VHF Antennas

Great article, and info. I have seen some of the Morad antennas around. They will be what I replace my Shakeys with if/when that happens. My 8ft glass is a Commrod and it has tested and performed well. I am a firm believer in having good antennas to get out (and in) good radio performance.

Harvey
SleepyC :moon

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Regarding the LED light issue with AIS and VHF, I've checked mine and found no problem. I suspect most of us on our C-Dory's are not going to experience any issues... Colby
 
colbysmith":2aaw5l7q said:
Regarding the LED light issue with AIS and VHF, I've checked mine and found no problem. I suspect most of us on our C-Dory's are not going to experience any issues... Colby
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Colby, it depends on the LED lights, (Brand) that are installed, and if they are on or off when the VHF is being used.

One issue that has not been mentioned is the proximity of the antennas one to another. That was my biggest concern when starting to add antennas. Optimally they would be 8 feet apart, and as we know, the C-Dory is not a boat with that kind of acreage readily available. I was able to scrape almost 4 feet between each, (I have 3, forward port and stbd and aft on the port side,) and that covers 3 VHF's and the AIS.

Harvey
SleepyC :moon

January_2010_344.thumb.jpg
 
hardee":1ycf5xow said:
One issue that has not been mentioned is the proximity of the antennas one to another. That was my biggest concern when starting to add antennas. Optimally they would be 8 feet apart, and as we know, the C-Dory is not a boat with that kind of acreage readily available. I was able to scrape almost 4 feet between each, (I have 3, forward port and stbd and aft on the port side,) and that covers 3 VHF's and the AIS.

Harvey
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NMEA publication on interference of various antennas, other metal objects, including horizontal as well as vertical spacing.

The NMEA gives 4 foot separation--I have found that on both sides of the cabin or radar arch is adequate. One must also avoid putting many other antennas in the radar beam. (Probably less with the new digital antennas, but some early GPS antennas were damaged by radar frequency waves.)
 
Well, In changing out antenna's I managed to damage the good one I was keeping on the boat, so the new 5225XT went to replace that one. (Which was the same model.) SO, I still have the cheaper antenna on the boat and once things warm up again and we dig out from all the snow coming (Polar vortex. Minus 50-60 degree windchills next week, with 8-12" of snow forecast for Monday. It may be a while before things warm up again.) I'm now looking at Shakespears new Quick Connect 8' antenna and wondering if anyone has experience with it.

Colby
 
colbysmith":2flfdz34 said:
Well, In changing out antenna's I managed to damage the good one I was keeping on the boat, so the new 5225XT went to replace that one. (Which was the same model.) SO, I still have the cheaper antenna on the boat and once things warm up again and we dig out from all the snow coming (Polar vortex. Minus 50-60 degree windchills next week, with 8-12" of snow forecast for Monday. It may be a while before things warm up again.) I'm now looking at Shakespears new Quick Connect 8' antenna and wondering if anyone has experience with it.

Colby
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Gotta love that global warming :wink: :mrgreen:

good luck on your project.
 
Also, is anybody using the Morad 9120 "hot rod" antenna? Is that the one you have Bob? How tall is that antenna.. I'm seeing some descriptions that say 86.75", but others that say 4 ft. Thanks. Colby
 
Well, I'd like to point out that both Shakespeare and Moorad build 6 dB antennas. And 6 dB is 6 dB whether the antenna is cheap or expensive, good or bad. It's measured performance.

The Moorad discussed in Slowboat is 6 dB and 4 1/2 feet tall, replacing a Shakespeare which has 3 dB and is 4 feet tall. Then Slowboat added a 2 foot extension so the installed length of the Moorad is 6 1/2 feet. So the final cost is $190 for a durable good 6 dB antenna.

Shakespeare has several VHF 6 dB antennas, all 8 foot tall. The prices at WM range from $80 to $95 thru $130 and $230 up to $300. I don't know what you get for $300, but it better be good.

I bought the cheap Shakespeare, which quickly broke and then found out the more expensive antennas are built better. Since I remove the antenna for trailering, I poped for the good one but I don't expect better VHF performance.

Also the co-ax lead in should be low loss, but for a C-Dory (any size) the run isn't very long. So, don't count on any performance increase on that account. The connectors need to be good and Bob has several posts on how to solder them.

My conclusion is that even the cheap 6 dB antennas deliver full performance; they just don't last as long if you beat them up.

Boris
 
Morad 9120 "hot rod" antenna? Is that the one you have Bob? How tall is that antenna..
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Yes Colby that is the antenna I am using on one of my radios. I probably will eventually replace the other, which is a 4'--not sure of the brand--it was on the boat.

The antennas are on top of the radar arch, so the base is over about 18" above the cabin top to start with. I did not add a base extension--but have in some other boats. The antenna its self is about 54 1/2" long. (including SS whip). Just making a guess but about 13 feet off the water at the tip.

The difference between the "quality" and "cheap" is a multitude of factors, from the materials of the casing, the quality of wire used, if crimped or soldered, plated fittings, quality of coax, if mini fittings are used, even the finish on the outside (Gel coat, two part urethane paint, or powder coating. Generally the more costly antennas will perform slightly better after a year of use; less corrosion, etc. A lot of the information is anecdotal. For example when I was cruising offshore and using a number of different antennas on 15 meter to 80 meter ham bands, I would rely on "signal strength" and intelligibility or quality of signal received by another ham operator thousands of miles away. There were lots of variables. But certain antennas performed better consistently on my particular boat. These antennas were much different physically than the VHF which is in the 156 +/- MHz frequency range. Propagation was entirely different. But the quality antennas performed better.
 
I'm liking the idea of having an antenna that has a cable connection at the antenna, rather than the ones that are hardwired to the antenna. Just to be able to remove the antenna easier, or to replace it if it gets broken. The Shakespeare QC-8 requires a special mount with the connector in that. What I like about the Morad, now that I have looked at them, is they can mount on a regular ratchet mount, with of course their M-91 adaptor. Price wise, I found a dealer where I can get the antenna for $138 and the adaptor for $32. Just a little more pricey than the Shakespeare 5225 XT regular antenna. The Shakespeare QC-8 would be about $79 and it's special ratchet mount another $50. I really don't want to lose the height of 8' above my rooftop where my antenna mounts. So if the Morad is only 4.5 feet, then there is more expense to get the extension stanchions. However, the 5225 xt has worked well for me, and it's not that hard to change out when they break. However, they can not be easily taken off and placed back on routinely. Colby
 
colbysmith":2gexast5 said:
I'm liking the idea of having an antenna that has a cable connection at the antenna, rather than the ones that are hardwired to the antenna. Just to be able to remove the antenna easier, or to replace it if it gets broken. The Shakespeare QC-8 requires a special mount with the connector in that. What I like about the Morad, now that I have looked at them, is they can mount on a regular ratchet mount, with of course their M-91 adaptor. Price wise, I found a dealer where I can get the antenna for $138 and the adaptor for $32. Just a little more pricey than the Shakespeare 5225 XT regular antenna. The Shakespeare QC-8 would be about $79 and it's special ratchet mount another $50. I really don't want to lose the height of 8' above my rooftop where my antenna mounts. So if the Morad is only 4.5 feet, then there is more expense to get the extension stanchions. However, the 5225 xt has worked well for me, and it's not that hard to change out when they break. However, they can not be easily taken off and placed back on routinely. Colby
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How often do you expect the antenna to break? Mine has been on the boat for 10 years and hasn't broken yet, even when my wife used it to retrieve the boat when it was being blown away from the dock (did bend the mount though). Seems that the Shakespeare FG antenna is stronger than the SS mount.

If my antenna ever breaks, I may decide to change it out to the connector type. but I'm not about to do anything with it unless I need to (like if I hit a bridge or something).
 
My last 2 never broke the cable simple rotted off where it enters the antenna. I now cover all my exposed wires with tha black flexable slit conduit to protect the wire from the sun.
 
I really don't want to lose the height of 8' above my rooftop where my antenna mounts. So if the Morad is only 4.5 feet,
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The antenna height is a bit over hyped on small craft. Let's say that we have two boats with the antenna height at 12 feet off the water. VHF radio waves are basically line of sight. The radio horizon (due to curvature of the earth) is 5 miles for each boat--and the total range is 10 miles. Increasing one boat to 16 feet (adding 4 feet) gives that boat a radio horizon of 6 miles, and the total range is only 11 miles. You have gained one mile of range, by increasing the height of the antenna 4 feet. (There is an exception and that is "Tropospheric Ducting". I have clearly talked to US naval Vessels which were over 350 miles away at sea--via ducting.)

The more expensive 8' fiberglass antennas bay have several radiating elements: The cheapest ones, just have wire going up the lowest part of the fiberglass tube.
 
How often do you expect the antenna to break?
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Trailering over 15,000 miles a year, it only takes one tree branch and not having the antenna's all the way down to break them... I got two, two years ago, within a month! :cry: (One of those was a tree right next to a narrow ramp, the other time stopping locally (where many times I only have the antenna's part way down) parking to eat and catching the limb as I backed up to pull out...

You have gained one mile of range, by increasing the height of the antenna 4 feet.
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Just that extra mile could make a difference! So unless the 4' antenna has sufficient increased performance over the 8 foot to work the same distance, that extra mile does matter to me.

Colby
 
Thanks Boris. Looks like the winner continues to be the Shakespear 5225 XT. I've been happy with that antenna, so think that is the one I'll stick with. Colby
 
colbysmith":2kx3xet1 said:
How often do you expect the antenna to break?
Click to expand...

Trailering over 15,000 miles a year, it only takes one tree branch and not having the antenna's all the way down to break them... I got two, two years ago, within a month! :cry: (One of those was a tree right next to a narrow ramp, the other time stopping locally (where many times I only have the antenna's part way down) parking to eat and catching the limb as I backed up to pull out...

You have gained one mile of range, by increasing the height of the antenna 4 feet.
Click to expand...

Just that extra mile could make a difference! So unless the 4' antenna has sufficient increased performance over the 8 foot to work the same distance, that extra mile does matter to me.

Colby
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My antenneas are beteween 12 to 14 years old. The oldest is an 8ft FG Commrod. It came down with a BANG on day after about 3 hours of pounding through 3-5 foot waves on the nose. Scared the c%@p out of me at the time. The ratchet had loosened. I did a quick tie down to the roof and continued, then into calmer water, and into Lagoon Cove for fuel. Docked and assessed the damage -- none. Put it back up and it checked out ok. Still does a nearly 1:1.5 SWR.

The other 2 antennaes are both base loaded Shakeys, one on an extension, one not. All 3 are layed down and secured, (the tips tied to the roof top hand rails) before the boat is towed from the launch site, and often before the boat even goes onto the trailer.

Harvey
SleepyC :moon
 
My antenna lies on the roof inside one of the roof rails. It goes up after the boat is launched and comes down before it is recovered. My antenna also carries the flag so it is fairly noticeable.

My antenna has also come down a few times because the ratchet loosens. Makes a lot of noise, but doesn't hurt anything (so far).
 
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