Antenna Mount for Center Console with Bimini Top

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
roundle1979
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Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Sat Nov 21, 2020 9:16 am

[Moved to VHF MARINE RADIO forum for discussion.]

I am planning to install a fixed mount VHF--perhaps a Standard Horizon GX1400--in my 2004 Boston Whaler Nantucket 190 center console.

Standard Horizon is recommending a 2.5 meter, 6 dB antenna. Where should this Antenna be mounted?

Keep in mind the following:

--I like to keep my bimini top deployed 100% of the time, and
--I have young kids who like to swing from anything they can get their hands on.

Thanks.

Jefecinco
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Re: Antenna Mount for Center Console with Bimini Top

Postby Jefecinco » Sat Nov 21, 2020 9:34 am

I would look for a convenient location in the aft most part of the cockpit. A problem with locating antennas far from the console is routing of the antenna cable. You don't want the cable on the deck. If you mount it aft you may be able to find a way to route the cable down into the rigging tube and run it up into the console then to the radio. If you surface mount the radio the cable connection can be made inside the console thus providing a nice sanitary looking installation. I recommend a ratchet mount antenna base so the antenna can be lowered when the boat is trailered.
Butch

jimh
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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Sat Nov 21, 2020 12:08 pm

roundle1979 wrote:Where should this Antenna be mounted?


Generally you cannot mount a VHF Marine Band radio antenna to a center console if there will always be a Bimini top deployed above the console. This rules out mounting the antenna to the console.

With the console not an option for mounting the base of the antenna, about all that is left is to mount the antenna base on a gunwale. Chose a location on the gunwale that will allow the antenna to be folded down (using a ratchet mount) and lie atop the gunwale in some manner where it won't interfere with railings or cleats or other attachments to the gunwale.

The transmission line that connects the radio to the antenna must be run in some manner that avoids having the transmission line run across an open deck. Typically there will be rigging tunnels or other access paths that permit this to occur.

Another consideration for antenna location is the use of the boat for angling. Many anglers to not want any tall structures mounted at the boat stern because they would interfere with fishing lines. If you are not an angler, consider mounting the antenna base at the stern on the gunwale. The antenna can be folded down in the forward direction if necessary to allow bettering access to the stern for angling, if desired.

A final possibility is to use a rail-mount base and mount the antenna base to the tubular frame of the Bimini top. In that location a 3-foot metal whip-type antenna could be installed on the base without an extension mast. Routing the transmission line may be more difficult.

ASIDE ON RECOMMENDED ANTENNA TYPE: I don't recommend using a fiberglass-encased 8-foot long antenna. The fiberglass radome is fragile and easily broken. The 8-foot antenna is not particularly the best choice for a small boat that will be rocking in waves.

For more than a decade I have used an 3-foot metal whip antenna mounted atop an extension mast. The metal whip antenna is very resilient and won't break easily. For details see the REFERENCE article at

VHF Marine Band Antennas For Small Boats
http://continuouswave.com/whaler/reference/VHFAntenna.html

More about recommended antennas at

VHF Marine Band Radio Antenna Recommendation
viewtopic.php?f=13&t=5938

roundle1979
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Re: Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Sun Nov 22, 2020 8:44 am

antennaPositionCenterConsole.jpg
Fig. 1. A VHF Marine Band antenna mounted to the console of a 190 NANTUCKET.
antennaPositionCenterConsole.jpg (15.18 KiB) Viewed 426 times


As seen above in Figure 1, when the Bimini top is deployed the antenna remains forward of the top. I am going to try something like this.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Sun Nov 22, 2020 10:21 am

The antenna position seen above in Figure 1 is not a good solution--actually it is an awful location for the antenna to be mounted. There are many problems:

  1. the metal radiating element is exposed and could easily be grabbed by a crew person
  2. the antenna height is insufficient for good performance
  3. the antenna is too close to the GNSS receiving antenna also mounted on the console
  4. the antenna is too close to other electronics on the console
  5. the antenna is surrounded by metal conductors in the console railing and bimini top frame
  6. the antenna is too close to the transmitter it connects to.

A far better solution, assuming that the forward edge of the Bimini top is aft of the forward edge of the center console--which sounds rather odd but is described as such for the installation shown--would be to mount a 4-foot extension mast on the console in about the location seen in Figure 1, and then mount a 3-foot metal whip antenna to the extension mast. That mounting corrects all the errors I mention in the proposed mounting.

For me, the most important safety device on the boat is the VHF Marine Band radio. It provides essential radio communication to the Coast Guard and to other boats. For that reason, its antenna should be mounted as advantageously as possible.

You asked for advice, so I have offered my comments on your proposed antenna location.

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Phil T
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Re: Antenna Mount for Center Console with Bimini Top

Postby Phil T » Sun Nov 22, 2020 12:31 pm

If you will deploy the bimini or store it vertically, mounting a whip on the bimini frame with a ratchet mount and stand-off bracket is a practical solution.

You can disconnect the transmission line from the antenna base for the times you need to stow the bimini flat, as when trailering.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

roundle1979
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Re: Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Tue Nov 24, 2020 8:50 pm

Appreciate the input so far.

For reference, below is a photo of Boston Whaler's factory antenna mounting location on the 190 NANTUCKET.

Nantucket Antenna 2.png
Fig. 2. Antenna mount location on 190 NANTUCKET.
Nantucket Antenna 2.png (154.73 KiB) Viewed 292 times

jimh
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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Tue Nov 24, 2020 11:49 pm

I don't see the antenna in the photo. Unless it is pointing downward. Is this a joke?

roundle1979
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Re: Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Wed Nov 25, 2020 10:12 am

It's mounted on the right hand side of the console's handrail. Indeed, pointed down.

Jefecinco
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Re: Antenna Mount for Center Console with Bimini Top

Postby Jefecinco » Wed Nov 25, 2020 10:18 am

{The antenna shown in Figure 2] is not a Boston Whaler factory mounted antenna.
Butch

roundle1979
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Re: Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Wed Nov 25, 2020 11:35 am

Jefecinco wrote:{The antenna shown in Figure 2] is not a Boston Whaler factory mounted antenna.
I think you are correct. I just got off the phone with Boston Whaler. Here is a drawing for a 2020 Outrage 190 when option 100 2254 [VHF RADIO] is selected:

BW Outrage 190 Antenna .png
Fig. 3. Boston Whaler drawing showing installation of a VHF Marine Band antenna on the center console.
BW Outrage 190 Antenna .png (94.83 KiB) Viewed 269 times


Compare at: http://bostonwhaler.com.s3.amazonaws.co ... e-2012.pdf

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Thu Nov 26, 2020 10:15 am

ROUNDLE'--thank you for researching and finding the OEM drawing. Having good information like that is very useful and much appreciated.

Notwithstanding that Boston Whaler mounts the VHF Marine Band antenna as shown above in Figure 3, the location of the antenna is still not particularly good, as it has all the same problems I listed earlier.

The problem of where to mount a VHF Marine Band radio antenna on a small center console boat that has a Bimini top that can fold down when not in use and the top creates an overhead obstruction in the console area is not confined to a particular model of Boston Whaler boat; it is really a universal problem with all small center console boats with Bimini tops.

Whether the boat owner is willing to accept all the compromises of a bare metal whip antenna being mount right at the center console is an individual decision. As I stated earlier, in my opinion the VHF Marine Band radio is a primary safety device on a boat, and the choice of the antenna location should be made with that in mind. Also, using the VHF Marine Band radio to transmit must also be considered in regard to any possible interference with other electronic devices. Having the radiating element of the antenna just a few inches away from the radio itself or from other electronic devices is clearly not recommended. Generally the manufacturers of VHF Marine Band radios recommend a three-foot separation of the transmitter and the antenna, and that is best if the three-foot separation is in the vertical plane.

I just can't endorse the mounting location illustrated in Figure 3; there should be a better option.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Thu Nov 26, 2020 10:49 am

Since I have been critical of the antenna mounting location illustrated in Figure 3, I have a burden to offer an alternative. In giving some thought to a solution to the problem under discussion here, an idea occurred to me. I will describe a possible solution.

In order to provide for the VHF Marine Band antenna to be able to clear the obstruction of the Bimini top above the console, the antenna should be mounted atop an extension mast. The antenna should be a lightweight 3-foot metal whip antenna, and for that type I prefer the GAM ELECTRONICS SS-2 antenna because of its superior mounting options. The extension mast will mount to a ratchet base on the center console. The base can be located as shown in Figure 3, put perhaps mounted a bit farther forward.

Now for the unusual aspect of my proposed solution: the extension mast will not be a straight tube. The extension mast will have a bend, a dog-leg. The orientation of the extension mast at the ratchet mount on the console will be adjusted so the mast projects upward and also forward, with the angle being selected so that the mast clears the front edge of the Bimini top when the top is either in use or in the stowed position (if stowed forward). Then a slight bend in the extension mast will be necessary to create a true vertical extension of the mast.

There will not be an off-the-shelf extension mast available with the proper length and bend, so the mast will have to be fabricated. One possible method might be to buy a existing 4-foot metal tube mast and bend it. This could be a problem because the typical mast is made from stainless steel tubing and could be difficult to bend using a conduit bender.

antennaMountBentMast.jpg
Fig. 4. A concept for mounting an antenna on a center console and using a bent extension mast to clear the Bimini top.
antennaMountBentMast.jpg (13.07 KiB) Viewed 215 times


If a lightweight antenna is used, and a heavy-duty ratchet mount used at the base, the ratchet mount should be able to hold the bent extension mast and antenna in position without difficulty. The amount of forward tilt needed will depend on the particular Bimini top in place. The forward tilt may not be too great as it was mentioned that the Bimini top did not extend too far forward beyond the center console forward edge.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Thu Nov 26, 2020 11:11 am

A variation on the idea shown in Figure 4 might be to use 1-inch stainless tube as employed in making the railings, along with some fittings to attach a rail hinge and a tube end hinge. An extension could be added to the console railing, angling upward so it clears the Bimini top forward edge. Then a rail-mount antenna base could be attached and set at the proper angle. The antenna then mounted to the rail base. This could be done from the center line of the console, adjacent to the exiting center support tube. A second new railing would be used to hold the first railing in a fixed position.

The rail mount would be something similar to the Shakespeare Economy Rail Antenna Mount (4720)

The antenna transmission line could be fed down the tubing. The open upper end could be dressed with a press-fit plastic cap with a hole drilled for the transmission to pass through.

This arrangement would permanent rigging, so it would not be easy to lower the antenna for travel on the highway.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Thu Nov 26, 2020 11:31 am

With more thought comes an even simpler solution:

Rather than bend the extension mast, just use a straight extension mast. A four-foot mast may be about the right length. Mount the GAM SS-2 antenna to the extension mast with the GAM ADAP-II mount. To correct for the antenna whip being oriented at an angle from vertical, just make a small bend in the steel whip itself just above the transformer coil to correct for the angle of the mount.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Fri Nov 27, 2020 6:12 am

I notice in the drawing (Figure 3 above) the railing around the console has a center support rail that goes downward. In the photo illustrations (Figures 1 and 2 above) there is no center support railing at the console. Which is a more accurate representation of the actual center console under discussion in this thread?

roundle1979
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Re: Antenna Mount for Center Console with Bimini Top

Postby roundle1979 » Sun Nov 29, 2020 9:22 am

jimh wrote:With more thought comes an even simpler solution:

Rather than bend the extension mast, just use a straight extension mast. A four-foot mast may be about the right length. Mount the GAM SS-2 antenna to the extension mast with the GAM ADAP-II mount. To correct for the antenna whip being oriented at an angle from vertical, just make a small bend in the steel whip itself just above the transformer coil to correct for the angle of the mount.


Certainly appreciate the insight.

I will probably go with the factory antenna position on the console. As I am in Long Island Sound (and rarely more than 2.5 miles from any shore), I believe the setup is adequate (and an improvement over my current handheld). If I were offshore or in a remote area (like Maine) I would probably go with a mast-like solution like you have suggested.

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Re: Antenna Mount for Center Console with Bimini Top

Postby jimh » Sun Nov 29, 2020 9:27 am

If you reduce the VHF Marine Band radio transmitter power to 1-Watt from 25-Watt, the potential for the radio signal to interfere with other electronic devices located close to the antenna will be greatly reduced, and if your range to shore is less than 2.5-miles, a transmitter power of 1-Watt will be sufficient to contact the RESCUE-21 U.S. Coast Guard radio watch stander in the event of any problems.

Transmitting at only 1-Watt will also reduce your exposure to radio-frequency energy coming off the antenna, as the top of the antenna will be just about at your eye level. In most instances of recreational boating and VHF Marine Band radios, the radio is in the receive mode about 99.9-percent of the time, so your exposure will be very minimal, even though the antenna is extremely close to you.

Because a metal whip antenna represents a hazard when transmitting if accidentally touched by a person, you should check before keying the transmitter that no one is near the antenna. Burns created by radio-frequency energy tend to be deep burns. I have had one, and it took a long time to heal.