Marine VHF antenna?

[GatorMike]

I have just recently purchased a new boat which I am trying to set up the way I want it. My old 20 foot proline had one of those 12' antennas that lays on the gunwale when not in use and gets stepped on when someone boards the boat. My new boat a 19' cc Welcraft is a little sleeker design and I don't think the long antenna will look that good and besides I hate the way those things are always in the way. I am looking for a short antenna that can be used with a marine vhf radio. I would like to find something about 3' long that could be mounted on the center console. I never go much more than 20 miles out so I don't need something that will reach out a long way. Anybody know of a good, short, mid range, cheap antenna that will suit my purpose? Oh if I must I can scratch the cheap out of my description.

 

[Jack Shellac]

Re: Marine VHF antenna?

Shakespeare makes a 3' whip SS antenna that seems to work well on my boat. Mine's mounted on the CC grabrail so it will fit under the bimini top. Like you, I'm seldom out far enough to give any idea on max range.

 

[cjones4@hvc.rr.com]

Re: Marine VHF antenna?

If I were going 20 miles out I think I would want all the height I could get. Take a look at the chart on this page that shows the effect of antenna height:<br /><br /> http://www.catfleet21.org/rigging/June.htm

 

[POINTER94]

Re: Marine VHF antenna?

I'm with mooner. We used to install those steel units on the top of mastheads which benefited from the additional height provided by the sailboats main mast.<br /><br />VHF is line of sight (primarily). Something taller would be preferrable in almost any situation.

 

[rwidman]

Re: Marine VHF antenna?

According to the instructions you get with an antenna, it must be some distance from any humans while transmitting. This is for health reasons. While you may choose to ignore this warning or have to ignore it to get the antenna mounted on the boat, the center console will be very close to the operator. Full sized VHF antennas are about eight feet long and you can buy a mount that allows them to be laid down when not in use.<br /><br />I would strongly consider a quality full sized antenna and a stainless steel lay down mount. Your VHF is a piece of safety equipment and shouldn't be compromised.<br /><br />You can get some information here:<br /> http://www.shakespeare-marine.com/antennas/whichant.htm

 

[GatorMike]

Re: Marine VHF antenna?

If height is the determining factor wouldn't I get about the same elevation from a 3' whip mounted on the top rail of a 6' windshield as I would get from an 8' antenna mounted 2' above the water on the side of my boat?

 

[Dunaruna]

Re: Marine VHF antenna?

Heres a couple of links, the first one is a detailed explaination of radio range from ThomWv.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=27;t=000553#000001 <br /><br /><br />antenna range table <br /><br /><br />Aldo

 

[Buttanic]

Re: Marine VHF antenna?

You may be 20 miles offshore but how far are you from the nearest Coast Guard radio tower. I would want all the height and range I could get.<br />I know there may be other boats nearer than the CG tower but they may not be monitoring chanel 16. The CG is the only one you can depend on to hear you.

 

[waterone1@aol.com]

Re: Marine VHF antenna?

My 2 cents worth. First of all You should not have to worry about safe exposure limits in the VHF band, unless you were transmitting ilegally<br />with more than 100 watts pep (standard marine radio's are 25 watt). Even at the 100 watt level, you would still be safe with normal boat communications ( the transmitter would not be transmitting for 1 hour straight).<br />The other posts about line of site, and height of antenna are dead on.<br />Your VHF is an important SAFETY item for your boat, don't make it useless for "cosmetic reasons". You wouldn't cut your life preserver in half to make it more comfortable....would you ?

 

[rwidman]

Re: Marine VHF antenna?

Originally posted by GatorMike:<br /> If height is the determining factor wouldn't I get about the same elevation from a 3' whip mounted on the top rail of a 6' windshield as I would get from an 8' antenna mounted 2' above the water on the side of my boat?

You might have the same elevation but an eight foot antenna can transmit a stronger signal than a three foot antenna. It has to do with wavelength and frequency. Check the link I posted above.

 

[rwidman]

Re: Marine VHF antenna?

Originally posted by waterone1:<br /> My 2 cents worth. First of all You should not have to worry about safe exposure limits in the VHF band, unless you were transmitting ilegally with more than 100 watts pep (standard marine radio's are 25 watt). Even at the 100 watt level, you would still be safe with normal boat communications ( the transmitter would not be transmitting for 1 hour straight).<br />

Just quoting the instructions that came with the antenna. As I said, you can choose to ignore them.

 

[18rabbit]

Re: Marine VHF antenna?

Gator Mike – get yourself a Morad 156-HD antenna. The best there is, can be found atop USCG cutters, and their rescue boats designed to roll Antenna is just 4-1/2 ft tall. A base to mount to a standard 1 in thread adds another 3 inches. Antenna and optional base costs about $130. See it at the top of page 4 here:<br /><br /> http://www.rell.com/pdfs/Moradcatalog.pdf <br /><br />If you need it higher, you can buy a stanchion (2, 5, 8, 10, or 12 ft) to extend the height.<br /><br />Give some thought to what Rwidman references. I believe current FCC requirements are the antenna (not greater than 9db gain) must be mounted 5 meters above the boat deck to limit exposure while transmitting. I have never heard of the FCC-police going after boaters or antenna installers. But there is a reason why that rule exists and there is no harm in playing it safe.<br /><br />Edit: Quick thought: there are a lot of people here from all over the place. Not everything posted is applicable to all areas. Here in the SF bay area the USCG has their primary antenna on top of a little lump of ground called Mt. Diablo*. It is up there over 3000ft so the theoretical range is over 70 miles out to sea even if your antenna is mounted at sea level. My understanding is most USCG antenna are mounted over 300ft high and have a range at least 25-miles out…more if your boat’s antenna is above sea level. You should check with USCG in your local area to see what the actual range is for VHF in your area…it may exceed your boat’s range even with a cabin top mounted antenna.<br /><br />*For those will a lack of California geography, you can stand on top of Mt Diablo in the east bay area, and on a clear day, you can see Half Dome in Yosemite Nat’l Park across the state (about 120 miles the way the crow flies).

 

[gutshot grouper]

Re: Marine VHF antenna?

Look at manufacturers spec sheets, a 3db gain antenna, which is about all the gain you will get when going from 3foot to 8foot is equivalent to doubling the output power from the transmitter, is a worthwhile investment and can poss. make the diff. between being heard or not heard if you have an emergency, Old Radio Guy

 

[waterone1@aol.com]

Re: Marine VHF antenna?

Did someone say that the antenna should be mounted 5 meters above deck to limit exposure..... without getting too critical, that would be close to 15 feet above deck....better start calling ahead for bridges to "open" so your antenna can pass under them.....LOL.

 

[waterone1@aol.com]

Re: Marine VHF antenna?

As gutshop said....a full length antenna will give you more gain from your transmitter. That equals power. After all, a 25 watt transmitter that is connected to a dummy load will not be heard, no matter how "high" the dummy load is. The same transmitter, connected to a 1/2 wave antenna will be heard for several miles.

 

[waterone1@aol.com]

Re: Marine VHF antenna?

Sorry, some of the eroneous info on here got me going. First of all, any antenna that produced 9 db of gain or above would actually be a multiple element, or collinier array, that simply is not practical nor have I ever seen one on a pleasure boat. What you are really looking for is a 3 - 6 db gain antenna that would be between 4-8 ft. while it may be attractive to install a 3 ft antenna on your windshield, you will have very short tramsmitting capabilities. As gutshot stated, a full length antenna of 1/2 wave or 5/8 wave is preferred. Again, some of the small antenna's posted earlier might work on a sail boat mast that is 20 -50 feet above the water line, they are not recommended to be used on a power boat, a few feet (or even 6ft) above water line. Get a real antenna and be safe.

 

[18rabbit]

Re: Marine VHF antenna?

From page iii of the ICOM IC-602 VHF radio manual. OET Bulletin 65 “Evaluating Compliance With FCC Guidelines For Human Exposure to Radiofrequency Electromagnetic Field” can be found on www.fcc.gov. Good luck in trying to get either ICOM or the FCC to argue the issue with you. <br /><br />

<br />Icom requires the radio operator to meet the<br />FCC Requirements for Radio Frequency Exposure.<br />An omnidirectional antenna with gain not<br />greater than 9 dBi must be mounted a minimum<br />of 5 meters (measured from the lowest point of<br />the antenna) vertically above the main deck and all possible<br />personnel. This is the minimum safe separation distance estimated<br />to meet all RF exposure compliance requirements. This<br />5 meter distance is based on the FCC Safe Maximum Permissible<br />Exposure (MPE) distance of 3 meters added to the<br />height of an adult (2 meters) and is appropriate for all vessels.<br /><br />For watercraft without suitable structures, the antenna must<br />be mounted so as to maintain a minimum of 1 meter vertically<br />between the antenna, (measured from the lowest point of the<br />antenna), to the heads of all persons AND all persons must<br />stay outside of the 3 meter MPE radius.<br /><br />Do not transmit with radio and antenna when persons are<br />within the MPE radius of the antenna, unless such persons<br />(such as driver or radio operator) are shielded from antenna<br />field by a grounded metallic barrier. The MPE Radius is the<br />minimum distance from the antenna axis that person should<br />maintain in order to avoid RF exposure higher than the allowable<br />MPE level set by FCC.<br /><br />FAILURE TO OBSERVE THESE LIMITS MAY ALLOW<br />THOSE WITHIN THE MPE RADIUS TO EXPERIENCE RF<br />RADIATION ABSORPTION WHICH EXCEEDS THE FCC<br />MAXIMUM PERMISSIBLE EXPOSURE (MPE) LIMIT.<br />IT IS THE RESPONSIBILITY OF THE RADIO OPERATOR<br />TO ENSURE THAT THE MAXIMUM PERMISSIBLE EXPOSURE<br />LIMITS ARE OBSERVED AT ALL TIMES DURING<br />RADIO TRANSMISSION. THE RADIO OPERATOR IS TO<br />ENSURE THAT NO BYSTANDERS COME WITHIN THE<br />RADIUS OF THE MAXIMUM PERMISSIBLE EXPOSURE<br />LIMITS.<br /><br />Determining MPE Radius<br />THE MAXIMUM PERMISSIBLE EXPOSURE (MPE) RADIUS<br />HAS BEEN ESTIMATED TO BE A RADIUS OF<br />ABOUT 3M PER OET BULLETIN 65 OF THE FCC.<br />THIS ESTIMATE IS MADE ASSUMING THE MAXIMUM<br />POWER OF THE RADIO AND ANTENNAS WITH A MAXIMUM<br />GAIN OF 9dBi ARE USED FOR A SHIP MOUNTED<br />SYSTEM.

 

[JasonJ]

Re: Marine VHF antenna?

Dang, I have my 8 footer mounted on my center console. Guess it is within 1 meter of my noggin. Oh well. In the Army, the antennas were quite close to personnel when mounted on the turret, they pushed a LOT more power than a marine VHF, and there was never an issue. You are exposed to more standing in front of your microwave oven, so I wouldn't quite worry about it. Just don't hug the thing and talk for three hours straight with it.....

 

[waterone1@aol.com]

Re: Marine VHF antenna?

Rabbit, DO you own a boat ? Do you have a clue ?<br />I don't need to "argue" the issue with ICOM. I have more authority than they do. I am a licensed radio controll operator, they are not. By the way,the minimum distance (3 meters) is more than accomplished by the distance between antenna and operator on most cabin cruisers. Further more, the windshield frames on most boats are also grounded, as in, providing a barrier for the operator from radio waves.

 

[BillP]

Re: Marine VHF antenna?

GatorMike,<br />I use an 8' Shakespeare that was approx $125. I've also used several of their 8' economy brand antennas (lift and lay) and all had good performance. I had a short Shakespear on top of a sailboat mast and listened to the USCG station approx 50 miles away (Bimini to Miami). Their economy versions are good values for small boats. <br /><br />18rabbit,<br />Thanks for posting the info on mounting distance. For all these years I've mounted the antenna on outboards so I could reach it from the helm. I'm going to change mounting locations now and be safe...instead of sorry. <br /><br />bp