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| How much more range can I expect to get out of a 5ft antenna vs a 3ft antenna on the water? Gain and MHz being pretty much the same on both antennas?
Will the extra 2 ft result in that much more coverage?
Im comparing a 5ft Fiberglass Cobra to a 3ft Wire Low Profile Shakespeare. | |
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Posts: 431
| I always hear why isn't it longer? | |
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Posts: 1316
Location: Lebanon,Mo | Nope...wont gain a thing with no matter what antenna you use.It's all in the radio and Coax. Say you have a radio with 20watt output with a short antenna,and a radio with 10watt output and a long antenna and the short combo will out perform your other radio 10 to 1. Same as Coax,the shorter coax will perform better than the longer one since you loose alot of gain with the longer coax.Another tip for better performance is if you have extra coax is to wrap the wire in a figure 8 pattern rather than a circle pattern before you tie the extra away. | |
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Posts: 548
Location: MN | I beg to differ. It's all in the antenna. Increasing talk power with more watts will help your transmit, but in no way will help you hear better. You can't work em if you can't hear em. Higher gain antennas will perform much better. ( more capture area ) And the figure eight thing, never heard of it. Wrapping coax in a circle will create a choke. A good thing closer to the antenna. Your right about the length of coax, although in a boat I doubt you would ever have a length long enough to actually attenuate your signal to a point you could tell the difference. FM is line of sight... so length does matter.
Good Luck
Nick
missourimuskyhunter - 9/9/2012 8:14 PM
Nope...wont gain a thing with no matter what antenna you use.It's all in the radio and Coax. Say you have a radio with 20watt output with a short antenna,and a radio with 10watt output and a long antenna and the short combo will out perform your other radio 10 to 1. Same as Coax,the shorter coax will perform better than the longer one since you loose alot of gain with the longer coax.Another tip for better performance is if you have extra coax is to wrap the wire in a figure 8 pattern rather than a circle pattern before you tie the extra away.  | |
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Posts: 1663
Location: Kodiak, AK | You're both right. You can have a 40' long antenna, but without a radio to push it, you won't be able to broadcast from the front of the boat to the back. But at the same time, you can have a handheld powered by a nuclear reactor and with it's 5" antenna won't be able to broadcast any further than a standard mounted radio with a 3' whip.
FM is line of sight, so a longer antenna can make a difference, but it's not a magic wand that'll let you transmit or recieve 300 miles. I kinda chuckle when I see guys with the huge fiberglass antennas (usually laying down) and then have a standard off the shelf radio installed. But being line of sight, a longer antenna is needed when wanting to communicate distances that a handheld can't even begin to reach, so in addition to my handheld, I have a mounted radio and a 3' whip and I can talk to Sector Detroit (downtown Detroit) from the St. Clair River. It depends on alot on the body of water you're on, the number of repeaters ashore and who you're wanting to talk to. If you're on most navigable water, there'll be repeaters to help you. If you're on LOTW, I doubt there many or any repeaters.
I say get the whip antenna. It's served me fine communicating and even getting involved in three off duty SAR cases and the occasional PAN-PAN. I relayed a cancel PAN-PAN from Tow Boat US to Sarnia CG radio just a few weeks ago. Basically I was talking to Lake Huron from the shipping channel in LSC...on a 3' whip and repeaters.
Edited by esoxfly 9/10/2012 8:06 AM
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| Great info here but looking for a simpler answer.
25 w radio
3 ft Shakespeare Whip antenna vs 5 ft cobra glass antenna with pretty close to the same specs outside of the height
Will I get any more noticable range by going with the 5ft antenna? | |
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Posts: 433
Location: Cedarburg, Wisconsin | Slightly more range, but probably not enough to be worth the effort to change. An 8'er would help a lot more as your line of sight would improve more. It's not so much only the lenght of the antenna but how high the tip is above you. I mounted a 5 footer on the top of my garage about 8 miles inshore from Lake Michigan and I could hear boats as far away as 20 miles, sometimes more. The same antenna on the boat would barely pick up any chatter at all. | |
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Posts: 1663
Location: Kodiak, AK | Guest - 9/10/2012 12:06 PM
Great info here but looking for a simpler answer.
My simple answer is above...get the 3' whip. Unless you're fishing offshore in the Gulfstream, there's seldom a need to talk 100 miles away and even with the glass rod, you'll still have to push your transmissions that far. You may hear them, but they won't hear you...which nullifies the need for a larger antenna because a one-way conversation doesn't work very well. Get the 5' or 8' if you want, but I've never needed one in all my time on LSC or the nearshore water of Kodiak and they take up a helluva lot of room. | |
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Posts: 548
Location: MN | If your in an area that utilizes repeaters use the smaller antenna.
Nick
esoxfly - 9/10/2012 12:07 PM
Guest - 9/10/2012 12:06 PM
Great info here but looking for a simpler answer.
My simple answer is above...get the 3' whip. Unless you're fishing offshore in the Gulfstream, there's seldom a need to talk 100 miles away and even with the glass rod, you'll still have to push your transmissions that far. You may hear them, but they won't hear you...which nullifies the need for a larger antenna because a one-way conversation doesn't work very well. Get the 5' or 8' if you want, but I've never needed one in all my time on LSC or the nearshore water of Kodiak and they take up a helluva lot of room. | |
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Posts: 121
Location: Plymouth IA | Being the RF engineer as one of my jobs, the length of a full wave Marine Band VHF antenna is 75.35 inch long "mid band ideal". In the real world we live in, half wave 37.9 inch for mid VHF marine band is good enough. Mounting the proper length antenna higher equates to line of sight distance, not longer antenna at wrong length. RF ground plain is almost as important as height. That's why on the water you get great coverage with a half wave antenna. So if the one antenna is really 5 ft and the other is 3 feet go with the 3 foot. Yes the extra length multiplier for the 5 foot can be made up electronically, but I would go with the 3 foot. | |
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Posts: 2754
Location: Mauston, Wisconsin | Listen to misterperch. Otherwise, take the boat to a shop that specializes in two way radio communications. Ask around, these same folks usually take care of police, ambulance, taxi, and business FM communications radios.
Tell them you want them to check the VSWR of the system. Be sure that you have them check the primary frequency's you are likely to be using, i.e., emergency marine channel & talking to buddie's channels. The closer the channels are to together with each other for frequency the better.
http://www.google.com/webhp?source=search_app#hl=en&sugexp=les%3Bcp...
Most off the shelf radio systems -> radio, coax, and antenna are not optimized for specific frequencies. Ask them to tune the transmitter output for lowest VSWR at the mid-point between the frequencies you are using. If the radio in question has a final output amplifier that can be tuned, they can also lock it in for maximum line-of-sight transmission- lowest VSWR at your primary frequency. They have to do it as a system = radio->coax-> antenna.
http://www.navcen.uscg.gov/?pageName=mtvhf
Don't forget the curvature of the earth, if you can't see it , you usually can't talk to it unless you have a brute horsepower FM transmitter or its very close by.. behind an island, etc. Then there's also "skip" but that something that is totally atmospheric controlled. I have talked between Ft. Bliss, Texas (Dona Anna Range Control) and Ft. McCoy, WI on a 75W radio FM radio that I tweaked for our our firing range and air traffic control operational frequency. I was surprised when McCoy Tower came back on the radio check call. But, I would never bet on skip.
It's already been said, if you can hear them and they can't hear you or the reverse, its a waste of time. Their VSWR may be bad, as has been stated previously the length of the coax and how its installed are a major factor. If the VSWR is low on your radio the majority of the power output is leaving the antenna. Beyond that, what you hear is driven by receiver sensitivity and where you have set the squelch. If its an emergency situation - turn off the squelch, that will allow you to hear the weaker signals. Longer antennas are better, but also a major pain on a boat. If you're only trolling no problem, put it on a mast. Casting W/multiple people, etc. no fun if you're the guy who keeps wacking the antenna with his rod...... Commercial fisherman and charter captains understand the on the water value of a good radio. Maybe one area where cheap is not the way to go......
Good luck,
Al
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| I'd go with a Shakespere Galaxy XT in 4'. Had one on my last Tuffy, and it worked better than the Stainless whip antennas.
My 8' Galaxy I had on my 2002 Lund worked the best. I was used as a relay station between Jason Smith(Whip) and the Extreme One(Also Whip) during the Cass fall outing that year. Didn't matter where I was, I could hear and talk to either one, but they couldn't always hear or talk to each other.
Edited by Shep 9/12/2012 2:28 PM
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Antenna ?