Association Forum - Coaxial cable

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Coaxial cable

New Topic

Topic Locked

Printer Friendly

Author

Topic

Waterboy
Navigator

Member Avatar

USA
204 Posts

Initially Posted - 05/08/2004 : 16:20:30

Hey radioheads! I's like to mount my VHF antenna atop the mast (very best location, right?) and have a few questions:

- what's the best type of coax to use considering weight aloft, cost, and signal loss along the length of the cable? The stuff varies in cost from a little over $0.10/ft for Home Depot stuff to almost $6/ft for Shakespeare's Lo-Max. The specs show many different 'RG' types as well as impedence, capacitance, and velocity ??? What do I realistically need for very good transmission and reception?

- once I have the cable pulled through the mast, what's the best way to get it out the bottom? Ie; drill a new hole in the bottom of the mast?

- how have you run the cable from the mast step area to the radio (usually mounted just inside the companionway to starboard)?

As always, thanks in advance !!

Greg

Edited by - on

frog0911
Master Marine Consultant

Members Avatar

USA
1349 Posts

Response Posted - 05/09/2004 : 14:10:56

Greg, the cable I used is the same that is used for satellite dish installations. I was looking for RG-59 cable and was rocked by the prices when a ham operator friend told me I should use the same as the they are using which is RG-6. He said it too is expensive if bought of the roll. He said to go to Radio Shack and get a DIY satellite kit. The one I got was a DKIT96. It comes with 100 feet of RG-6 with attached ground, but you can pull the ground off. The kit cost was $29.95 and has a lot of other stuff you might be able to use in your media room. I could not get the cable alone for close to that price, as I'm sure you found out. Attached are some pictures of how my cable entered, exited the mast and went through the hull. Since I don't trailer the boat I ran the cable continueous to the radio through the deck.

Once in the boat you can find your way back along the side under the windows in a C25.
Installing the cable in the mast is much, much, much easier if the mast is off the boat. Good luck with your install.

Edited by - on

Waterboy
Navigator

Members Avatar

USA
204 Posts

Response Posted - 05/10/2004 : 11:51:32

Thanks Frog! The photos are quite helpful. I should have mentioned I've a 250 rather than a 25. Anyone know how hard it is to snake wiring back between the liner and deck in a 250?

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 05/10/2004 : 19:08:08

First, needed is 50 ohm cable not 70 ohm TV coax. I'd use RG 58 over RG 8 because of weight even though some increase in signal loss will result. Of course there are coax styles between these two which will trade weight for signal strength. The lengths involved aren't critical with RG 58.

I'd look hard at a Shakespere 5/8 rail mounted whip compared to a mast mounted. Much easier to mount and it doesn't provide a lightning rod, unless the maximum of performance is needed....then of course, the mast head antenna is best.

Edited by - on

frog0911
Master Marine Consultant

Members Avatar

USA
1349 Posts

Response Posted - 05/11/2004 : 00:11:21

Snaking the wire back on the starboard side isn't that difficult, but you need one special tool called a electrican's snake to make the job easier. I removed the teak molding from the side to prevent the cable from getting hooked on a screw as I pulled it back. To get it through the liner just remove the starboard high intensity light and go to the starboard side of the boat and push the snake up under were the teak molding screws in, toward the light. Once you see it attach a nylon string and pull it back. Pull out enough string to reach the switch panel plus about three feet. Then go to the switch panel and push your snake forward until it comes out were your string is hanging. Attach your string and pull it back to the switch panel, leaving about two to three feet at the starboard exit point. Pull all your cable into the boat through the light opening, then pull it all to the starboard side with you string and last pull it back to the switch panel. Once you have it there you can pull it tight and it will raise up into the void between the hulls. Then reinstall the teak molding and the light and your all set.
One other thing, my mast has a tube in it and Catalina had put a pull string in it so you can use that to pull the cable through the mast. You will have to take off the mast foot by drilling out the rivets so you can pull it all the way through. After you get the cable out the side of the mast you can reinstall the foot with rivets or screws. I use # 12 stainless sheet metal screws coated with vaseline to reduce the chance of corrision.
I don't know what the ohm rating is on the RG-6 cable, but I use to be in the satellite installation business and the cable we used for antenna to house was 50 ohm RG-59U. In the house we use standard 70 ohm TV coax. I would not have use RG-6 either except for the fact that a good friend, who is a diehard HAM operator, recommended it. So far it has preformed well and the impedence match is 1:1.15 which is almost perfect (1:1).
Just take your time amd you should have no problems.

Edited by - on

Waterboy
Navigator

Members Avatar

USA
204 Posts

Response Posted - 05/11/2004 : 13:06:57

Thanks heaps guys - great info. Arlyn, you bring up an additional point I've been quite concerned with: lightning. <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I'd look hard ... at a ... rail mounted whip ... it doesn't provide a lightning rod<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> Now I just reread the 'Lightning and Sailboats' thread as well as your article on the same subject, and am perusing Ewen Thomson's article. Of course I'm confused as well as concerned, and want to take the most prudent overall course of action. My thinking has been essentially this:

1) A VHF antenna mounted atop the mast would provide much greater transmission range in the event of an emergency.

2) Any increase in the lightning 'attractiveness' due to the additional ~4' height would be minimal, especially because: <blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">If the mast is not grounded, it makes little difference whether there is a Metz, Windex or an ion brush on top.(from Arlyn in 'Lightning and Sailboats' thread)<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I think this 250WB is about as ungrounded as can get; I certainly don't have anything intentionally providing a ground. My outboard has no connection to the ship's electrical system ... I suppose the speed sensor and depth transducer could provide a ground (?)... then there's the copper in the bottom paint, too.

Incidentally, the boat already has a 5/8 rail mounted whip, but with the antenna base only about three feet off the water, I assumed the range would be pretty short, and that raising the antenna a good 25'+ would likely more than double my range - very valuable in an emergency (there's no real way I can test this in AZ on the hard). But if the mast top antenna will significantly increase the liklihood of a lightning strike, perhaps it isn't worth it. It'd certainly save me $$ and #$@%& given that there's a rail mount already in place.

Again let me express my appreciation for the input and feedback. While, IMHO, my mama din't raise no dummy, I am a novice in this area. The First Mate and I are planning a summer's worth of trailer sailing, and I'm trying to get everything just right (or as close as possible) before we go.

Edited by - on

svmoxie
Past Commodore

Members Avatar

USA
331 Posts

Response Posted - 05/11/2004 : 20:03:04

FYI There is an excellent article on lightning and boats in the May Mainsheet not to mention a wonderful article from Leon on his Bahamas trip.

IMHO - if your on an inland fresh water lake, bonding / grounding isn't going to do you a lot of good. At the same time you don't necessarily need the maximum range that a mast head antenna would give you. Depending on your sailing area you might be better served with a good hand held vhf.

If you go with the masthead be sure that you use a sailboat antenna. If you use the stern rail mount you can use either style.

My choice was for a metz at the masthead with RG58 cable and an unbonded / ungrounded boat.

Edited by - on

Gloss
Master Marine Consultant

Members Avatar

USA
1916 Posts

Response Posted - 05/11/2004 : 21:57:03

Hi there,
I recently installed a mast mounted Shakespeare whip antenna with 3 db gain. I used the Shakespeare gold plated centerpic connectors. I used Ancor wire as it is tinned and marine rated. I believe I used RG8x.
The system worked great on my trip to the Keys last February. I don't use my VHF on my local lake.
I also installed a Shakespeare splitter to go to the FM stereo too. It really pulls in the stations.
Good luck.
I believe that there is some importance to using tinned wire, especially if you are in salt water, and also not to use residential wiring, something about OHMs or some such technical stuff.
I also greased all of my connections with dielectric grease too. and put shrink wrap on the exterior connectors, where it meets the wire.

Edited by - on

frog0911
Master Marine Consultant

Members Avatar

USA
1349 Posts

Response Posted - 05/11/2004 : 23:48:34

Frank, brings up a good point I forgot to mention, that of water intrusion. The fix is have as small a number of splices you can get by with and, as Frank stated coat each with a dielectric grease and then seal. I used a dielectric tape form Radio Shack. Regular black electrical tape will over time allow water to weap into the connector. I also agree with the tined wire theory except the if you use dish antenna cable it is design to be buried and is suppose to last 50 years underground. Again stay away from internal house coax for any external use as has been mentioned in other responses.

Edited by - on

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.