Can anyone shed light on shortening the coaxial cable fitted to a V Tronix whip antenna? It arrives with about 60 feet of cable, far too long for a Seal22. I have vague memories about needing to shorten by multiples of the typical wave length to avoid losses in efficiency. Similarly, if I cut the cable to fit an in-line connector (to simplify rigging/derigging when trailersailing) will this make any difference?
regards to all,Tony Nield S22 Dee Rover

Hi Tony

I've not had any problems shortening cables and fitting joints.
I use good quality BNC type connectors and solder at the appropriate points. I have a joint at the base of the mast for my DSC antenna and a stub antenna mounted on the rail for my AIS. This has a very short cable and works fine.

John Williams
275/60 CRYSTAL

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Hello John
I'll give it a go. I was reluctant to chop off a length of the aerial until I was sure. Thanks for your advice
regards Tony Nield S22 Dee Rover

quote:

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Originally posted by John Williams

Hi Tony

I've not had any problems shortening cables and fitting joints.
I use good quality BNC type connectors and solder at the appropriate points. I have a joint at the base of the mast for my DSC antenna and a stub antenna mounted on the rail for my AIS. This has a very short cable and works fine.

John Williams
275/60 CRYSTAL

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Don't think there is a problem with shortening the cable....think it is the antenna length that is important.

Paul Burton.

Parker 235/ 40 Lady Penelope...

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You won't notice much difference in performance by shortening the cable at VHF frequencies. The important thing to remember is keep water out of coax cable as it will wick up the braid and may be absorbed by the central core insulator altering the electrical characteristics of the cable, and solder the tip and shield if possible, If I cannot solder the shield/braid then I smother it in silicone grease before screwing it into the plug.
You can get as much as 1db signal loss through a VHF connector, so if you have 3 connectors (joints) then you could have halved the power going to the antenna. So try to keep them to a minimum.
3db = double the power, -3db = half the power.


Mike Edwards
Seal 28 "Aztec"

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Thank you all for the advice and comments. I have now shortened the cable to suit the S22, so it has one in-line socket in the cabin. The cable feeds into the cabin through the little dorade ahead of the mast and plugs into the inline socket adjacent to the PHside trotter box, where it is safe and dry. From there a short piece of cable runs inside the cubby holes to the back of the radio above the PHside pilot berth. I used this system for 20 years but I never knew whether it was the best way to do it. I would love to know what my actual transmitted power level now is.
Tony Nield 'Dee Rover'