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VHF question:

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AADIVER
Admiral

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USA
966 Posts

Initially Posted - 01/08/2006 : 23:58:16

What is the range difference between a masthead mounted antenna and a rail mounted antenna for a 20 watt VHF radio? My '01 wasn't equipped with the antenna option, nor did it have a VHF radio. It would be a lot less expensive to intall a rail mount than a masthead mount. Thanks for any input.

Frank Farmer
Long Beach, CA
aa.diver@verizon.net
http://mysite.verizon.net/aa.diver

PRETTY PENNY
'01 C-250 WK, Hull #558

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/09/2006 : 00:12:51

Frank,

An antenna mounted 5' above the water will have a range of 5 miles to another antenna mounted 5' above the water and an antenna mounted 30' above the water will have a range of 10 miles to that same 5' mounted antenna.

As the antenna height of the person on the other end is increased, the difference in range between the 5' and 30' local antenna becomes smaller.

Check out this link to [url="http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/selecvhf.htm"]Selecting a VHF Antenna[/url] from the West Marine Advisor.

Edited by - dlucier on 01/09/2006 00:14:09

AADIVER
Admiral

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USA
966 Posts

Response Posted - 01/09/2006 : 02:12:53

Well, if a 5 watt handheld radio only transmits the same distance as a rail mounted 20 watt radio, why pay the extra bucks for a rail mount and interior installed radio? No comprende, senor.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 01/09/2006 : 12:00:26

The advantage to the permanant mount involves remote speakers and mics, usability, etc. I have a handheld only and am less likely to turn it on than people with permanant radios with hardwired power.

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AADIVER
Admiral

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USA
966 Posts

Response Posted - 01/09/2006 : 12:59:50

So, in a worst case scenario, i.e. MAYDAY or PAN, a handheld transmission would be picked up by Coast Guard's powerful receivers...right? If so, all I need is a handheld and my cell phone...right? Hope so

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 01/09/2006 : 13:28:24

I had a 3 foot whip on top of my mast. I was not getting a good signal. I replaced it with a very good quality 8 foot antenna on my stern rail. Yesterday I was sailing out of San Diego and listening to conversations in Dana Point and Newport, 65 miles away

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britinusa
Web Editor

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USA
5404 Posts

Response Posted - 01/09/2006 : 18:35:15

The Critical issue is 'Line of Sight'
At sea level the horizon is about 12 miles away.
so no matter how strong the transmission, it won't be receieved beyond 12 miles between sea level mounted antennas,
So mouting the antenna higher up increases the 'line of sight' distance.
A strong receiver can pick up a much weaker signal if it can 'see' it. So spend both the bucks and time and put the antenna on the mast head.

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djn
Master Marine Consultant

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USA
1561 Posts

Response Posted - 01/09/2006 : 19:07:34

Hi Frank. Not to put to fine a point on it, a receiver is sensitive not powerful.....it does not seem important, but when you think of who can receive you, that is what the critical factor is. Transmitters are powerful or not. I went with a perminent mount because it makes me feel like a real sailor. Visions of capt. bly. AAHHRRRR! I have a mast head antenna but don't yet know how it performs, but I did read in one of these posts, that someone hooks their antenna lead to one of the side stays and it works very well. Cheers.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 01/09/2006 : 19:45:46

here is what I have
permanent mount, soon to be tied into the Am/FM speakers as an override. And, when I take a bolt of lightening and everything else is toast, the handheld in my bag.

Other ramblings of a mad man

Paul's post makes the most sense to me...not that it matters.
Frank Hopper also makes a good point, if its mounted, you don't need to get it out of the bag and would be more apt to leave it on...Good in theory, but mine is never on, which is why I plan on tying it in to my speakers for the amfm....which is almost always on playing sattelite radio or CD's.

Dennis --I hook my radio antenna to the stays, not my VHF. That is on a whip mounted at the very top of the mast. I don't recall anyone else mentioning that in the past few years...I could be wrong and will gladly sit corrected if that is the case.

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takokichi
Captain

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USA
321 Posts

Response Posted - 01/09/2006 : 20:00:42

Remember to put handheld in a pelican case lined with foil - faraday cage will prevent inductive current from ruining your back up.

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Tom Potter
Master Marine Consultant

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USA
1913 Posts

Response Posted - 01/09/2006 : 20:49:33

Go the extra steps and get yourself a good VHF with a mast mount antenna. Its better to "Have" than wish you "had".

Edited by - on

djn
Master Marine Consultant

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USA
1561 Posts

Response Posted - 01/09/2006 : 21:02:42

Hi Duane, as soon as I read your post, I remembered the conversation. We talked about the AM/FM going to the stays not the VHF. Thanks for the reminder. Cheers.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 01/09/2006 : 21:24:31

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by britinusa
 The Critical issue is 'Line of Sight'
At sea level the horizon is about 12 miles away.
so no matter how strong the transmission, it won't be receieved beyond 12 miles between sea level mounted antennas,
<hr height="1" noshade id="quote"></blockquote id="quote">
Not quite true... Just as waves in the water "wrap around" a shore, the waves from a VHF wrap around the horizon up to a point. That's why Jim's radio is receiving distant signals, although his transmissions might not get out quite that far. Shorter wavelengths (AM, SW, SSB...) reflect off the ionoshpere, so with enough power (a lot more than 20 watts), they can travel much further--thus the distinction from "line-of-sight" (roughly) transmissions. But if all boaters could do that, nobody would ever be able to understand anything!

The main advantage of VHF over cell phones is your ability to get help from a nearby boater without knowing his phone number. Boaters 25 miles away are not much help to you. Coastal sailors almost always have cell phone reception for calling the Coast Guard or other on-shore help. (Put the Coasties and marine police into your cell phone!) 300 miles offshore, both are useless.

BTW, because of cable and/or connection problems, my masthead antenna and fixed VHF don't match my handheld... I'll be trying to resolve that before the mast is stepped. In an emergency, I'll bet on the handheld!

Edited by - on

John V.
Admiral

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USA
559 Posts

Response Posted - 01/10/2006 : 00:55:58

I have only sailed on the ocean a few times so I don't know what regulations apply to radios there. I do know that on the Great Lakes, The Coast Guard requires that your VHF radio be on and tuned to channel 16 when ever you are in operation. A mast mount will assure that your call will be heard at the greatest distance. In the case of a Mayday you may be the closest vessel and will have to respond. If you can talk to a distant CG base or vessel you may be able to render aid or relay messages. I have two mounted VHF radios on board, one all weather mounted in the combing box in the cockpit for ship to ship and to call marinas for docking instructions, and one in the cabin as a back up and for calls made during down time. the two radios share the masthead antenna through a coax antenna switch. there is also a handheld in the abandon ship bag. that sits under the companionway steps and can be pulled and thrown in the dinghy in a moment. I keep survival gear in the bag along with a spare handheld gps. In an environment like Lake Superior, there are some wicked deadheads that may be over 20 inches in diameter and as much as 25 feet long. they tend to lurk in the vertical and may remain submerged most of the time making a pop to the surface so briefly as to never be reportable. This is the kind of danger for which you need a good radio system. Especially if you are 25 or more miles off shore.

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djn
Master Marine Consultant

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USA
1561 Posts

Response Posted - 01/10/2006 : 01:22:05

Hi John, were is Neebish Island? I hail from Lake St. Clair. Cheers.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 01/10/2006 : 08:57:55

While keeping the radio on and tuned to channel 16 is a good thing, and I don’t disagree with it, your coast guard requirement above is a bit errant.

According to coast guard and FCC regs, boats that are not required to carry radios – such as our boats only have to monitor channel 16 if the radio they have is on and not being used to communicate. (for example being used for racing).

http://www.navcen.uscg.gov/marcomms/watch.htm

U.S. recreational vessels not required to carry radios
Vessels not required to carry a marine radio (e.g. recreational vessels less than 20m length), but which voluntarily carry a radio, must maintain a watch on channel 16 (156.800 MHz) whenever the radio is operating and not being used to communicate.
Source: FCC 47 CFR 80.310

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/10/2006 : 09:27:43

In addition to what Duane said, the FCC regulates radio usage for recreational vessels not the USCG.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 01/10/2006 : 10:16:14

To add on to don - for vessels our size and or recreational use under 65 feet a license is not required except

If you are going on an international voyage That would include Canada – or sailing in Canadian waters for you great lakes and Lake St. Clair Folks (Redundant only to Al Gore)

Or are a documented vessel – there are a couple of guys who have gotten this done, but I’m not sure how they snuck our boats through.

OR If you use satellite communications – including SAT phones but not including EPIRBS

OR Are using MF/HF Single side-band radio

Or Telegraphy – which I’m sure all of us are using on our 25 foot sailboats….LOL

Lastly, if your VHF has digital selective calling you need to get an mssi (maritime mobile service Identity) and if you know what the heck that means, please post it, because I sure don’t.

Edited by - on

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 01/10/2006 : 10:29:48

OK, let me add my two cents to this conversation.

1. Your ability to recieve distant stations is not a function of the power output of your radio. It is a funciton of the power output of the sending station and height of its antenna.

2. The higher your antenna above the surface, the farther over the horizon your radio will transmit,up to the limits of your power output and atmospheric conditions.

3. The FCC regulates and assigns frequency use within the electromagnetic spectum (am, fm, vhf, uhf, ssb, etc). The Coast Guard polices the users. Therefore, it is illigal to transmit on a vhf marine rardio from shore unless you have the proper permit from the FCC. The Coast Guard can arrest and prosecute you for doing so. The FCC sets the use for channel 16 as a hailing and safety frequency only. The Coast Guard can arrest and prosecute you for it's improper use.

4. In my opinion, everyone should carry a marine vhf radio on their boat for safety reasons. Whether it's a fixed or handheld radio is immaterial unless you are sailing beyond five miles of shore. A wel-maintained fixed mount radio, with good antenna wire connections, and good atmospherics, should be able to transmit up to 25 miles. The added range is important the farther a field you sail. If your life depends upon it, not necessarilly the floatability of your boat, you will want to reach out as far as you can. Finally, the Coast Guard, and evey other search and rescuer, use vhf radio to conduct SAR operations, not cell phones. Besides, how can you expect to reach out to anyone with a .3 watt cell when you can't get beyond 5-10 miles with a 5 watt handheld radio?

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 01/10/2006 : 15:12:09

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by aeckhart
 Besides, how can you expect to reach out to anyone with a .3 watt cell when you can't get beyond 5-10 miles with a 5 watt handheld radio?
<hr height="1" noshade id="quote"></blockquote id="quote">
No argument about carrying a VHF, but there are circumstances where you can be out of range of a Coast Guard receiver, or being "covered" by other boaters' transmissions closer to the CG, but in range of an on-shore cell tower. (Cell phones don't transmit to or receive from each other.) If you can reach any cell tower, you can contact anybody anywhere--CG, police, Starbucks, or whatever. I've used a cell phone to talk between boats when sailing with friends--works better than hailing and trying to find a channel.

Edited by - Dave Bristle on 01/10/2006 15:15:04

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 01/10/2006 : 15:48:17

My 8 foot high gain quarter wave antenna on the stern rail works better than my 3 foot whip on the masthead. However, I still have the masthead antenna wired and can use it in a pinch. I have a 25 watt fixed VHF, and a 5 watt battery powered handheld. I have a connector to hook my handheld up to either fixed antenna in an emergency. Everything on my boat that uses batteries uses AAs and I always carry a big box of those. I also never go sailing without my cell phone.

You would be crazy to sail in the ocean or Great Lakes without similar emergency communications equipment.

Your first "Mayday" should always be on the VHF because they can "DF" your position.

Here in SOuthern CA I believe you can talk to USCG and Vessel Assist or Sea Tow up to about 100 miles offshore on the VHF because they have big, high gain antennas located on inland mountains combined with much higher power transmitters.

Last Sunday when I was listening to the radio it was a private boat talking to the Dana Point Harbor Patrol on the water in Dana Point 65 miles away. Those kinds of things happen because of "skip" off the atmosphere and the sea.

If its rough seas, strong winds, reef kind of weather I always put on my life jacket and the VHF to 16.

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