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#1
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I am going to add a fix-mounted VHF radio in my boat. I would like to
know whether I should get a 3dB 3-ft antenna or a 6dB 8-ft antenna to mount on the T-top. My questions a - Books and people in this newsgroup recommend 6dB 8-ft antenna for a small powered boat. This sounds good. But I am wondering whether a 8-ft antenna is too large for my 18-ft boat. Will this make the boat "look" very top-heavy? Do people really use a 8-ft antenna in a small boat like mine? - The other alternative is a 3dB 3-ft antenna and accepting the reduced range. Does a 3dB antenna provide a good enough range given the fact that I won't go too far away from the shore (because the boat is considered as a "bay boat")? - According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? Thanks for any info in advance. Jay Chan |
#2
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![]() wrote in message ups.com... I am going to add a fix-mounted VHF radio in my boat. I would like to know whether I should get a 3dB 3-ft antenna or a 6dB 8-ft antenna to mount on the T-top. My questions a - Books and people in this newsgroup recommend 6dB 8-ft antenna for a small powered boat. This sounds good. But I am wondering whether a 8-ft antenna is too large for my 18-ft boat. Nope. Will this make the boat "look" very top-heavy? Nope. Do people really use a 8-ft antenna in a small boat like mine? Yep. - The other alternative is a 3dB 3-ft antenna and accepting the reduced range. Does a 3dB antenna provide a good enough range given the fact that I won't go too far away from the shore (because the boat is considered as a "bay boat")? Purchase the 8 footer to get the greatest range. - According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? Thanks for any info in advance. Jay Chan |
#3
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JimH wrote:
wrote in message ups.com... I am going to add a fix-mounted VHF radio in my boat. I would like to know whether I should get a 3dB 3-ft antenna or a 6dB 8-ft antenna to mount on the T-top. My questions a - Books and people in this newsgroup recommend 6dB 8-ft antenna for a small powered boat. This sounds good. But I am wondering whether a 8-ft antenna is too large for my 18-ft boat. Nope. Will this make the boat "look" very top-heavy? Nope. Do people really use a 8-ft antenna in a small boat like mine? Yep. - The other alternative is a 3dB 3-ft antenna and accepting the reduced range. Does a 3dB antenna provide a good enough range given the fact that I won't go too far away from the shore (because the boat is considered as a "bay boat")? Purchase the 8 footer to get the greatest range. - According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? Thanks for any info in advance. Jay Chan Thanks for the useful info. I will go ahead to order a 6dB 8-ft antenna and a fix-mounted VHF radio. Jay Chan |
#4
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#5
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Around 1/13/2006 8:33 PM, wrote:
I have a feeling that if mine is a 21-ft boat with a taller T-top (like the Mako center console that I see in ad), I would have chosen a 8-ft antenna. But mine is a small 18-ft boat, and I have a feeling that it just doesn't make the cut for a 8-ft antenna. shrugs I've got an 8' antenna and a 14' boat. I figure that I need every inch of range I can get... http://home.comcast.net/~galmgren/gl...t_7-04_004.jpg -- ~/Garth (.Sig broken) |
#6
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![]() "Garth Almgren" wrote in message ... Around 1/13/2006 8:33 PM, wrote: I have a feeling that if mine is a 21-ft boat with a taller T-top (like the Mako center console that I see in ad), I would have chosen a 8-ft antenna. But mine is a small 18-ft boat, and I have a feeling that it just doesn't make the cut for a 8-ft antenna. shrugs I've got an 8' antenna and a 14' boat. I figure that I need every inch of range I can get... http://home.comcast.net/~galmgren/gl...t_7-04_004.jpg -- ~/Garth (.Sig broken) That is what I have been saying all along. I see no reason not to go with the antenna that will increase your transmission range. |
#7
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On 13 Jan 2006 09:56:30 -0800, "
wrote: According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? There is no need for a ground with a VHF antenna. Either the 3 db or 6 db antenna will be adequate for near shore coastal operation. |
#8
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posted to rec.boats
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![]() "Wayne.B" wrote in message ... On 13 Jan 2006 09:56:30 -0800, " wrote: According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? There is no need for a ground with a VHF antenna. Either the 3 db or 6 db antenna will be adequate for near shore coastal operation. I'm with Wayne on this one. The dB rating plays a relatively minor role in the distance the signal travels. The height of the transmitting antenna plays a larger role. But the height of the receiving antenna is the most important element. Example: A 3' antenna mounted on the top of the gunwale of a small boat might be 5' above the water line. It can travel only 5 miles to another antenna that is only 5' off the water...but can travel 15 miles to an antenna that is 100' high (like at a Coast Guard station). An 8' antenna mounted on the same gunnel can travel 9 miles to another antenna that is only 5' off the water (big difference!), but only travels 18 miles to that 100' antenna (a not so big difference from the 3' antenna). If the CG antenna is 250' above sea level (mounted on a tower on a mountain for example), the 3' antenna can travel 23 miles...and the 8' travels 25 miles. So the question is... Who do you want to call with that radio? Another boat within 5 miles? Then either antenna is fine. The Coast Guard when you're 10-15 miles from shore? Then either antenna is fine once again. Here's a good link to explain this further: http://www.yachtworks.net/Store/antennas.htm |
#9
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posted to rec.boats
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NOYB wrote:
"Wayne.B" wrote in message ... On 13 Jan 2006 09:56:30 -0800, " wrote: According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? There is no need for a ground with a VHF antenna. Either the 3 db or 6 db antenna will be adequate for near shore coastal operation. I'm with Wayne on this one. The dB rating plays a relatively minor role in the distance the signal travels. The height of the transmitting antenna plays a larger role. But the height of the receiving antenna is the most important element. Example: A 3' antenna mounted on the top of the gunwale of a small boat might be 5' above the water line. It can travel only 5 miles to another antenna that is only 5' off the water...but can travel 15 miles to an antenna that is 100' high (like at a Coast Guard station). An 8' antenna mounted on the same gunnel can travel 9 miles to another antenna that is only 5' off the water (big difference!), but only travels 18 miles to that 100' antenna (a not so big difference from the 3' antenna). If the CG antenna is 250' above sea level (mounted on a tower on a mountain for example), the 3' antenna can travel 23 miles...and the 8' travels 25 miles. So the question is... Who do you want to call with that radio? Another boat within 5 miles? Then either antenna is fine. The Coast Guard when you're 10-15 miles from shore? Then either antenna is fine once again. Here's a good link to explain this further: http://www.yachtworks.net/Store/antennas.htm Thanks for the explanation of the reason why a 3-ft 3dB antenna may be all I need. I go home and check the possible location for a 8-ft antenna in my 18-ft boat. I have a feeling that a 8-ft antenna is just too long. If I mount it in the front rail of the T-top and set the antenna at a 45-degree angle toward the stern, the 8-ft antenna will still stick out covering the entire deck in the stern of my boat. This is going to be a problem if I want to cast from the deck in the stern of my boat because my fishing rod "may" hit the antenna. A 3-ft antenna that is pointing straight up will not have this problem. A 3-ft antenna mounted on the T-top will be as much as 9-ft above the water level. According to this formula: range-in-miles = square-root-of-height-above-water-in-feet x 1.42 I should expect to get the range of up to 4.26 miles. This seems to be more than enough because I will be boating and fishing near the shore (not more than a couple miles from the shore), and the coast guard with their very tall antenna should be able to reach me. OK, seem like I should get a 3-ft 3dB antenna. Jay Chan |
#10
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posted to rec.boats
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![]() wrote in message oups.com... NOYB wrote: "Wayne.B" wrote in message ... On 13 Jan 2006 09:56:30 -0800, " wrote: According to post in this newsgroup, we need a metal plate for grounding if we use a 3dB antenna, and a fiberglass boat doesn't have it. My boat is a fiberglass boat. What's the alternative? Does this mean that I cannot use 3dB antenna? There is no need for a ground with a VHF antenna. Either the 3 db or 6 db antenna will be adequate for near shore coastal operation. I'm with Wayne on this one. The dB rating plays a relatively minor role in the distance the signal travels. The height of the transmitting antenna plays a larger role. But the height of the receiving antenna is the most important element. Example: A 3' antenna mounted on the top of the gunwale of a small boat might be 5' above the water line. It can travel only 5 miles to another antenna that is only 5' off the water...but can travel 15 miles to an antenna that is 100' high (like at a Coast Guard station). An 8' antenna mounted on the same gunnel can travel 9 miles to another antenna that is only 5' off the water (big difference!), but only travels 18 miles to that 100' antenna (a not so big difference from the 3' antenna). If the CG antenna is 250' above sea level (mounted on a tower on a mountain for example), the 3' antenna can travel 23 miles...and the 8' travels 25 miles. So the question is... Who do you want to call with that radio? Another boat within 5 miles? Then either antenna is fine. The Coast Guard when you're 10-15 miles from shore? Then either antenna is fine once again. Here's a good link to explain this further: http://www.yachtworks.net/Store/antennas.htm Thanks for the explanation of the reason why a 3-ft 3dB antenna may be all I need. I go home and check the possible location for a 8-ft antenna in my 18-ft boat. I have a feeling that a 8-ft antenna is just too long. If I mount it in the front rail of the T-top and set the antenna at a 45-degree angle toward the stern, the 8-ft antenna will still stick out covering the entire deck in the stern of my boat. This is going to be a problem if I want to cast from the deck in the stern of my boat because my fishing rod "may" hit the antenna. A 3-ft antenna that is pointing straight up will not have this problem. A 3-ft antenna mounted on the T-top will be as much as 9-ft above the water level. According to this formula: range-in-miles = square-root-of-height-above-water-in-feet x 1.42 I should expect to get the range of up to 4.26 miles. But that's only to reach another antenna that is right at the level of the water. If there were another boat with an antenna 9' above the water, you'd carry at least twice that distance. |
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