DX959 modded out. What I am not sure of does Coax length make a big difference in mobile performance? I have right now in my Tacoma I believe is 18' of coax which is way to much causing me to coil it up under the truck. I bought 9" of coax that I think will be just long enough..am I doing the right thing here?
Click to expand...

Coax length in a mobile environment is to short to drastically affect performance. Also shortening the feedline length using the same type of coax will also never affect performance, assuming the coax is good and the ends were put on properly.

There are people that swear by that 18 foot length, but they misunderstand what is happening, and they got their length wrong...

Going from 18 feet to 9 inches? I generally add an extra foot or two just for adjustment room and ease of access for the radio. At 9 inches you don't even have that... :D


The DB
 
I have run 18, 12, 9, and 6 foot lengths with no difference in performance or tuning.

Sent from my SCH-I545 using Tapatalk
 
I wish I had a dollar for every time someone asked this question or thought that length was critical for mobile installations, or even any installation for that matter. There is lots of misinformation out there on the internet in this regard. Most of it comes from people repeating what they heard without having an understanding about it. Coax length does NOT matter if the antenna is properly tuned and that is whole idea in the first place isn't it? To tune the antenna itself properly and not simply fudge the system by changing coax length until the SWR meter reads what you want it too?
 
Last edited:
  • Like
Reactions: 1 person
Length shouldn't matter. I use whatever reaches and add a couple feet just in case, I think my current mobile coax from antenna to amp is 21 or 22ft of lmr240. Whatever reaches will work like posted. If the swr reading changes, there are other issues. JMO. Use what reaches.
 
222DBFL said:
Length shouldn't matter. I use whatever reaches and add a couple feet just in case, I think my current mobile coax from antenna to amp is 21 or 22ft of lmr240. Whatever reaches will work like posted. If the swr reading changes, there are other issues. JMO. Use what reaches.
Click to expand...

I didn't think that 9 feet to 18 feet was any concern as to loosing any measurable signal due to line loss but what do you do with 9 feet of extra coax was my real concern. I bought the 9 feet to try and eliminate coiling it up which could have a real affect on transmit. I went to Wilson antenna's home site and they recommend 18 feet rather strongly. Since they mentioned it twice it put me back into what do I do?
 
hammer0630 said:
I went to Wilson antenna's home site and they recommend 18 feet rather strongly.
Click to expand...

Firestik pushes that length as well. Its a shame companies fall for these myths and actually help spread them. Unless you are doing something with phasing, or using something more advanced than an SWR meter, then there is no point to using any specific length.


The DB
 
  • Like
Reactions: 1 person
hammer0630 said:
I didn't think that 9 feet to 18 feet was any concern as to loosing any measurable signal due to line loss but what do you do with 9 feet of extra coax was my real concern. I bought the 9 feet to try and eliminate coiling it up which could have a real affect on transmit. I went to Wilson antenna's home site and they recommend 18 feet rather strongly. Since they mentioned it twice it put me back into what do I do?
Click to expand...

If Wilson is so adamant about 18' why was the coax on the mag mount I just got from them 17' 4 1/4"?

Sent from my SCH-I545 using Tapatalk
 
i run 9 feet of rg213 from antenna to amp and 6 feet of rg8x from amp to cobra 29,,,,antenna is 102 inch steel whip on a modified c 32 hustler ball mount so that it accepts a pl259,,, there is a 6 inch military style spring that i got at a state auction about 30 years ago,, the whip i bought about 1980 its an antenna specialist... its all mounted on my aluminum toolbox mounted on my 99 ford ranger,, 1.5 or less from 26.5 to 28.5,, i know it gets out good here in florida i can when conditions are quiet easily communicate 30 miles or more....oh by the way the amp is only 50 watts so no big power pig here.... just some thoughts 73s midnight special
 
Some antennas are designed (poorly) and actually rely on the coax cable radiating as part of their "performance". In this case there may indeed be a "proper" length of coax that will yield a good SWR. Anyone that understands antenna theory tends to avoid such antennas like the plague.
 
  • Like
Reactions: 3 people

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back