Squashed aerial cable

J

JimC

Well-Known Member
Joined
30 Aug 2001
Messages
1,570
Location
Lancashire
Visit site
When raising my mast the RG58 vhf aerial cable got pinched between the heel of the mast and the mast step, giving it a flattened cross section over a length of about 2 cms. The outer sheath wasn't marked. I squeezed it back to circularity with a pair of pliers and did a continuity check from the plug end. This showed the correct 10K ohm resistance for the Vtronix aerial so I'm inclined to think no harm done. Am I right?
 
I’m no electronician but I would be concerned about the increased likelihood of failure, possibly at an inconvenient time. I await expert views but I think I would want to cut our the damaged section and rejoin, though this would clearly be suboptimal.
 
Co ax works like a capacitor, an electric field is set up between the inner and the outer sheath. Anything that changes the cables diameter, or disturbs the outer sheath can cause energy to be reflected in directions you don't want it to go.

The resistance doesn't matter, what's the VSWR on the antenna and cable?

It may be easier to add in a proper connection and cut out the damaged part (BNC, TNC etc.)
 
If the outer sheath is intact I'd be loath to cut it and replace with a joint (ie future failure point) at deck level - especially if it works as is.
 
st599 said:
Co ax works like a capacitor, an electric field is set up between the inner and the outer sheath. Anything that changes the cables diameter, or disturbs the outer sheath can cause energy to be reflected in directions you don't want it to go.

The resistance doesn't matter, what's the VSWR on the antenna and cable?

It may be easier to add in a proper connection and cut out the damaged part (BNC, TNC etc.)
Click to expand...
Whilst there’s some truth in this, I suspect the cable will function reasonably well now it’s been squashed back into shape. However I’d probably replace it when convenient.
 
KevinV said:
If the outer sheath is intact I'd be loath to cut it and replace with a joint (ie future failure point) at deck level - especially if it works as is.
Click to expand...
You can't see the outer sheath, it's inside the insulated cover.
 
It won't be as good as it was, but considering the trouble with getting the mast down again and replacing the cable, I'd go with it. Try using the VHF, transmit will find any weak patch of coax insulation. Rx will probably be OK.
 
Don't worry about it, stick a new length of cable into your spares locker, if you start to get continual interference then you may consider changing it. If it works don't fix it.
 
Should be OK as said. However if yoiu are concerned how about fitting an emergency antenna on stern rail with a cable and plug going to back of radio. In case of failure or mast loss. ol'will
Ps I jambed main halyard polyester rope under my mast foot. It cut the 10mm rope badly. I am surprised you did not cut the cable. ol'will
 
Do some test calls over some decent distances if it Tx/Rx OK ...fine.
If the outer casing has not been breached and the shielding has not been exposed , doubt the inner insulation will have been damaged.
You could borrow a SWR meter and check but would suggest a real world contact might be a better reassurance.
Would also depend on if your normal boating is well offshore or usually within sight of help ?
 
You must log in or register to reply here.

Share this page

Top