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4ft VHF antenna vs. 8ft antenna VHF

Old 07-22-2012, 08:01 AM
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Default 4ft VHF antenna vs. 8ft antenna VHF

I have to replace my 8ft. VHF antenna and was thinking about using the 4ft. little giant instead of another 8ft. I know antenna's transmit using "line of sight" but was wondering if the components are better in a 4ft. antenna then will it transmit just as far?

I would get another 8ft. but the little giant looks better constructed and my boat is rack stored so it's easier to retract up and down. The 8ft would also loosen the bolts on the antenna stand from time to time.

Thanks guys!
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Old 07-22-2012, 11:12 AM
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Generally speaking an 8 footer will give better performance over a 4 footer. That said, if you stay within 8-10 miles of shore, a 4 foot will suffice. If I was doing a 4 foot, I'd look at the Metz 3' SS, which works well.
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Old 07-22-2012, 09:34 PM
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Consider the Shakespeare Little giant has a 3dB gain rating whereas most 8 'ers have a 6dB gain. If your boat rocks a lot the 3 dB will have a more consistent radiating pattern/ transmission coverage but will not have the potential range of the flatter wider pattern of the 6dB antenna... if... the top of each is at the same height.

More info: http://reviews.ebay.com/VHF-Marine-R...00000000015940
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Old 07-22-2012, 09:48 PM
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4' less cuts down distance by about 1 to 2 miles less distance, all else being equal.
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Old 07-23-2012, 08:25 AM
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Originally Posted by Parthery View Post
Generally speaking an 8 footer will give better performance over a 4 footer. That said, if you stay within 8-10 miles of shore, a 4 foot will suffice. If I was doing a 4 foot, I'd look at the Metz 3' SS, which works well.
I do most of my boating out of the Miami, FL. area. When I am fishing offshore I travel 15 to 20 miles out every now and then but mostly between 5 and 10 miles out. My 8ft antenna wouldn't really pick up anything once I was 5 miles out or more. That's why I was wondering if the brand makes a difference even though you go shorter.

Originally Posted by TTaxi View Post
Consider the Shakespeare Little giant has a 3dB gain rating whereas most 8 'ers have a 6dB gain. If your boat rocks a lot the 3 dB will have a more consistent radiating pattern/ transmission coverage but will not have the potential range of the flatter wider pattern of the 6dB antenna... if... the top of each is at the same height.

More info: http://reviews.ebay.com/VHF-Marine-R...00000000015940
My old antenna was probably a 3dB based on the range I would get. I am not really sure though because the outside coating was in bad shape and I couldn't see a brand name. This is for a 32ft. center console so it rocks when offshore.

Originally Posted by SaltyG View Post
4' less cuts down distance by about 1 to 2 miles less distance, all else being equal.
What I found through research was this formula: Max mounting height + Antenna Height = X . Then X times 1.42 = range
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Old 07-23-2012, 09:04 AM
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Get a decent 8'. Either the Shakespeare 5225 or a Digital 529. Should be a few bucks either side of $125 or so.
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Old 07-23-2012, 09:52 AM
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Size matters.
By the way, something very wrong with your previous 8' or it's connections, should have got lot more than that.
Pay attention to your connection with your new fit, it's the only time I call a pro in for electronics, good soldered connector & put on a test meter after to check it, worth it to be sure it's spot on.
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Old 07-23-2012, 12:12 PM
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"My old antenna was probably a 3dB based on the range I would get. I am not really sure though because the outside coating was in bad shape and I couldn't see a brand name. This is for a 32ft. center console so it rocks when offshore."

It was most likely an 8db gain antenna when new but if the outer surface was in bad shape that is an indicator it may not have been very high quality in the 1st place and the inner radiating element may have dislodged fallen. Better antennas have sturdier parts for more reliable perfomance over longer life.

If you are transmitting from a rocking drifting or slow moving boat to a station in a known direction, a tip to think about is best range will be perpindicular to the side to side rocking . So if you can aim the boat to or from the distant station , with antenna mounted plumb, you maximize chance of contact. If you are running at speed in rough water with bow bucking , best range may be off your beam.

You just want to minimize signal loss aimed at sky or water. The cool guys with raked antennas are not doing their tranception any favors.
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Old 07-23-2012, 03:12 PM
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Interesting to see how many of the USCG boats are using 4' antennas...don't they even read THT?
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Old 07-23-2012, 04:40 PM
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I have an 8' mounted on my radar arch so it gets up there pretty high. We were out at Block Island on several different trips and I was receiving USCG transmissions from Maryland. That is a long ways away. Now I don't think I could transmit that far obviously but I was picking up their transmission like they were right on the main land of RI. So if it were me i would get a good quality 8' and mount it high. Make sure you install it properly or get someone to do it for you and enjoy trouble free VHF performance you can count on.
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Old 07-23-2012, 05:36 PM
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All antenna gain comes from reducing the radiation pattern and concentrating the radiation into a main lobe. An antenna only has gain when its main lobe is pointed at the other station in the circuit.

Antenna gain is only something that is claimed. There are no certifications of the measured gain provided. It is common for antennas rated as "3-dB" Marine gain--which is actually no gain at all--to have better performance than antennas rated as "6-db" Marine gain--which is probably about a real 3-dB of gain. No one audits these claims.

An antenna with higher gain only shows an advantage when

--the main lobe is oriented at the distant station

--the path is marginal so that extra gain helps

--the antenna actually produces the gain it is claimed to have

If everything is perfect, then 3-dB of gain will extend the path at a marginal signal level by about 20-percent at best. For a more rigorous analysis, see

http://continuouswave.com/whaler/ref.../pathLoss.html

A broken 8-foot antenna does not work very well compared to a working 4-foot antenna.
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Old 07-23-2012, 05:57 PM
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When you are talking to the CG's 250' high antenna it is not going to make any difference whether your antenna is 4 or 8 feet.

Good hardware and a proper installation are far more important than the height.

In rough seas, or if the boat is heeling, or if the antenna is folded partway, an 8 footer will not perform as well as a 4 footer.
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Old 07-23-2012, 09:56 PM
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Originally Posted by Karl in NY View Post
Interesting to see how many of the USCG boats are using 4' antennas...don't they even read THT?
USCG boats routinely encounter conditions that would snap a longer f/g antenna off either when falling off waves or from solid green water over the top. Most of the rest of us do not choose to go out when the Coasties have to. When needed, they also may have comms relayed to them from the base high-towers as mentioned above, plus , I wonder if their onboard fixed sets are limited to 25W? Obviously the base is not.
I also noted that the Metz antenna site indicates many of those USCG metal whip antennas were designed for the S&R boat VHF direction-finding sets , which may or may not be used in conjunction with a transmitting VHF on the same antenna.
http://www.metzcommunication.com/ima...heetforweb.jpg

Not saying the Metz antennas are bad by any means.
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Old 07-24-2012, 05:38 AM
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Originally Posted by Parthery View Post
Get a decent 8'. Either the Shakespeare 5225 or a Digital 529. Should be a few bucks either side of $125 or so.
x 2 and then make sure the connection is made correctly. A weak connection will have impact on your signal.
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Old 07-24-2012, 09:39 AM
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I always hope that people are joking when this subject comes up, which it does on a sadly frequent basis. If you really want to read the truth behind the question, just search for "VHF antenna".
VHF is line of sight. If you want to talk over the horizon, be taller. (I was going to say get higher, but....)
Certain cloud conditions can trap the signal from very powerful radios, and funnel it a thousand miles away, but that won't happen when you need it.
All fixed mount VHF radios can transmit at 25 watts. It's the law. Some can sound better than others, but the amount of power is limited. There can be a lot of variation in the radiating pattern and quality of construction various marine radios, but that doesn't mean their signal can bend over the horizon and be heard by those inclined to come save your butt when you get in trouble. Like my ex-wife, some people believe that the more something costs, the better it is at doing something. I can't help you there; my favorite comedian notes "you can't fix stupid."
The "I'm too lazy to fold my antenna" crowd have always come up with a number of semi-scientific excuses for using a 3 or 4 foot sailboat antenna on a T-top. This is a lot like the thinking that goes into winning the Darwin Award, an effective way of weeding out the gene pool. By that I mean boaters who find themselves beyond the radio horizon of their 4 foot antenna might not be around to breed after getting into trouble on the water.
So, if just for the sake of the Malthusian dilemma, and particularly if you have already bred, get an eight foot antenna, and you can go home and put the little darlin's through college.
If you read some of the previous threads on the same topic you will discover that Shakespeare's cheapest antenna, the one so many connoisseurs turn their nose up at, will last twelve years if minimally cared for, and cost a third of that pretty little 3 footer.

Last edited by sandyda; 07-24-2012 at 09:40 AM. Reason: the lilly needed gilding
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Old 07-24-2012, 10:08 AM
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Originally Posted by sandyda
I always hope that people are joking when this subject comes up, which it does on a sadly frequent basis. If you really want to read the truth behind the question, just search for "VHF antenna".
VHF is line of sight. If you want to talk over the horizon, be taller. (I was going to say get higher, but....)
Certain cloud conditions can trap the signal from very powerful radios, and funnel it a thousand miles away, but that won't happen when you need it.
All fixed mount VHF radios can transmit at 25 watts. It's the law. Some can sound better than others, but the amount of power is limited. There can be a lot of variation in the radiating pattern and quality of construction various marine radios, but that doesn't mean their signal can bend over the horizon and be heard by those inclined to come save your butt when you get in trouble. Like my ex-wife, some people believe that the more something costs, the better it is at doing something. I can't help you there; my favorite comedian notes "you can't fix stupid."
The "I'm too lazy to fold my antenna" crowd have always come up with a number of semi-scientific excuses for using a 3 or 4 foot sailboat antenna on a T-top. This is a lot like the thinking that goes into winning the Darwin Award, an effective way of weeding out the gene pool. By that I mean boaters who find themselves beyond the radio horizon of their 4 foot antenna might not be around to breed after getting into trouble on the water.
So, if just for the sake of the Malthusian dilemma, and particularly if you have already bred, get an eight foot antenna, and you can go home and put the little darlin's through college.
If you read some of the previous threads on the same topic you will discover that Shakespeare's cheapest antenna, the one so many connoisseurs turn their nose up at, will last twelve years if minimally cared for, and cost a third of that pretty little 3 footer.
Isn't the suggestion that going with a 3 or 4 foot antenna is stupid and dangerous (warranting a "Darwin Award) a little ridiculous. It seems to me that given the modest height and distance advantage, which may be offset or negated because of the "narrow lobe in rocking seas" issue associated with higher gain, along with the multitude of other things that could go wrong when on the water, this is over-exaggeration of the highest order.
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Old 07-24-2012, 10:21 AM
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^ what saxe point said.

Frankly, where I boat, I can reliably hit USCG with a handheld on the 1 watt setting, due to their antenna being 4400 ft. above MSL. They cover the whole 125 mile long lake from that one tower.

That also parallels my terrestrial experience on the 144 mHz ham band using mountain top repeaters...
generally a 4 state coverage area with 3 watts and a 6" antenna.
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Old 07-24-2012, 11:47 AM
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I find it interesting that people vigorously debate VHF antenna issues that may make a difference of a few miles at best. Yet no one ever talks about SSB (MF HF), which, as I understand it, has frequencies that are monitored by the USCG. I also understand that SSB distances range from hundreds to thousands of miles. If the limits of VHF range are a meaningful problem, isn't SSB (and/or satellite phone) the easy answers. Why so little attention to SSB?
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Old 07-24-2012, 12:14 PM
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Originally Posted by saxe point View Post
Why so little attention to SSB?
Cause you need a 16' antenna for starters, not many small boats in our size class can support a 16'er. Then throw in the $2k worth of equipment required to go with the 16'er.

Incedently, to clear up the orig. issue, the difference between a 4' and 8' antenna is 4'!!!! 8 - 4 = 4!! What's wrong with you people!!
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Old 07-24-2012, 12:57 PM
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Originally Posted by Birdman

Incedently, to clear up the orig. issue, the difference between a 4' and 8' antenna is 4'!!!! 8 - 4 = 4!! What's wrong with you people!!
That's pretty picayune, given that there are so few 4 foot antennas available compared to 3 footers, and given that most (Digital's being the exception) are 3db antennas just like the 3 footers. Lighten up my friend.
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