Antenna cabling

[ctelfer38]

Advice from any technically knowledgable respondemts appreciated on the following. I am installing an AIS and have a redundant DECCA instrument cable running from the mast-top. With a new VHF aerial atop, will the old cable carry the VHF signal? Thanks

 

[Salty John]

The Decca cable is likely to be RG58 coaxial cable, but I'm not certain. This is usually 3/16" diameter. This cable is only suitable for very short runs on normal VHF applications. However, for AIS you are picking up a strong signal from a very elevated transmitter, so it will probably be OK. For AIS you don't need the antenna at the masthead anyway, so you could put an antenna on the rail with a short run of new cable.

 

[ctelfer38]

Thanks for that. The plan was to keep the clutter on the taffrail to a minimum; but I might need to live with it.
Charles

 

[john_morris_uk]

It depends on the condition of the cable. Co-ax that has had water ingress becomes very lossy very quickly. If you are confident in the cable and antenna, why not try it? You will soon see whether the AIS is picking up ships at a reasonable range, and you won't have lost anything.

 

[Talbot]

I have just installed a new 1.1m whip antenna (from http://www.jgtech.com/aerial.htm) It came with tinned aerial wire which Vtronix doesnt, and I installed it by my stern rail. From inside gosport, I was picking up a merch down by Nab at abt 12 miles on AIS using the NASA engine.

I would not want to put a receiving aerial close to a transmitting aerial at the mast head

I also have cross-over leads, so I can use the masthead on AIS and the stern rail as an emergency VHF aerial!

 

[Boatman]

Like the idea of cross-over leads can you give us more details?

 

[Talbot]

Very simple:

a trip to maplins for the following:

a pl259 female to male bnc 50 ohm adapter
This will connect to your VHF aerial and convert it so you can attach to the bnc 50 on the NASA engine.

Then make up a lead with a bit of spare VHF coax using:
a male pl259 plug at one end and a female bnc 50 atthe other end. connect the female BNC into the lead from the AIS aerial, and the pl259 into the VHF and you have an emergency aerial!