VHF antennas banging on bimini frame

[HeadedToTexas]

Yes, those VHF antennas look cool, but most wind gusts create enough movement in the bimini frame to bang against the antennas. The pilothouse roof amplifies the sound to the point that it's all I hear. Well, perhaps that's a bit dramatic, but it feels like there is a better answer.

First, why wouldn't those antennas be better off on the radar mast? Any reason not to move them up there?

And second, as a Great Lakes cruiser with Loop aspirations, just how much reach will I need from my VHF radios? In my limited experience between Grand Haven, MI and Sandusky, OH, the handheld VHF with its low output and small antenna do just fine. Could my more permanent radios get by with smaller antennas?

 

[backinblue]

Yes, smaller should be fine and actually have advantages in some conditions. Your maximum range may be less, but that doesn't sound like it should be an issue for you. Here's a good article on the subject.

https://www.powerandmotoryacht.com/...st, and most obvious,alone being a major plus.

 

[psneeld]

You might be able to slip a piece of pipe insulation over the antenna....has worked many places before.

The antennas might be better on the mast but there are other considerations like ease to lower if roller than the mast or just how they look to you for appearance....

I don't like going smaller on the antenna size because loss of gain...sure the theorists say its all about height, but your radio signal may need to overcome weaker, closer signals when you need to get through to someone. There can be a lot of trash radio when doing the loop in some areas, plus the power can help overcome line of sight issues when traveling Inland waters.

 

[wkearney99]

You might be able to slip a piece of pipe insulation over the antenna....has worked many places before.

Pool noodles are also an idea. There are usually different sizes, some of the smaller diameter might be a colorful option. Throw some zipties around the ends if you want to keep in tight.

 

[rslifkin]

If you're really concerned for the loop, wire 2 antennas for each radio. 1 big, tall one, one short one. When in height constrained areas where you need the big antennas down, switch to the short ones.

 

[HeadedToTexas]

I am using short sections of pool noodles now. They do a decent job of silencing the noise and the price is certainly right.

 

[kthoennes]

Pool noodles are very useful. We also use the big ones as snubbers or stand-offs for our dinghy off the swim step. Run the short mooring lines through the centers. My son uses short sections of noodles on his kayak paddle which for some silly reason doesn't float otherwise.

 

[HeadedToTexas]

Yes, smaller should be fine and actually have advantages in some conditions. Your maximum range may be less, but that doesn't sound like it should be an issue for you. Here's a good article on the subject.

https://www.powerandmotoryacht.com/...st, and most obvious,alone being a major plus.

Good article; thank you. Excessive rolling is never welcome or sought, but is largely unavoidable in the Great Lakes at times. Is that a reason to have 6 dB antennas? Most manufacturers seem to think so, but they are influenced by a variety of goals. Guess I am trying to validate the need for tall antennas with the experiences of TF users. How often are you using VHF at the limit of its range? How do you deal with the constant static of you do not squelch out the limit of its range? Isn't most VHF traffic between bridges, locks, and marinas? At trawler speeds, does that not mean just a few miles or so?

 

[backinblue]

Good article; thank you. Excessive rolling is never welcome or sought, but is largely unavoidable in the Great Lakes at times. Is that a reason to have 6 dB antennas? Most manufacturers seem to think so, but they are influenced by a variety of goals. Guess I am trying to validate the need for tall antennas with the experiences of TF users. How often are you using VHF at the limit of its range? How do you deal with the constant static of you do not squelch out the limit of its range? Isn't most VHF traffic between bridges, locks, and marinas? At trawler speeds, does that not mean just a few miles or so?

Many here have much more experience than me, but in my experience, I'm rarely talking to anyone that's more than a mile or 2 away. If I am, it's usually trying to reach a fellow boater, not out of any real boating need. A handheld would probably serve 95% of my needs, but my main setup has a 6db antenna and I've never wished I had more. Here's a good article and illustration why sometime less is more.

https://shakespeare-ce.com/marine/antenna-selector/

 

[psneeld]

I have both the 9db 17 foot and a 6db 8 foot on an extension.

If you need power to overcome useless chatter for an emergency or need the long range just to talk to someone....you will be glad you had the options.

Yes a handheld will work for bridges, locks and conflicting traffic.....but remember, Inland it is a powerful rescue tool.

Most boaters don't have the experience with radio to be a great judge....many do, but most don't. Having been on both sides of emergency or assistance calls....I can say that if you think safety is at all worth worrying about....no matter how big or small the antenna...make sure on Inland waters (not some big lake, but winding, tree lined river) you can still punch out and receive as far as you think necessary.

I often tested my 6db gain against my 9 db gain antenna with the automated radio check playback along the ICW and the difference was certainly convincing.

 

[backinblue]

I have both the 9db 17 foot and a 6db 8 foot on an extension.

If you need power to overcome useless chatter for an emergency or need the long range just to talk to someone....you will be glad you had the options.

Yes a handheld will work for bridges, locks and conflicting traffic.....but remember, Inland it is a powerful rescue tool.

Most boaters don't have the experience with radio to be a great judge....many do, but most don't. Having been on both sides of emergency or assistance calls....I can say that if you think safety is at all worth worrying about....no matter how big or small the antenna...make sure on Inland waters (not some big lake, but winding, tree lined river) you can still punch out and receive as far as you think necessary.

I often tested my 6db gain against my 9 db gain antenna with the automated radio check playback along the ICW and the difference was certainly convincing.

I don't disagree with anything you have stated but you have to also understand the signal pattern of different antennas and in rough water the higher gain antenna may be sending a stronger signal but not being received because it is missing the target. In relatively calm waters like the ICW the higher gain will always win, but how far do you really need to reach out in that situation anyway?

 

[psneeld]

Well as I said before, there is theory and practical experience.

You also need to understand power isn't only about distance, its about a strong, clear signal getting through.

I wouldn't want to be without both.....Inland and offshore. Been there, done that.

 

[backinblue]

Well as I said before, there is theory and practical experience.

You also need to understand power isn't only about distance, its about a strong, clear signal getting through.

I wouldn't want to be without both.....Inland and offshore. Been there, done that.

I agree and happy for you that you can have both. But if a boat doesn't have that flexibility and you have to make a single choice (as I think the OP was asking) bigger might not necessarily be better.

 

[psneeld]

Unless its a dingy, I still recommend carrying the largest antenna you can fit (on his or your boat a 17 could be be installed) and a smaller you can switch to or just have a second radio hooked to it.

 

[koliver]

Instead of allowing the banging and cushioning it with foam, how about tying the antenna to the Bimini frame with a zap strap?

 

[psneeld]

Instead of allowing the banging and cushioning it with foam, how about tying the antenna to the Bimini frame with a zap strap?

Hard standoffs too can work...just hard to say what works without seeing the pieces and parts if they interact.

 

[Benthic2]

Most cell phone providers have coverage maps on their website. It might be worthwhile to check out your loop route and see how much of it is covered by cell phone. A great loop message board would probably have that info as well.

 

[psneeld]

While cel phones are great resources, they are in no way a substitute for VHF.

Read any publication by professional mariners or rescue people on the topic.

One of the cel phone experts here on TF one time said don't use the website coverage maps you need to get the detailed ones to really see accurate coverage.....and I believed him as my coverage all over the Eastern US has been far from what the general website maps show.

 

[FF]

Remember many bridges require all items that can be lowered to be lowered IF the boat will fit under the bridge with everything down.

Lots of road folks get unhappy at the delay caused by keeping up a Wonder Whip, and complain enough that bridges get opening times, instead of opening on demand.

 

[diver dave]

Antennas and random closeby metal don't make good friends. Antennas are loners. Use a VSWR meter and get the actual electronic story before you position the antenna near other metallic tubes.

 

[backinblue]

Agreed. I still don't see where the majority of boaters need more than a 6db antenna, in fact a 3db would probably never be a problem for the majority of us.

 

[sledge]

First, why wouldn't those antennas be better off on the radar mast? Any reason not to move them up there?

Lots of installers and even manufacturers will place a pair of antennas not for performance, but for aesthetics
if they're two VHFs operating simultaneously, say one for comm and one for AIS, it is good practice to keep them physically separated by at least one wavelength if possible. A wavelength in VHF band is about 6 feet. This helps keep one transmitter from saturating or interfering with the other receiver. I assume if you put them on the mast, they would be much closer to each other...?

 

[diver dave]

On my boat, I have almost 80' run of small coax to the antenna base. Antenna is 3dB gain. The tables show around a 5 to 6 dB LOSS in the cable. 6dB is a scalar factor of 4x. So, there is no effective gain in the transmit side of the system, and on receive, that loss translates into a much higher noise figure that what the radio itself is responsible. Even with that, the performance is great, due to the base of the antenna at 55'. Much better than my last powerboat with a 8 dB gain antenna, base 4' above seal level, and short coax run. It is important to realize the significance of higher ERP (effective radiated power) on the transmit side. Due to the use of FM, capture effect says that only the strongest signal wins. So, you have to have more ERP and/or height to force the distant receiver to hear YOU. Close in, power wins; but, towards the fringes, height will win. And yes, good thing we all are limited to 25Watts Tx power!
Ultimately, to work the distant fringes, height of both antennas, and an electrically quiet environment work well to get you range. Electrically quiet may mean turning the battery charger OFF, and maybe even the a/c units. I've seen otherwise good installations trashed by locally made hash.

 

[backinblue]

On my boat, I have almost 80' run of small coax to the antenna base. Antenna is 3dB gain. The tables show around a 5 to 6 dB LOSS in the cable. 6dB is a scalar factor of 4x. So, there is no effective gain in the transmit side of the system, and on receive, that loss translates into a much higher noise figure that what the radio itself is responsible. Even with that, the performance is great, due to the base of the antenna at 55'. Much better than my last powerboat with a 8 dB gain antenna, base 4' above seal level, and short coax run. It is important to realize the significance of higher ERP (effective radiated power) on the transmit side. Due to the use of FM, capture effect says that only the strongest signal wins. So, you have to have more ERP and/or height to force the distant receiver to hear YOU. Close in, power wins; but, towards the fringes, height will win. And yes, good thing we all are limited to 25Watts Tx power!
Ultimately, to work the distant fringes, height of both antennas, and an electrically quiet environment work well to get you range. Electrically quiet may mean turning the battery charger OFF, and maybe even the a/c units. I've seen otherwise good installations trashed by locally made hash.

Is the base of your antenna really 55' above the water?

 

[diver dave]

54.5' +/-

I have yet to actually touch it!

 

[backinblue]

Must be a good sized ship! Also, have you thought about replacing the long run of cable with something heavier? I'm guessing it might be difficult to access in some areas.

 

[diver dave]

Thinking of using RG9 or LM400UF next hauling.

 

[psneeld]

Practical experience trumps theory almost all the time.

Have any of you had VHF conversations over 50 miles?

How about 100 miles?

Theory says not possible or exceptional in most cases...... not in my experience. Its not a common thing but certain factors push past theory.

Sure, a handheld would be fine most of the time. Even 30 miles or so for USCG work much of the time. But when you need it...for the want of an antenna.....gonna chance it? People spend hundreds of dollars on overpriced butt connectors....wonder if they buy the best, most powerful antennas?

 

[diver dave]

The atmosphere, of course, is not a constant. More of a HF than VHF thing, but both are affected. So called “ducting” can take vhf signals well beyond the horizon. So will meteor scatter, but these are fairly exotic, short lasting events.

 

[backinblue]

Practical experience trumps theory almost all the time.

Have any of you had VHF conversations over 50 miles?

How about 100 miles?

Theory says not possible or exceptional in most cases...... not in my experience. Its not a common thing but certain factors push past theory.

Sure, a handheld would be fine most of the time. Even 30 miles or so for USCG work much of the time. But when you need it...for the want of an antenna.....gonna chance it? People spend hundreds of dollars on overpriced butt connectors....wonder if they buy the best, most powerful antennas?

Maybe you don't know all the theories? In theory, radio signals can "skip" off the atmosphere and travel hundreds of miles.

Correct, height is only one factor. This link below has a convenient tool to do some theoretical comparisons as well as a good illustration of antenna gain +/-. The biggest most powerful antenna will give you the longest range if the conditions are ideal, but it is not w/o its negatives, including bridge clearances. Not saying they are not needed for some, just that for most of us, we can do just fine with a smaller antenna.

https://shakespeare-ce.com/marine/antenna-selector/