VHF Marine Band Antenna for Small Boats

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
jimh
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VHF Marine Band Antenna for Small Boats

Postby jimh » Fri Feb 05, 2016 9:27 am

About ten years ago I installed a new VHF Marine Band antenna on my 22-foot Boston Whaler boat. I wrote an article describing in detail the installation and explaining why I chose the various components. Inasmuch as the ten-year-old original components are still working perfectly and show no signs of any wear or damage, I do not have any plans to change my antenna installation. I am very pleased with the durability of this antenna system, and also with its performance as a radio antenna.

I recently updated the article to include information on the present day prices of all the components. Thanks to substantial discount pricing from a large on-line distributor, the cost to buy the three components of the antenna system is still quite reasonable and totals just $115. The three components of the antenna system are:

--a half-wave end-fed radiator with matching coil by GAM ELECTRONICS, model SS-2, about $50;

--a special mounting adaptor with integral coaxial transmission line by GAM ELECTRONICS, model ADAP-II, about $25; and

--a four-foot polycarbonate extension mast by SHAKESPEARE, model 498, about $40.

This new thread has been created to alert readers to the update and to provide a thread for any on-going discussion or questions about the antenna installation. (A similar thread in our old forum can no longer accept new postings.) I will monitor this new thread and will be glad to answer any questions related to the article. The article has also been updated to point to this new thread as the proper place for inquiries or comments (and to fix some minor errors in the HTML and restore navigation links). The article still appears at the same URL as it has since its initial publication:

VHF Marine Band Antennas For Small Boats
http://continuouswave.com/whaler/refere ... tenna.html

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A 3-foot metal whip with base coil mounted on a tall extension mast makes a great antenna for a small boat. Photo credit Don McIntyre
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nautiwhaler32
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Re: VHF Marine Band Antenna for Small Boats

Postby nautiwhaler32 » Mon May 16, 2016 1:05 pm

Would it be possible to trade out the four-foot polycarbonate extension mast by SHAKESPEARE for
the Shakespeare 5228-2 2 foot Galaxy® Extension Mast? Thanks--Matt
1996 Outrage 17 -Red Bank, NJ

jimh
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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Mon May 16, 2016 7:01 pm

You can use a 2-foot extension mast in place of a 4-foot extension mast if that suits your application better. You just lose some antenna height. Higher is always better.

toniintc
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Re: VHF Marine Band Antenna for Small Boats

Postby toniintc » Tue May 17, 2016 11:59 am

Thanks for the effort in this article, it was a GREAT help. I did some Google searches for the best antenna for a small boat and hit on your article. It sounded perfect for my 23' boat, so I ordered all the parts yesterday. I'll post back a photo when I'm done. (Coincidentally, I'm in Traverse City by the way)

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Tue May 17, 2016 1:16 pm

I was in Traverse City on Sunday morning--it was snowing. I think it will warm up this week, so by the time you get the antenna components the weather will be warm enough to install them. Thank you for the kind words about my article on antennas.

The antenna I recommend is a good performer, and the detail of the connection of the antenna base to the actual antenna, with the integral transmission line, makes for a very neat installation. The antenna, the mount, and the polycarbonate extension mast are all very durable. They just last and last.

Many articles seeking advice about a new antenna begin with a comment like this: "I hit some obstruction with my existing antenna and the fragile fiberglass encased whip section shattered..." You won't have that problem with the GAM SS-2 steel whip.

toniintc
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Re: VHF Marine Band Antenna for Small Boats

Postby toniintc » Thu May 19, 2016 6:09 pm

I received most of what I need today. The ADAP-II is different than what you show. The biggest concern with it is that the antenna will only thread into it about two turns because the receiving threads are way down in. The ADAP-II will need to be shortened so it can fully thread in. [There is actually no problem; see further explanation below--jimh]
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jimh
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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Thu May 19, 2016 7:22 pm

Contact GAM ANTENNAS to get advice. The ADAP-II looks like it is longer than the original one I got years ago. Give them a call to see what they have to say. The body of the antenna base matching coil must bottom out against the top of mount before the threads of the antenna connector bottom out in the internal connector of the ADAP-II. I wouldn't make any modification to the antenna-mounting end of the ADAP-II without advice from the manufacturer.

nautiwhaler32
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Re: VHF Marine Band Antenna for Small Boats

Postby nautiwhaler32 » Fri May 20, 2016 3:37 pm

Thanks Jim for you previous response to my question.

Yes toniintc if you could please let us know what GAM says. I am about to order this setup but will now wait to see what you hear back. Thanks in advance!
1996 Outrage 17 -Red Bank, NJ

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Re: VHF Marine Band Antenna for Small Boats

Postby toniintc » Fri May 20, 2016 10:55 pm

I looked at the fitting of the GAM SS-2 antenna into the GAM ADAP-2 mount again. The internal diameter of the ADAP-II is 1.000 inches and the outside diameter of the SS-2 is 1.003 inches. I was just not twisting the antenna hard enough when trying to thread it fully into the mount. After going back and forth a few times, the SS-2 is seated down in the ADAP. This is all probably intentional to give a good fit, and I was just trying to be too careful.
Last edited by toniintc on Sat May 21, 2016 4:57 pm, edited 1 time in total.

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Re: VHF Marine Band Antenna for Small Boats

Postby toniintc » Sat May 21, 2016 1:06 pm

Ok, all done. I finished last night about 11:00 p.m., and, not surprisingly, nothing came across the radio. I went to bed wondering if I did something wrong despite knowing that there would be little radio traffic at that time, especially this time of year. This morning I turned the radio on and started cleaning the boat and heard the Elk Rapids harbor master hail a boat. I was in my front yard about 15 miles away, so that's one good indication.


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jimh
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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Sat May 21, 2016 7:47 pm

You installation looks good. Thanks for sharing the nice images of your work.

A useful method to assess the performance of an antenna and radio is to listen for NOAA Weather Broadcast stations that are quite distant. It is typical to be able to receive NOAA stations at ranges of up to 100-miles. I have written about the method in some detail in an article at

Assessing VHF Marine Band Antenna Performance Using Distant NOAA Weather Radio Broadcasts
http://continuouswave.com/whaler/reference/antennaRange.html

Find stations in your region by using this index:
http://www.nws.noaa.gov/nwr/Maps/

toniintc
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Re: VHF Marine Band Antenna for Small Boats

Postby toniintc » Sun May 22, 2016 10:56 pm

I can pickup NOAA stations quite a ways away. I could also receive the Sault Ste. Marie Coast Guard. Boat to boat communication is solid. Overall I couldn't be happier with it. Thanks again!

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Sun May 22, 2016 11:37 pm

Coast Guard radio transmissions on Channel 16 or Channel 22A are usually linked and often can be simultaneously transmitted from multiple locations. Although you might hear the station identify as "Coast Guard Sault Ste. Marie," you are probably hearing the signal from a transmitter much closer to you. It is extremely unlikely you could copy a VHF transmitter in the Soo from your location around Elk Rapids.

With the new RESCUE 21 radio system, there are many radio installation sites that you could be hearing. Take a look at my article about RESCUE 21 sites in the Great Lakes to see where they are located:

Rescue 21 Radio Installations
http://continuouswave.com/whaler/reference/Rescue21Stations.html

You are probably hearing a transmission from the BLISS or CENTRAL LAKE sites.

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Wed Jun 29, 2016 1:08 pm

I just spoke with Shakespeare Customer Service to confirm their Model 498 light-duty four-foot extension mast is no longer available. A possible substitute is their model 4008-4 extension mast. The 4008-4 is a 50-inch extension mast made from a fiberglass tube. There are three drawbacks:

--the 4008-4 is more expensive than the 498; the 4008-4 lists for a ridiculous $162. The street price is somewhere around $60 to $90; in comparison the 498 was $40 to $55 at many vendors;

--the 4008-4 is made with a fiberglass laminated tube which, in my opinion, is not as resistant to fracturing as the polycarbonate tube in the model 498; and,

--the threaded fitting on the 4008-4 onto which the ADAP-II must be threaded is now metal; this means you can no longer easily trim those threads to make a cleaner fit with the threaded coupling on the ADAP-II, if necessary. I suspect you can cut off some of the threads on the 4008-4, but you will need a better saw and take more care cutting the chrome-plated metal ends.

Compare at:
http://shakespeare-ce.com/marine/produc ... sion-mast/

An alternative is to visit a plumbing supply store. You can buy some PVC tubing and cast PVC fittings, and use them to make your own extension mast for about $10. I have not tried this, so I don't know how well the usual PVC solvent-adhesive will work, and if it will be strong enough for this application.

Other alternatives for four-foot extension masts are

--Shakespeare Galaxy 5228-4 Extension Mast; about $100 at Defender.com

The main article on this topic in REFERENCE has been updated to reflect the 498 extension mast may not be easily located now that it is no longer in production.

UPDATE: It appears that Shakespeare has resumed production of a light-duty 1-foot extension mast, their 4364-B is available at DEFENDER.COM for $28. But it's only a 1-footer.

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Re: VHF Marine Band Antenna for Small Boats

Postby Ridge Runner » Wed Jun 29, 2016 10:13 pm

Shakespeare also makes a 24-inch stainless steel extension mast in standard 1 x 14 threads design with male upper and female lower. Part number 4700-2, and the price is reasonable at $45 on Amazon. If 48-inch is needed two extension masts could be screwed together with thread lock applied. I imagine this extension would be very durable and be an interesting almost all stainless steel look from the antenna mount up to and including the GAM SS2 antenna.
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peteinsf
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Re: VHF Marine Band Antenna for Small Boats

Postby peteinsf » Wed Aug 17, 2016 10:03 am

I was looking at the GAM SS-2 and was thinking the Shakespeare 4400 or 5241-R would do the same job but simplify the installation since the antenna has the coax exiting the coil base vs the PL259 on the bottom of the GAM SS-2.

I do see two drawbacks:

1) you can't repair a damaged coax easily.
2) if too short to get to the radio, the supplied 15' cable would need to have an in-line junction (FME, BNC, N-Connectors, etc). I just realized I already own all the FME goodies from another radio project.

Has anyone used the small Shakespeare models on a 4' extension.

Pete

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Wed Aug 17, 2016 11:03 pm

The base of the GAM SS-2 does not have a PL-259 connector. It has the opposite gender and will mate with a UHF-series connector like a PL-259.

I would not presume that every other 3-foot metal whip antenna on the market will work as well as the GAM SS-2. Yugo and Audi both make small cars, but they're not the same performance. This also applies to radio antennas. Some work better than others.

The beauty of the GAM antenna is the modular system. Not having the coaxial transmission line captivated to the base matching coil of the antenna is--in my mind--bonus for the GAM.

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Sun Nov 20, 2016 8:15 pm

I notice that Gam Electronics has added a new antenna, designated the GAM SS-2 MARINE antenna. This antenna appears to be the same as the SS-2, but Gam says this antenna will be carefully pre-tuned for 156.8-MHz for best performance across the marine band. If ordering a Gam SS-2, be certain to specify you want the Gam SS-2 Marine version if you don't want to have to cut the whip to length yourself. Cutting the whip to length is not hard and the antenna will give you a chart for the proper length. If there is a substantial increase in price for the pre-cut version, I recommend buying the standard version and cutting the whip to length according to the provided cutting chart.

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Re: VHF Marine Band Antenna for Small Boats

Postby jimh » Sat Mar 24, 2018 10:17 am

On the general topic of VHF Marine Band antennas for small boats, I have written two new article about two other antennas:

--the MORAD VHF-156HD, and

--the COMROD 8-foot VHF Marine Band antenna

Both of these antennas are substantially more expensive than the GAM SS-2. Follow the hyperlinks above to read more about them.

I also recently posted an article describing the disassembly of a typical "8-foot" fiberglass-encased antenna which revealed the actual radiating portion was only 36-inches long.

I removed some anecdotal comments in this thread about these other antennas and recommend reading the three other articles (linked above) for more information on the antennas where they are described and illustrated in detail.