VHF Antenna Height

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offduty5

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Just installed a t top on my 1800 CC. Looking at Shakespeare 4 or 8 foot antenna. I only will go 15 to 20 miles offshore. I researched what to buy , model, ferrule, finish and connection. Any help would be appreciated.
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pelagic2530

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If you're putting it on a T-top, no reason to not go with an 8' antenna. You'll get a longer range and better reception at short range.

If you're worried about storage or stowing the antenna in the down position, Shakespeare makes QuickConnect models that allow you to unscrew the aerial from the mounting base without needing to disconnect any of the coax.
 

GoodChance

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The difference in range between a 4ft and 8ft antenna is negligible. Per the VHF antenna range calculators, you might get an additional 1-3miles of additional range with an 8ft antenna when 40-60 miles offshore. I typically use the 4ft antenna because they are easier to fold down and I am vain and down like 8ft, flimsy antenna flopping all over the place in a 2ft sea.

Additionally, I like the Digital (brand) antenna simply because their barrelled-end (the end that attaches to the back of the VHF radio) detaches very easily and screws back on. This is a nice feature when trying to "fish" the VHF antenna cable through your t-top pipework. You can do the same thing with a Shakespeare antenna but their barrel-end is much harder to install/uninstall
 

Swatski

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The difference in range between a 4ft and 8ft antenna is negligible. Per the VHF antenna range calculators, you might get an additional 1-3miles of additional range with an 8ft antenna when 40-60 miles offshore. I typically use the 4ft antenna because they are easier to fold down and I am vain and down like 8ft, flimsy antenna flopping all over the place in a 2ft sea.

Additionally, I like the Digital (brand) antenna simply because their barrelled-end (the end that attaches to the back of the VHF radio) detaches very easily and screws back on. This is a nice feature when trying to "fish" the VHF antenna cable through your t-top pipework. You can do the same thing with a Shakespeare antenna but their barrel-end is much harder to install/uninstall
That is only correct, for the most part, if you consider strength of signal and projection over flat plane ONLY (in other words - over short distance); however, if considering the Earth's curvature - a longer antenna will always give you MORE RANGE. For various reasons it is difficult to exceed 20-25 mile effective range radius but you will not get even close to that maximum possible distance/range with a short antenna mounted low.

1614205532212.png
 

Brent

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Look at Digital Antennas, too. High quality
Easy coax connector to mast. Easier to replace. 8 ft length is common but there are longer Antennas. Read info on Shakespeare and Digital web sites
Some radios are better than other. And wiring is important with good connrctiondy. You don't need the inline fuse if connected to a fuse panel
You can't beat an high end Standard Horizon or Icom radio. Wiring is very important, too. Remove excess coax cable
 
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warthog5

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Digital 529 is what I use [it's 8ft] ....Why? Because of the custom cable end that eliminates soldering. This is also handy and makes the job faster when it's time to replace the antenna......Why would you need to replace the antenna? Because someone forgot to lower it as you towed down the road......Happens all the time. Personally I use the Digital 529VB [Black]
 

Andy

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That is only correct, for the most part, if you consider strength of signal and projection over flat plane ONLY (in other words - over short distance); however, if considering the Earth's curvature - a longer antenna will always give you MORE RANGE. For various reasons it is difficult to exceed 20-25 mile effective range radius but you will not get even close to that maximum possible distance/range with a short antenna mounted low.

View attachment 27835
Agree with 'the higher the antenna the better', especially on a non-rocking/rolling boat. Our previous boat had two VHF radios. One attached to an 8', 6 db antenna, mounted on the flybridge with the base of the antenna 11' above the water. (effective height, 19' tall). The other radio was hooked to a Shakespeare (4018) two-piece 19' tall 9db antenna where the base was also mounted 11' above the water (effective height, 30' tall/above the water). I could communicate between the Pungo Creek area of NC to Silver Lake on Ocracoke Island to a friends boat that had a similar 9 db set up on his boat. (We could NOT with the 8' 6db). The distance, (the way the crow flies) between Pungo Creek and Ocracoke is about 46 miles. Under certain conditions VHF can 'skip' and give a longer range than even the direct line of sight antenna-to- antenna graphics depict.; especially with the 9 db that concentrates the signal to the horizon. 9 db is a great way to go, but on rocking/rolling smaller boats, the 9 db signal is often just lost/directed into the water, and/or directed into outer space! On our Parker-Sized boats, the 8' 6db is a good compromise. We could use a 9 db, but it would work best, only on calm days.
1614267326367.png
 
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Pescador4ever

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Offduty, I have an 1801 CC with a Shakespeare 5400-TX Galaxy Little Giant. Mine is mounted on my railing around my console (don’t have a T-Top). I’ve gotten 50+ miles of range with it. Like most antennas I’ve seen, you’ll need to run the cable to your radio then terminate the UHF (yes, sounds weird because it’s a VHF antenna) connector at the end. Lots of options out there, I do run offshore and everwhere else with zero issues reaching out to somebody.
 

Fishaddict

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I am about to buy and install an antenna on hard top 1801. I think to go with small whip style antenna. What model would you recommend?
 

warthog5

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I think to go with small whip style antenna.
Your not talking one of those 3ft sailboat antennas......are you?

A 18ft boat with no T top is always hard to figure out......But do NOT waste time and $ on a Lil 3ft whip.....Been there done that.....You want a ratchet mount on console and lay it forward when not in use.
 

Andy

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Your not talking one of those 3ft sailboat antennas......are you?

A 18ft boat with no T top is always hard to figure out......But do NOT waste time and $ on a Lil 3ft whip.....Been there done that.....You want a ratchet mount on console and lay it forward when not in use.
I'm with Warthog! I have many friends over the years that wasted time and $$ with a short, 3db whip antenna. They can sometimes RECEIVE signals from a great distance (say, from another boat or USCG base-station, and who are NOT using a 3db!), but your 'sending/broadcast' signal will fall short. I've been told many times, "Hey, I heard you calling me, why did you (meaning me!) not respond?!" The simple answer is, I didn't respond because it was impossible to receive their weak, short-range, 3db signal. I didn't hear them. A 3db will do a little better mounted 60 feet in the air on top of a sailboat mast, but that's just because of the height; the signal is still a weak 3db. (Sailboats use them because if they had higher db antennas, most of the signal would be shot into the water or into outer space when healed over).
 
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Fishaddict

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My boat has hardtop t top. I am worried about extra dynamic loads on a skinny sandwich of the top. I will be using it for emergency coast guard communication. Athe there any light/short antennas better than others?
 

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warthog5

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Fishaddict.....Stop worrying.....Use a Shakespeare HD ratchet mount...Correct length bolts and acorn nuts on the underside....with a dab of locktite. .Use a Blue Seas Cable clam to route the coax thru.....

Emergency: Means I need Help NOW!
 

rseate

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My boat has hardtop t top. I am worried about extra dynamic loads on a skinny sandwich of the top. I will be using it for emergency coast guard communication. Athe there any light/short antennas better than others?
I’ve got the 8’ Shakespeare Mariner with their ratchet mount mounted to my fiberglass tee top. As Warthog said, use the correct bolts (I put a dab of 4200 under the mount) and you won’t have any problems.
 

pelagic2530

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My boat has hardtop t top. I am worried about extra dynamic loads on a skinny sandwich of the top. I will be using it for emergency coast guard communication. Athe there any light/short antennas better than others?
Another vote for the bigger antenna. You should absolutely not be looking at anything less than a 4' aerial, preferably 8'. Look at the underside of your T-top; very likely you have mounting plates designed specifically for the mounting of antenna bases. If not, use a backing plate made from starboard or fiberglass and thru-bolt the mount. If you're really worried about it, you can fashion a mount that spans one of the T-top tubes, or install a product like this: Universal Mounting Bracket
 

offduty5

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Went with warthogs advise.... bought the 529.... thanks for everything... will post when installed
 

Pescador4ever

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Don’t forget to stow it before you trailer your boat anywhere. Sounds common sense, but sometimes sense isn’t so common.
 

GoodChance

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VHF radio transmission distance is based upon 1) curvature of the Earth, 2) height of the receiving antenna, and 3) height of the transmission antenna.

The additional range offered by an 8ft antenna is about 1mile (or less) than a 4ft antenna) assuming both are mounted to a cabin or T-Top 8ft above the water.

Here is the calculator ...... CEPD Tools - Transmission Calculators
 

pelagic2530

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VHF radio transmission distance is based upon 1) curvature of the Earth, 2) height of the receiving antenna, and 3) height of the transmission antenna.

The additional range offered by an 8ft antenna is about 1mile (or less) than a 4ft antenna) assuming both are mounted to a cabin or T-Top 8ft above the water.

Here is the calculator ...... CEPD Tools - Transmission Calculators
Of note, most 4' antennas are 3 - 4.5db antennas, compared to the 8' antenna's 6db rating. Andy's chart above illustrates what the effect of a lower decibel rating is in terms of radiated energy. Both the energy and the height of your antenna will affect the range of your transmission.
 

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