A J-Pole does not require a ground. Marine grade coax is expensive and stiff but lasts longer than any=20 other. If you can keep it out of harm's way and accessable for=20 inspection and replacement it will be best. The more likely source of=20 trouble is in the connectors. Even doing your best with the best you=20 should expect problems. If you can eliminate long cable runs it will=20 minimize problems. While manufacturers continue to refer to mil-spec=20 cables there is no such thing as mil-spec in regard to coax any more=20 that I am aware of. If the connections to the J-Pole are open they may=20 be inspected. Any thing that permitted an antenna mismatch when=20 transmitting could have triggered an arc-over and a carbon trail in the=20 system especially in the antenna connection. An arc-over sometimes goes=20 unnoticed from storm activity. The radio, feed line and antenna can be=20 evaluated independently IF you can gain access to them. What do you mean when you say "transmission issues?" On 2/4/2013 11:41 AM, Joe McCauley wrote: > Thanks folks, you all confirm what I told the guys here. To answer a vari= ety of questions, It did work satisfactorily, but I must say we are always = having problems with the electronics in these boats. Last year I replaced t= he antenna cable in one of the boats. Might have been this one, I can't rem= ember. That one looked perfect until I got into the hull where the cable pa= ssed the fuel tank. It was practically rotten in there over a meter length.= I suspect fuel got spilled on it as we had issues with the fuel tank earli= er in the year. The antenna feeds a simple j-pole antenna. The 'earth' will= be via the radio ground to the motor. There is no provision in the antenna= mount for an earth there. > > I'm pretty sure I'll find cable/connection or maybe radio problems when I= get to look it over. > > Joe > > -----Original Message----- > From: piclist-bounces@MIT.EDU [mailto:piclist-bounces@MIT.EDU] On Behalf = Of Herbert Graf > Sent: 04 February 2013 15:13 > To: Microcontroller discussion list - Public. > Subject: Re: [EE] Marine VHF radio antenna cable and seawater > > In a perfect situation you'd not notice any issues, a properly sealed and= shielded cable won't mind whether it's awash or not. > > That said, if you are having problems, I've no doubt it could be the cabl= e. A cable in the elements can degrade much more quickly then one would ass= ume, especially in the presence of sea water. Is it possible to carefully i= nspect this cable over the whole run? Pay particular attention to corners a= nd where the cable mounts hold it. It's entirely likely that a small crack = or hole has formed letting water in. > > Also have a good look at the ends, look for signs of corrosion. I've had = many cases where a properly weather sealed end looked perfectly fine on the= outside, but after years of exposure started to let water in. The freeze/t= haw cycle can breach even the highest quality connectors. > > TTYL > > On Mon, 2013-02-04 at 14:21 +0000, Joe McCauley wrote: >> This may not be the most appropriate forum for this, but there are a lot= of knowledgeable people here.... >> >> Does anyone have any thoughts on what the effect on transmission >> efficiency would be of the antenna feed cable for a marine VHF radio >> being partly submerged in seawater. (f~160MHz) >> >> The cable on my scuba club's boat runs along the deck which is always pa= rtially awash. This is the way it was built. Apart from that reason, I don'= t think that the cable being immersed should cause significant issues. We = are having radio transmission issues. The antenna is mounted ~1.5 meters ab= ove the deck. >> >> I've not had the opportunity to look at it yet & expect to find connecti= on issues when I do, but it has been suggested that the immersion of the ca= ble could be causing our problem. As I said, I don't believe that, but.....= ... >> >> Thanks for any info, >> >> Joe >> > > -- > http://www.piclist.com PIC/SX FAQ & list archive View/change your members= hip options at http://mailman.mit.edu/mailman/listinfo/piclist > > > --=20 John Ferrell W8CCW That which can be destroyed by the truth should be. P.C. HODGELL =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .