Compromised VHF Coaxial cable problem

CaptainTonyM

Recruit
Joined
Aug 24, 2009
Messages
4
I have a Raymarine ST60+ wind Indicator that will deviate 180 degrees plus anytime I key the VHF. Raymarine suggested I check the VHF coax cable for damage. Sure enough, there is a V shaped tear in the coax cable where it enters the PVC pipe within the mast. The copper braid is visible if I pull up on the tear. My question is this: Can the cable be mended to 100% integrity by taping over the cable at the tear, or am I going to have to replace the cable in its entirety, as there isn't enough cable at that tear point within the mast to do a cut and put in a connector? If I have to replace the cable, is there a rule of thumb as to how much cable I need? The mast is 58 feet high. The present cable appears to be about 65 feet.

Tony M
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,755
Re: Compromised VHF Coaxial cable problem

Something else is wrong. Just because you can see the shield (the braid) does not mean that is the issue. The outer jacket merely protects the inner layers of the cable. Either the braid is also broken, a connector is bad, or the inner conductor has broken and is intermittent.
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: Compromised VHF Coaxial cable problem

To answer your question, a properly terminated cable can be any random length.

hope it helps
John
 

jhebert

Ensign
Joined
Jul 24, 2005
Messages
902
Re: Compromised VHF Coaxial cable problem

The insulation atop the outer conductor of a coaxial cable plays no part in the shielding of the cable.

There is a rule about lengths of cables:

Any cable cut to length will be too short
--Murphy.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,755
Re: Compromised VHF Coaxial cable problem

I can affirm Murphy's Law regarding this stuff. I once cut a cable to length twice and it was still too short!!!!!!!!!!!!!!!!!!
 

Boatist

Rear Admiral
Joined
Apr 22, 2002
Messages
4,552
Re: Compromised VHF Coaxial cable problem

How near is this wind indicator to the antenna?
Is the wind indicator in the radiation Pattern of the antenna?
Is this a new problem or has it always been that way?
I assume you have the standard 3 foot base loaded 3db gain antenna.
If the wind indicator is near the antenna and in the radiation pattern then I think this might be normal.
I would first try lowering the wind indicator out of the antenna radiation pattern.
Also how well does the radio work? Can you get about 12 miles boat to boat?

Coax bad outer cover can have a very big affect on coax cable.
They are correct that current flow thru the brad and the outer sheild would have no affect if it is totally dry and the sheild is not broken or shorted to ground.
However the outer cover also keeps water out of the cable.
Water inside the cable can short it out completely. This is a big problem with Coax that has a foam core. Even if either end is not sealed completely from water it can get into the cable and make the cable an affective short and the braid an effective radiator.
However if this happends it would also limit the range of your transmiter.
You can use a VHF or Ham 2 meter field strength meter to check the signal output of the antenna and the Braid.
Good Luck and let us know what you find.
 
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