VHF Antenna mounted to the roof or rail?

K

kevrangray

New member
Looking at getting my VHF antenna mounted but not sure if most of my fellow C-Dory brothers have their antenna mounted to the roof or to the rail? Any preferences...

Thanks,

Kevin
 
I have our 8' mounted on the side of the cabin near the helm side of the boat so I can lower it if need be from innside the boat. Plus we use a full winter cover and mounted on the roof we would have to remove it to install the cover. Ideally getting the antenna to the highest point is the best for reception. If a rail mount isn't going to get in the way it's less holes in the roof as water runs down hill.
D.D.
 
I don't like to penetrate the structure unless really necessary. I put a 3 foot whip on the starboard side on a small rail that I added when the Bimini went on. The rail is mounted to the cabin top overhang with big backup washers and the antenna has a nylon low profile ratchet mount around this rail. The coax runs into the cabin thru the back bulkhead up high under the cabin top lip. This is the only hole into the structure. This has worked out really well very easy to lower for trailering and great reception. Some folks worry about the low height of the antenna and it is true. The higher the better. However in the gulf islands and around BC if you call out the Coast Guard you get a 18 to 24 foot inflatable responder. They use 3 foot whips. I figure "good enough for them, good enough for me". George
 
I like having the antenna as high as possible. I mount it on the roof with a stainless steel ratchet mount. When I have to lower the antenna it means I'm also out there putting down the fenders.
 
Kevin-

Another option:

Mount the antennas on the forward brow so that the screw holes don't go through the roof into the interior, but are in the same very sturdy material, and the cable leads can go down and into the cabin up under the brow right next to the electronics shelf where the radio can be mounted.

Another good feature of this option is that the laid down antennas will fit conveniently right into the "grove" between the raised portions of the cabin top and the long handrails on both sides.

The only negative I'm aware of is that the antennas, when they're down, protrude into the area over the cockpit at about eye level. I offset this by placing antenna balls on their ends to blunt them. Union 76 petroleum here in California supplies the orange and blue balls for free at their stations.

Joe. :teeth :thup

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I have 2 VHF antennas mounted on the radar arch. One marine VHF and one 2M HAM radio. I would rather not penetrate the roof. I also used 6db Morad base loaded antennae that give you the full 6db without being 8 ft long. With VHF higher is better as it is line of sight.
HERE is a picture of two of them, there are also various lengths of base extensions you can mount them on. They are not cheap, but they perform well.
 
Kevin,

One of the things you might want to consider is if you are going to carry an inflatable on top or not. If so, will the antenna(s) be out of the way. I like that Joe's are forward, and don't penetrate the cabin roof, and lay close to the hand rail. Good positioning. I use a storage cover and the antenna really don't have any adverse affect on it. Mine were to close together to put an inflatable on the top, over the radar. I prefer the roof mount to the cabin side to have them out of the way from getting grabbed, and also (maybe) less salt spray corrosion.

Harvey
SleepyC :moon

IMGP1572.sized.jpg
 
Like SLEEPY Sea Angel has the VHF mounted outboard of the handrail on the roof. The SS rachet is reachable from inside the cabin from the helm seat. I won't tell you how often I overlooked raising the antenna after leaving the dock, but this setup does allow me to raise or lower it from inside the cabin.

I have found myself in a position where a bridge height was lower than I expected from the charts and tides. This setup has saved my antenna and me from the embarrassment of the OOPS.

My antenna also lays back over the cockpit, but the camper back keeps heads out of the way. Another use for the rachet is to leave the antenna elevated above the cabin roof a few inches so it doesn't rub or scratch it when lowered.

At some point I will add my second SS rachet for my 2Mtr radio in the same manner as SLEEPY; again so I can reach it.

Art
 
So why do you have two 8' antennas? One for each of two radios? Just curious...

Wandering Sagebrush":2txyhi63 said:
Kevin, I have 2 eight foot antennas. One on the radar arch, the other on the side of the house. Happy with both.
Click to expand...
 
Thanks for all the information. I will either be going with having the antenna attached to the rail or to the front part of the roof so that there is no hole above the cabin. Once again, thanks for all the info. I must say I really like the idea of a 6db w/o having to go the full 8 feet. This would allow me to place my cover (full boat cover) over the it w/o removing the antenna.

Kevin
 
Hi Kevin, something to keep in mind also, is that all vhf antennas are not created equal. The fibreglass 8 ft whips may look alike but it's what is inside that does the work. Economy whips have coaxial cable as the conductor, more expensive whips will have a combination of brass and copper tubes inside. The really expensive whips have a brass full length conductor. I have seen 8 ft economy whips not reach across the harbor here in Nanaimo. My 3 ft ss whips punch out just fine I've had chats with boats over 15 miles away . The coast guard aux here told me they switched to shorter 3 ft ss whips as they weren't breaking as often as longer whips. Although they go faster than c dorys usually. Also in many parts of the country, the Coast Guard will have repeater stations on high country so our line of sight gets much better. A good antenna can make an economy vhf radio perform well, and an economy antenna can make a good vhf perform poorly. Spend a bit more $ and get a middle or the road or better antenna and you should be pleased.
 
Also doen't think the higher the db rating the better the antenna. Mostly they come in 3, 6, and 9 db. The antenna may be 8 ft physically, but electrically it is much shorter. Think of the radiation pattern as a donut shape radiating out horizontally in all directions. Each of the above antenna will be putting out pretty much the same amount of power. A 3 db would look like a fat donut with a fairly broad radiation from water level upwards sort of like if you shined a flood lamp out. As you narrow the beam (6db) you are focusing the radio signal and it will travel farther. As you focus the beam to a spotlight and the narrowest (3db) the signal (or the light beam in the flashlight travels farther. Think of the 3db as more of a dinner plate shape. So why would anyone not want the 9db? Because when you have a narrow radiation pattern emmitting from your fixed boat antenna and you are on the water with no rocking and rolling it is fine. However when you are underway and the boat is rolling the narrow beam is moving up and down pointing down into the water or up way over the horizon and any receiver that might be able to receive your signal.
This is why for most small boats you do not want a 9db. If you are on a large vessel it is no where near the problem.
 
Anna Leigh":2cc8pf9n said:
Also doen't think the higher the db rating the better the antenna. Mostly they come in 3, 6, and 9 db. The antenna may be 8 ft physically, but electrically it is much shorter. Think of the radiation pattern as a donut shape radiating out horizontally in all directions. Each of the above antenna will be putting out pretty much the same amount of power. A 3 db would look like a fat donut with a fairly broad radiation from water level upwards sort of like if you shined a flood lamp out. As you narrow the beam (6db) you are focusing the radio signal and it will travel farther. As you focus the beam to a spotlight and the narrowest (3db) the signal (or the light beam in the flashlight travels farther. Think of the 3db as more of a dinner plate shape. So why would anyone not want the 9db? Because when you have a narrow radiation pattern emmitting from your fixed boat antenna and you are on the water with no rocking and rolling it is fine. However when you are underway and the boat is rolling the narrow beam is moving up and down pointing down into the water or up way over the horizon and any receiver that might be able to receive your signal.
This is why for most small boats you do not want a 9db. If you are on a large vessel it is no where near the problem.
Click to expand...

Very good description, I think? Trying to make heads and tails of this to cover most everything and cover the longest distance one should have a 6db?

This kind of explains what you were saying.
antennagain.jpg
 
Pat asked why some have two antennas. I have two because I have two radios--one is kept on channel 16, the other on the working channel of the area where I am boating, or the option of boat to boat such as channel 68.

You might ask would not a scanning radio work as well--and I say no. I had an experience a number of years ago--where a tug was giving a security call on channel 13, when I was giving security on 16--and visa versa==we both missed each other's calls, and ended up meeting in a very narrow stretch of waterway. I had to back down about 200 yards (not all that easy in a 62 foot single screw sailboat)--and lay my boat against a mud bank as the tug and barges crept by.

Another example would be in the PNW where there are many gill netters, and you need to find a safe path.

Also don't get hung up on the height. The difference between an antenna 6 feet off the water and 8 feet off the water is a transmission difference of one mile when looking at either the radio horizon of the ships radio, or the distance transmitting to and from a ship or land station with the antenna 40 feet off the water. For this example the C Dory antenna at 6 feet and the ship at 40 feet has a distance of 12 miles, with a C Dory antenna at 8 feet, this increases only to 13 miles.
 
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