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  VHF Antenna for Center Console Boat with Bimini

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Author Topic:   VHF Antenna for Center Console Boat with Bimini
DaveS posted 01-23-2015 02:54 PM ET (US)   Profile for DaveS   Send Email to DaveS  
I'm going to install a VHF Marine Band radio in my 1999 Boston Whaler Outrage 17. I am looking for the right location to mount the antenna. I was thinking about [a short antenna] connected on the console railing. I had this setup on my old 1991 Outrage 17, and it worked well. But I have a bimini top on my new ride. I've never really used it, and it gets in the way more often than not, but I was hesitant to take it off. Any other suggestions?

Thanks and have a great weekend!

Dave

Ed Stone posted 01-23-2015 09:05 PM ET (US)     Profile for Ed Stone  Send Email to Ed Stone     
I also looked into the small antenna that mounts with a stainless bracket to the grab rail of the center console. If you are not traveling far offshore I would think the small antenna would be fine. Jimh has a article about the difference between the 3-foot antenna versus the 6-foot fiberglass. Of course, if you plan on going offshore past the sight of land, I would recommend the 6-foot mounted to the gunwale or the bow rail.
jimh posted 01-23-2015 11:49 PM ET (US)     Profile for jimh  Send Email to jimh     
See my discussion about antenna choice for a small boat in the article at

http://continuouswave.com/whaler/reference/VHFAntenna.html

The antenna I recommend is based on best radio performance. There is nothing about the recommended antenna that would make it less suitable for communicating long distances--the entire basis for choosing that antenna was to maximize communication range for a small boat. The suggestion that it is not suitable when "offshore" is not founded on any reasonable technical basis. It is entirely suited for "offshore" if that means for maximum communication range.

The antenna I recommend is also very suitable for "offshore" because of its durability.

The range of radio communication at VHF is primarily determined by the distance to the radio horizon from the antenna. The antenna length plays almost no part in the range. Antenna height above the sea is the primary factor in determining radio horizon distance.

Antennas only have a gain when comparing their signal strength in a favored direction to the signal strength in less favored directions. Since a small boat is in motion, antennas with narrow radiation patterns--or gain--may not be the best choice because the boat motion may deflect their main lobe of radiation away from the desired direction.

As for where to mount the base of the antenna on a small center console boat with a Bimini top, that is always a problem. Since the Bimini top covers the overhead of the center console area, having the Bimini top precludes mounting the antenna anywhere near or on the center console.

One must choose an alternate location for the antenna mounting base, somewhere along the gunwales of the boat. If angling for fish is important and you don't want the antenna to interfere with fishing rods and lines, the location on the gunwales can be chosen with that in mind.

If it were my boat, and because I am not an angler, I would mount the base of the antenna on the gunwale near the stern, with a base oriented so the antenna could fold down forward and lay on the gunwales.

If having a clear area aft of the center console for angling is important, then mount the base of the antenna mount on the gunwale forward of the center console.

jimh posted 01-24-2015 11:05 AM ET (US)     Profile for jimh  Send Email to jimh     
If the frame of the Bimini top of a center console boat is made of stainless steel tubing, the frame will be sufficiently strong to support an antenna mounting base for a VHF Marine Band radio antenna of light weight and compact construction. There is probably no VHF Marine Band antenna that combines such good performance with such light weight and compact size better than the GAM ELECTRONICS SS-2 antenna that I recommend. It ought to be possible to use a rail-mount clamp-on mounting base to attach to the frame of the Bimini top. The SS-2 antenna could attach to such a base. Such a configuration would be an excellent solution to mounting an antenna on a small boat with a center console and Bimini top. The antenna base would be elevated nicely, and the antenna would be completely out of the way for any sort of angling with rods and line.

I have thought about mounting a VHF Marine Band radio antenna on the frame of the Flying Top of my boat, but, because I also have side curtains and a windshield that zipper onto the Flying Top, an antenna base on the frame would interfere with the rest of the weather canvas system. On a center console boat the weather canvas usually does not include side curtains, so mounting the antenna base on the frame would not create any problem.

It would also be possible to drill holes in the frame tube and run the transmission line for the antenna inside the frame tube. The transmission line would have to exit the frame tube at the bottom, near the pivot point. If the canvas top is to be removed, a connector could be installed on the transmission line there, so the canvas and frame could be removed.

The clamp-on base would need to be chosen to work with the canvas top frame tube diameter, but I think that should not be much of an obstacle. Some of the clamp-on antenna base designs allow for the angle of the antenna to be set with a set-screw adjustment. That would make a compact antenna mount, smaller than the typical ones with a level adjustment for tilt-down of the antenna. If you had to lower the antenna to get under a bridge, you could just lower whole canvas top. Also, I think the antenna would stow reasonably well with the canvas top tilted down to the gunwales.

jimh posted 01-24-2015 11:10 AM ET (US)     Profile for jimh  Send Email to jimh     
A suitable rail mount base for the GAM SS-2 antenna is shown at

http://shakespeare-marine.com/style-4720

The long screws that supply compression to the rail clamp could be cut to length, making for an attractive installation.

saumon posted 01-24-2015 11:58 AM ET (US)     Profile for saumon  Send Email to saumon     
In the case of a bimini frame mounted antenna, a problem I see is how would one use the antenna when the top is folded down?

As an alternate solution, I know of a couple of persons who had a canvas shop made a 6" cut with reinforcment and a velcro flap. They mounted the antenna to the console grab rail and, when the top is in use, they simply open the flap and pass the antenna through the straight cut by slightly bending it.

jimh posted 01-25-2015 12:28 AM ET (US)     Profile for jimh  Send Email to jimh     
Usually on a small boat with a Bimini top, when the top is not fully deployed, its frame is still erected. The whole frame is usually not folded down to the gunwales. If it were, it would get in the way. If the antenna base were mounted to the part of the Bimini top frame that remained in position when the canvas was stowed but the frame was still up, the antenna would not be affected.
saumon posted 01-25-2015 05:20 AM ET (US)     Profile for saumon  Send Email to saumon     
quote:
jimh posted 01-25-2015 12:28 AM ET (US)
--------------------------------------------------------------------------------
Usually on a small boat with a Bimini top, when the top is not fully deployed, its frame is still erected. The whole frame is usually not folded down to the gunwales.

That must be a regional thing and could be different for boats of 20 ft. or longer, but in my area for boats under 20 ft., the version of the Bimini top that completely fold down on the gunnels, either toward the front or the back, is seen 75% of the time. The other version, that stay erect when not deployed and need an additional support leg toward the back, is a major annoyance and is always in the way, be it for jumping on or off the boat. When there's any kind of fishing involved, the prevalence of the folded down version reach 100%.

jimh posted 01-25-2015 07:46 AM ET (US)     Profile for jimh  Send Email to jimh     
I imagine that what determines if a Bimini top is stowed in a lowered position or left in a raised position with fixed support arm probably depends on how well it stows when lowered. If it folds forward and out of the way of the aft cockpit, it wouldn't interfere with much angling action. On a 17-foot center console boat I'd think that a lowered Bimini that was folded to the stern would be right in the way of all the prime space for rods and lines.

Cutting a little access hole in the Bimini top for the metal whip of a radio antenna to poke through could be an option, but only if you have a good canvas maker around to cut that opening. I wouldn't want to take a pair of scissors to my Wm. J. Mills & Co. Flying Top to make a hole for a radio antenna. And I wouldn't recommend it.

saumon posted 01-25-2015 08:45 AM ET (US)     Profile for saumon  Send Email to saumon     
Exactly. On my 1991 Outrage 17, the Mills Bimini top fold forward on sliding tracks and is stowed against the bow rail, completely out of the way:

http://www.myfishingpictures.com/data/500/Outrage.jpg
(obviously, the top can't be used when the fishing rods were in the console rod holders!)

The setup I was talking is like this one, without any hole, or with the antenna a feet and a half higher but with an opening in the top. I'm not sure, too, that the gain from the slightly higher location is worth cutting the top.

http://www.onewolf.org/images/tw18.jpg

Phil T posted 01-26-2015 11:13 AM ET (US)     Profile for Phil T  Send Email to Phil T     
Dave--I moved my antenna to the stern quarter using a rail mount. It was out of the way and not used as a grab rail. It stowed on the gunnel. It allowed full use of the bimini. It would need to be stowed when fishing off the stern.

DaveS posted 01-26-2015 07:32 PM ET (US)     Profile for DaveS  Send Email to DaveS     
Thanks for all the info. I have lots to think about. [Changed topic; the new topic is now its own thread--jimh]
contender posted 02-02-2015 05:44 PM ET (US)     Profile for contender  Send Email to contender     
I used a stainless METZ-brand antenna mounted to my console. It fits under the bimini top, but it is removable and can bend a little.
jimh posted 02-03-2015 09:41 AM ET (US)     Profile for jimh  Send Email to jimh     
The METZ VHF antenna mentioned above is probably the MANTA-6 VHF Marine Antenna. It is designed for mounting with an L-bracket mount. The METZ VHF antenna has a connector which needs a PL-259 to mate with. It is not supplied with a transmission line. For installation you have to purchase transmission line and install two PL-259 connectors.

The METZ antenna is similar to the GAM ELECTRONICS SS-2 antenna; both are base-fed half-wave radiators using a stainless steel radiating element.

I prefer the GAM ELECTRONICS SS-2 antennas due to the wider variety of mounting available for it. The ADAP-II base provide a very nice method for mounting to the standard 1 x 14 threaded mounting, and includes about 15-feet of transmission line using RG-58C/U, the highest grade of coaxial transmission line available.

For mounting atop a sailboat mast and connecting to the antenna with a long run of 0.5-inch-diameter transmission line, the METZ MANTA-6 VHF Marine Antenna is a good choice. Note that the GAM ELECTRONICS SS-2 antenna can also be mounted on an L-bracket and can connect directly to a PL-259.

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