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ContinuousWave: Small Boat Electrical
VHF antennas: 8-foot whips
|Author||Topic: VHF antennas: 8-foot whips|
posted 10-22-2007 04:36 PM ET (US)
I can't seem to find any recent awards or comparison tests of 8-foot VHF antennas. NMEA hasn't published this year's award recipients yet and they did not have an antenna award recipient for 2006.
Which 8 foot VHF antennas are deemed the best of their class?
FYI, I heard the ICOM M604 won this year's NMEA award as the best VHF radio.
posted 10-22-2007 05:20 PM ET (US)
I just replaced my 8 month old Shakespeare (left it up under that #@% bridge again!)
I replace it with Shakespeare’s 5225-XT.
After hooking it up to the back of my Icom 422 and keying the microphone, I asked for a radio check and received a response from Battery Park, New York, NY. That's a distance of twenty miles in a straight line, and that was all the testing I needed.
posted 10-22-2007 06:01 PM ET (US)
Shake makes several grades of antennas. The 5225-XT is in
their Galaxy line, which is their good line, and is what I
have (and what I have another of in the rafters (I broke it,
did a really ugly glass job to repair it, worked fine, I
replaced it because my glass work was so ugly. The 5225-XT
will run around (probably a bit over now) $100.
One thing to watch is the length of the cable. Their cheap
Antennas aren't a rapidly changing market. Practical Sailor
posted 10-22-2007 07:54 PM ET (US)
Thanks for the input guys.
I currently have a Galaxy 5225 XT Shakespeare mounted on my 170 Montauk. I too have sent and received responses from 20 miles away with my ICOM 402, too bad it's broken.
I have an appointment with and marine electronics shop on October 31 to purchase and install an new VHF radio. The electronics guy said that they will check my current antenna and if it is not up to par they will recommend replacing it with a Digital Antenna model 529. He said since I'm getting a top-notch radio, I should also have a top-notch antenna.
I had read somewhere that the Digital Antenna 529 won the 2002, 2003 and 2004 NMEA award as the product of the year.
I enjoy fishing/boating alone in the ocean. My favorite fishing spots are up to 40 miles away from port so I don't mind spending a few more bucks to get a radio/antenna that is top notched.
posted 10-22-2007 08:15 PM ET (US)
The best 8-foot antenna is a GAM Electronics whip on a 4-foot extension.
posted 10-22-2007 09:44 PM ET (US)
Don't replace that antenna or let them replace it. if it works you will be spending money you don't need to spend. Replace the VHF and leave the antenna or it will endup on one of the mechanic's boats. I have the same antenna and even lying against the top of the gunnal I can transmit and receive 15 to 20 miles away, if I actually remembered to lean over and flip it up, no telling how far I could reach.
posted 10-22-2007 09:56 PM ET (US)
I can second the opinions of the Shakespeare 5225XT - I have one on the top of my radar arch and have been very pleased with the range, however, I'm intrigued by the GAM electronics idea.
The GAM Electronics antenna bears some discussion, as Jim's (and HOME ASIDE's matching set) is one of the best radio's I've heard on the water. I don't know if it is from the radio itself, or the antenna, or a combination of both...the signal from their boats is *C R Y S T A L* clear. The only complaint I have is that the VOLUME of their transmittal is low.
However, I don't have any information about how those setups RECEIVE signals.
I do know that I can often hear boats 20-25 miles away on Lake Michigan on the 5225XT.
posted 10-22-2007 10:13 PM ET (US)
Do I want a 12 foot antenna on a 170 Montauk?
posted 10-22-2007 10:49 PM ET (US)
"The best 8-foot antenna is a GAM Electronics whip on a 4-foot extension."
I see, a 4-foot extension with a 4-foot GAM whip antenna.
|Tom W Clark||
posted 10-22-2007 10:57 PM ET (US)
It was with great pleasure that I was finally able to take my 8 foot Shakespeare VHF antenna to the dump. Good riddance.
I love my 4 foot GAM. It is so diminutive you can hardly tell it is there.
posted 10-23-2007 12:23 AM ET (US)
I should add this qualifier to my statement, "on a small boat."
I explain the concept in my article in the Reference section. I have been very pleased with the results from the 4+4 antenna installation. I am also pleased to hear from others who are using it and got good results as well.
|Tom W Clark||
posted 10-23-2007 12:35 AM ET (US)
Honestly Warren, on your boat I would mount a GAM on a stainless steel rail-mount ratchet just below the bend from the side to the top of the console grab rail. Then drill a hole in the rail, elongate (oval) the hole and run the coax down the tubing of the rail to the console.
This will give you a very clean installation and gain you some elevation over where your mount is now, and you will still be able to fold the antenna down to put a mooring or console cover on without interference.
If you want to be really fussy, have a welder run a small bead around the edge of the hole you drill in the rail to create an even smoother edge. That is how my RADAR arch was detailed for the coax cables.
posted 10-24-2007 12:30 AM ET (US)
You do NOT want a 12' antenna on a small boat. The 12' is
rated 9dB because it projects a VERY flat signal pattern.
A small boat will rock enough to send all the energy to the
stars or fishes. When you get a 135' boat, get the 12'
I would not drill a hole in the rail. I'd just tiewrap the
The Digital 529 did not do as well as the Shake in the
If your towing config will allow it, do a Shake on a 4'
posted 10-25-2007 08:16 PM ET (US)
Warren, not trying to “pit” one antenna against another but you should be aware of something. Your current 5225-XT is considerably lighter than the Digital model. Part of this is the filling material digital used to seal the element inside the outer casing antenna case (the 5225-XT does not have this). Be aware the 529 will place more stress on your mount than your current antenna. Like me, you have the 170 Montauk and when you go crashing through those offshore waves in that small boat, your mount will be under more stress.
A word to the wise...
posted 10-25-2007 08:26 PM ET (US)
I hear you about the antenna being stressed in rough waters.
I actually velcro my antenna at the top of my console rail for additional support. (Not shown on the photo below.)
posted 10-26-2007 06:06 PM ET (US)
Another thought on the extension is Shakespeare makes stainless extensions in 1 and 2 foot lengths. I have 4 foot XT antennas on one foot extensions. One is for the VHF and is located on the port side away from radio and the other is a FM radio antenna. I should have gotten the two foot extensions , and might some time , but they work great. You could go with a stainless two foot extension and have a stainless clamp to attach to railing on console then go with a four foot antenna. Just an option to the four foot extensions.........Jack
posted 10-26-2007 06:07 PM ET (US)
Oops, there are some pictures of the antennas in my profile.........Jack
posted 10-27-2007 09:33 AM ET (US)
Warren, Consider upgrading you radio to an Icom 604 if you want superior radio performance. A 602 (older model) coupled with a 8 foot Shakespeare Galaxie antenna is the rig I have and I believe the performance of my rig exceeds or matches any craft in my area including big boats with 12 foot antennas. I boat where there is no Coast Guard or Vessal Assist and your vhf is truly your life line.
The Icom 604 has a more sensitive receiver (rejection 80 db) than your 402 (rejection 75 db).
There is no way a top quality 4 foot antenna will match the performance of a top quality 8 foot antenna on a powerboat application because the gain with the shorter antenna is half that of the larger. The difference in performance may be minor but there is a difference. Why give up performance when there is no corresponding benefit?
Little antennas are for sailboats that heel over and space restricted installations.
posted 10-27-2007 10:13 AM ET (US)
The sensitivity of a receiver is not measured by its "rejection." The figure cited for rejection is some (unspecified) measurement of the ability of the receiver to ignore off-channel signals while receiving an on-channel signal. I do agree that it is an index of better performance, but it is not indicative of the radio's sensitivity.
As I demonstrate in my REFERENCE article, an 8-foot antennas mounted low will not perform better than a 4-foot antenna mounted higher and more in the clear. The range of a VHF ground wave radio circuit is most affected by the height of the antenna.
posted 10-27-2007 11:36 AM ET (US)
If the receiver has a higher ability to ignore spurious signals, the less squelch is needed for a clear signal, hence greater "sensitivity".
Those of us scientifically ignorant must rely on pedestrian sources for our information such as the West Marine catalog. The catalog on page 30, says a tall antenna has more range than a short one. How could there be any dispute about this?
I have used my radio at long range in 8 to 10 foot seas. I have not observed the signal to fade in out as would if the concentrated signal were disapated by the motion of the boat. A wider beam is an admitted advantage of a short antenna.
posted 10-27-2007 11:41 AM ET (US)
The SQUELCH has nothing to do with the ability of the receiver to reject adjacent off-channel signals. In an FM Receiver the Squelch sets a threshold for muting the audio output of the receiver so as to suppress the noise that would otherwise be heard. Raising the Squelch threshold reduces the effective sensitivity of the receiver by simply muting the audio output, but is has absolutely no effect on the actual sensitivity or ability of the receiver to reject spurious signals. The squelch operates in the audio domain, not in the radio-frequency domain.
posted 10-27-2007 11:45 AM ET (US)
If you accept West Marine as the ultimate authority on radio communications, then there can be no dispute about their statements. You'll have to surrender that position before we can discuss the topic further.
posted 10-27-2007 12:13 PM ET (US)
To get back on the initial topic of antennas, I will offer another recommendation for a good VHF Marine Band antenna for use on a small boat:
This antenna is a five-foot antenna in a fiberglass housing. Electrically it is a half-wave antenna, the same length as the GAM SS-2. However, this antenna utilizes a different feed technique--center-fed. There is one problem with a center fed vertical dipole: decoupling the feedline. The Shakespeare 396-1 accomplishes this with a half-wave coaxial sleeve.
The one thing I love about this antenna is your transmitter power goes directly to the radiating element. There are no shunt matching stubs or other devices. Your 25-watts go down the feedline, right to the radiating element, and right into the ether. This is known as a series-fed antenna. Many vertical end-fed antennas have to employ a shunt element in the matching network to permit proper impedance matching. This simple Shakespeare 396-1 has none of this, and therefore there can be no losses in the matching network.
The only disadvantage to the vertical dipole with sleeve decoupling is the potential for antenna currents to flow onto the feedline and distort the pattern. We never see any precise vertical radiation pattern measurements of Marine antennas, anyways, so to speculate that this one suffers more than any other style is not justified. If the decoupling sleeve is well designed, it should suppress this tendency.
The Shakespeare 396-1 is a ruggedly constructed antenna and it is claimed to be used extensively in Coast Guard vessels. The Shakespeare brochure says, " [the 396-1] is probably the most widely used antenna on Coast Guard vessels."
In my own installation I did not opt for this antenna because I wanted to elevate the antenna on a four-foot extension, and I thought that the weight and wind loading of this antenna would be too great for my existing ratchet mount and the light-duty extension I planned. Also the feedline exit at the base is not good for mounting on an extension.
I have not seen any test results from this antenna, and my interest in it is based primarily on my attraction to its very simple electrical design. I think it will give a good account of itself if mounted to advantage, that is, in the clear and not surrounded by metal rails and people. The implied endorsement from the Coast Guard is also a positive influence.
The price of the Shakespeare 396-1 is about $60 at discount retailers.
posted 10-27-2007 12:23 PM ET (US)
Let me also offer an idea for mounting an antenna on a small center console boat:
An advantageous arrangement for an antenna mount on a center console might be to use a 4-foot or 5-foot fiberglass antenna, mounted to a 4-foot extension. Because of the heavy loading that an all-fiberglass antenna creates, the base mount will have to be supplemented with support bracket.
Locate the support bracket as high as possible on the center console. Locate the antenna mount at least one foot lower. This will give proper support and allow a heavy duty 4-foot extension to be use. A 4-foot or 5-foot antenna can be mounted on the extension. The extension is not part of the antenna, and, if of heavy duty rating and well supported by the mount and bracket, the extension could also function as a grab rail.
There is always a tendency for crew to grab onto the base of antennas for supports, so having the two-part mounting arrangement will help the antenna withstand these human loads, too.
posted 10-27-2007 05:05 PM ET (US)
In a marina filled with high dollar powerboats where the owners can afford the best setups money can buy, how many 4 foot antennas do you see? The bigger the boat, the taller the antenna.
posted 10-27-2007 11:59 PM ET (US)
"The bigger the boat, the taller the antenna."
Does that imply: the smaller the boat, the shorter the antenna.
posted 10-28-2007 08:54 AM ET (US)
What is a little boat? I consider my craft small, the bridge clearance on my boat is 9 feet. That is enough distance above the water so concentrated signal of an 8 foot antenna mounted on the t-top at 9 feet is not disapated by surface clutter. I know because the performance of my radio and antenna has been good in all sea conditions.
If the antenna must be mounted on the bow rail or console say two feet above the water a shorter antenna may give better performance. A performance trial would be the only way to determine this.
posted 10-28-2007 01:58 PM ET (US)
the higher the antenna is mounted the better it will work
the lower the frequency the longer the antenna will be
the higher the gain of the antenna the narrower the beam
the more directional the antenna is the higher the gain
The installation and placement should determine which antenna is selected. For instance if you are using a bimini top will the antenna be out of the way? On my 150
If I were to mount an antenna to a center console I would have to consider a ratchet mount with an upper yoke support, this takes a great deal of stress off the single point mounting. I would also prefer that the actual antenna is elevated as far as practical, so I would use either a 4' or 8' extension. I chose to use a base loaded steel whip similar to the GAM antenna made by Shakespere with the included 1" 14 thread mounting and about 36" whip. You could use a 4' or 8' fiberglass antenna on top of the extensions as well but the overall length might be too cumbersome.
On a T top I would consider whether I needed to fold the antenna down or not, if clearance was not an issue then an 8' antenna would be perfect. If clearance is an issue then the 3 ft base loaded coil with a spring may solve that problem.
Truth is if properly installed all of these antennas will work well. I would not be overly brand concious but instead would be application concious.
posted 10-28-2007 02:36 PM ET (US)
I think I understand.
A 4 foot antenna which is unobstructed may work as well if not better than an 8 foot antenna that is obstructed by a center console, people, motor, etc.
The higher the base of an antenna is mounted the better. There would be less chance of obstructions the higher you go and the line of sight for the antenna will be further.
If I add a 2 foot base extension to my existing antenna it will extend off the bow by 2 feet in the down position. I think 4 feet is too much length to stick out off the bow in the down position.
Or I can just leave everything alone.
I hate making decisions.
posted 10-28-2007 04:10 PM ET (US)
One thing that I have brought up before and I am not a broadcast engineer but have worked in broadcast is that people should not stand next to or near any antenna radiating RF. By putting the antenna over your head as some of us have this is minimized as much as possible. Somewhere on this site there is a photo I sent in.
posted 10-28-2007 04:16 PM ET (US)
Found it a photo of my setup and it works well for me.
posted 10-31-2007 11:05 AM ET (US)
Warren, I sent you an email with a photo of the GAM antenna setup on my outrage 18 (4'GAM antenna + 4' extension). I have been very happy with it. While cruising in the Napa River and or the SF bay, I receive transmissions from Montery and other locations from Bodega Bay to out to the islands., which is quite a distance. I'm not sure what the actual transmission distances are for sending but I'm sure it is more than adequate. I hope this helps,
posted 10-31-2007 03:05 PM ET (US)
Has anyone looked at the 4' extensions and determined which one is best? I saw them offered by Digital and Shakespeare. Any others out there worth mentioning?
posted 11-01-2007 07:13 AM ET (US)
When I bought mine I got the lighter weight one from Shakespear. They had a heavy duty version which now I wish I had. I wrap a piece of velcro around extension and the rail. People tend to grab the extension thinking it is the rail. You can undo the velcro and let the antenna down when trailering.
posted 11-01-2007 10:32 PM ET (US)
...i was thinking the heavy duty mast would be the way to go... thanks.
posted 11-02-2007 07:30 AM ET (US)
I bought the Digital 4' entension to use with my Digital 528 4' antenna. The extension is well-made but extremely heavy relative to its size. It placed so much additional stress on my rail mount, I had to take it off and simply use the 4' antenna screwed directly onto the rail mount.
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