David. I have some boats where the receiver wire alone is run horizontally in the ship under the deck/whatever and this works fine, but others seem to require a seperate ariel, mine are about 9 inches long normally…so I cut off 9″or receiver wire to compensate and keep the overall length the same.
It does seem to depend on how high the wire is off the surface of the water and also how far you want to go. As to how high the ariel has to be I dont know..as i say all mine are roughly the same length, but i am thinking that they could be a bit shorter to the same effect…
For your tug I should think you could hide an ariel in one of the funnels assuming it has some or even in a lighting mast, or EVEN it may simply need a little bit vertically in the superstructure. Suck it and see..the receiver wire can be lead inside a thin plastic tube to keep it straight and then you can experiment.
Tony as above says he never uses a seperate ariel, and this works for him.. I dare say others use a mix of do and dont
Ashley