Change Open to accessible for clarity... On 2/5/2013 10:19 AM, John Ferrell wrote: > A J-Pole does not require a ground. > Marine grade coax is expensive and stiff but lasts longer than any > other. If you can keep it out of harm's way and accessable for > inspection and replacement it will be best. The more likely source of > trouble is in the connectors. Even doing your best with the best you > should expect problems. If you can eliminate long cable runs it will > minimize problems. While manufacturers continue to refer to mil-spec > cables there is no such thing as mil-spec in regard to coax any more > that I am aware of. If the connections to the J-Pole are_ open_ (acces= sable) they may > be inspected. Any thing that permitted an antenna mismatch when > transmitting could have triggered an arc-over and a carbon trail in the > system especially in the antenna connection. An arc-over sometimes goes > unnoticed from storm activity. The radio, feed line and antenna can be > 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 var= iety 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 = the antenna cable in one of the boats. Might have been this one, I can't re= member. That one looked perfect until I got into the hull where the cable p= assed 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 earl= ier in the year. The antenna feeds a simple j-pole antenna. The 'earth' wil= l be via the radio ground to the motor. There is no provision in the antenn= a 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 an= d 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 cab= le. A cable in the elements can degrade much more quickly then one would as= sume, especially in the presence of sea water. Is it possible to carefully = inspect this cable over the whole run? Pay particular attention to corners = and 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 th= e outside, but after years of exposure started to let water in. The freeze/= thaw 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 lo= t 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 p= artially 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 a= bove the deck. >>> >>> I've not had the opportunity to look at it yet & expect to find connect= ion issues when I do, but it has been suggested that the immersion of the c= able 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 member= ship 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 .