Can I fit a VHF aerial to the side of Al Mast

[Jcorstorphine]

I am completing a motorsailor project boat and need to relocate the aerial from the wheelhouse roof. I am reluctant to buy a new masthead aerial as I just bought the present Glomax unit about a year ago (before I decided to add the mast) Lack of forward thinking/ planning on my part.

Can I fit a bracket to the fwd side of the mast and mount the VHF aerial say about 2 m off the deck. It will clear the running rigging as it is all internal.

Also have the same question about the FM radio aerial. Is there any problem with having it close to the VHF aerial ( say 1 m higher, I am worried that when I am transmitting on VHF, I may couple into the FM aerial and scramble the electronics in my FM radio.

 

[john_morris_uk]

How big is the bracket that you are proposing? If the VHF antenna ends up being only a few centimetres or tens of centimetres away from the aluminium mast, then there will be some interaction and some effects that you might not want. It almost certainly won't blow anything up, but it might not work in all directions as well as you'd like. Can you really not get it to the top of the mast? There are all sorts of reasons why the top of the mast and in the clear is the best place. (increased range- lack of interaction with local metal work altering its effective impedance etc)

So long as the FM antenna is a few metres away from the VHF you should probably be OK. This is one case, where because FM signals are often strong, you can put the FM antenna lower down without too much concern.

 

[Jcorstorphine]

Can you really not get it to the top of the mast? There are all sorts of reasons why the top of the mast and in the clear is the best place. .

Thanks for reply.

The problem is that the present aerial is quite long (about 3 feet) and would look out of place at the top of the mast. I am also concerned that I would have to use a much longer coax as i got the impression from the Glomax data that it was designed to be installed with the fixed length of cable as supplied to ensure correct matching.

 

[V1701]

Attach to pushpit/guardrail at the back of the boat?

 

[st599]

Thanks for reply.

The problem is that the present aerial is quite long (about 3 feet) and would look out of place at the top of the mast. I am also concerned that I would have to use a much longer coax as i got the impression from the Glomax data that it was designed to be installed with the fixed length of cable as supplied to ensure correct matching.

But coupling to the mast will change the match anyway.

 

[john_morris_uk]

Thanks for reply.

The problem is that the present aerial is quite long (about 3 feet) and would look out of place at the top of the mast. I am also concerned that I would have to use a much longer coax as i got the impression from the Glomax data that it was designed to be installed with the fixed length of cable as supplied to ensure correct matching.

They are probably more concerned with the quality of joins in the cable than the length. If the antenna is matched properly, then the only disadvantage of long cable runs is the losses that result.

A 3 foot long antenna at the top of the mast shouldn't look out of place. Get a longer length of good quality coax fitted properly perhaps?

 

[prv]

The problem is that the present aerial is quite long (about 3 feet) and would look out of place at the top of the mast.

That's the norm on most boats I'd have thought (must admit I've never measured mine). Your aesthetics are your own, but have you noticed the "ugly" antennae on other boats?

Pete