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Random Quote: Dignity's got nuthin' ta do with it. You're hangin' out with us now! Syd the sloth (Iceage)
I live on the Sea of Cortez in a sparsely populated area of the Baja peninsula in Mexico. It is not unusual to fish for one, or two, or three days offshore and not see another boat. A handful of fishermen maintain base vhf stations in their homes. With a regular 25 watt vhf unit one can usually maintain contact with somebody in another boat or ashore within 25 to 30 miles. I would like to increase that range, if it is practical. I think, but am not sure, that with a 2 meter radio comes an increase in power from 25 watts to 50 + or -, and a commensurate increase in range. My questions are:
1. Is it true that increased range in communicating with a regular marine band vhf radio can be achieved with a 2 meter radio?
2. Does a 2 meter radio require a different antennae than a regular 25 watt vhf marine band radio?
3. Is it possible/practical to mount a 2 meter radio on a center console fishing boat?
4. What unit would be recommended for either a base unit or a boat mounted 2 meter radio that would be used not for any other ham radio purpose but only to increase the range on marine band communication, and not also break the bank?
You are wasting your time, and you money trying to use 2m ham radios to increase range on a boat. I have a ham license, and 2m base station and mobile radios, and I know it isn't going to get you anything. What I would recommend is to improve the antenna's on both base and boat, using the VHF marine radios. A better antenna system will give you far better range that your 2m idea. A beam or other positive (not unity gain, which is zero) gain-type antenna at the base station, and an elevated 9db gain, high quality antenna on the boat will work wonders.
__________________ Capt Will, 2002 G/W 282 Sailfish, F225's
USCG Master, 50 Ton; Towing endorsement
Indian River, De
Will......I presently have a Shakespeare 5225 at my house and a Digital 529 (I think) on the boat. Both 8' antennas. Specifically, what antennas would you recommend? And, are you suggesting that a 2 meter radio at either the base station and/or on the boat would not serve to increase range?
Yes, Bill, there is only about 8 mhz freq difference between VHF marine and 2 meter bands. 2 meter is 144-148 mhz, but you would be using the upper half. VHF marine where is roughly 156.5 +/-, so there is no gains to be had. They are both vhf bands.
But antennas are where great things happen, and hams even using very low power have achieved great distances, with the proper antenna, among other things. If you were to elevate your base ant, and make it directional, even if only to some degree, you will be focusing your power where you want it.
The boat limits your ant choices, but a correctly tuned, low swr, 5/8 wave 9db will improve range quite a bit.
Here's a link to some good stuff that you should know, and this applies to VHF marine.
I'm not a radio geek, but why not either an SSB or sat phone? People around here can go hundreds of miles with ssb, and sat phones are just dependent on satellites in your territory.
It would seem either of those would be better than either trying to get more range from a vhf or using a ham radio. You do need someone on the other end .......
__________________
Terry Jason 35, Yanmar 370 hp, Lots of fun at a leisurely pace
The information on the site you provided is very helpful. It looks like a good place for me to start is to replace the 8' 6db antenna at my house with a 9 or 10 db unit. I found longer 9 and 10 db antennae made by both Digital and Shakespeare, which would have the additional benefit of increasing elevation. You mentioned also directional control. I only need 180 degrees coverage from my base. Is there a way to focus an omnidirectional antenna for such coverage and increase power? Or are antennae available that are adjustable?
As to a 9 db 8' whip for my boat, I checked the Shakespeare and Digital sites and came up dry. Are you aware of a manufacturer that makes an 8' 9 db whip?
Gerg,
It does take two to tango. I agree that a sat. phone is a good idea for emergencies, but here I'm trying just to increase the range on regular vhf communication, both for routine communication from my boat and monitoring routine and possibly emergency calls from home. I fish offshore a lot alone both on the Sea of Cortez and the Pacific and do plan to get a satellite phone some time soon (probably iridium), but that is another thread.
Gotta get this clear. You want to use a 2 meter Amateur radio on the VHF frequencies. Right?
One issue is that would be illegal. It can and is done. That 2 meter radio would have to be "unlocked" to go to the VHF frequencies and that modification could be done. It might not be "tuned" for peak output there but that is also possible. Then you would need to remember to use it "simplex" when on VHF frequencies.
Another issue is your basic premise - to get more power. Well, normal VHF radios are set for 25 watts. Ham radios can put out more but how much more? Even doubling your power will not get you much of an increase in range. Making antenna change to get more db's - either through height or design - has the potential for better results and that would also be legal.
Not sure how Mexico enforces communication laws but doubt that's a real issue for the little use you would have of it. If they caught you it could be nasty unless you are a licensed amateur radio operator.
Lots to think about. My suggestion is to use a good VHF and get the highest, best antenna you can get. Of course you could also just buy a 2 meter amplifier to boost your power.
As to a 9 db 8' whip for my boat, I checked the Shakespeare and Digital sites and came up dry. Are you aware of a manufacturer that makes an 8' 9 db whip?
Antennas do not have actual "gain", the radiated power is the same as the input power. The "gain" claimed is accomplished by focusing the radiated power in a more horizontal plane. That is, more power is radiated along the earth's or water's surface and less towards the sun and moon.
This focusing is directly related to the length of the antenna. A 4' antenna will have about 3db of "gain", an 8' antenna will have about 6db of "gain" and a longer (I forget the exact length but you can look it up) antenna will have 9 or 10db of "gain".
Going back to the focusing of the radiated power in a horizontal plane, if you focus it too tightly, when the boat pitches and rolls, the radiated signal will no longer be horizontal. Most experts recommend an 8', 6db antenna for a typical power boat and a 4', 3db antenna for a sailboat because of heeling, pitching, etc.
So - put the 10db antenna as high as possible on your house, even on a tower, and put an 8' antenna on the boat.
All of the above is assuming this is legal in Mexico. It is not legal in the USA.
.............. Of course you could also just buy a 2 meter amplifier to boost your power.
You can boost the base station to a million watts if you want, but if the station at the other end is only 25 watts, you won't improve two way communications one bit.
Bill, you will need to go to a 17'6" antenna for 9db. Not sure what kind of boat you have, but you can probably set up one of these with a lay-down mount, on just about any boat.
For a base station, a vertical is omni-directional. You will need to make (or buy) a yagi, for concentrating transmitter power to a general direction. The more elements, higher-Q, the more gain and more directional the yagi becomes. So either just put a 9db gain marine antenna up, at the best elevation you can, or build a yagi with only 2 or 3 elements. It can be made of copper wire, and bamboo poles or pvc pipe.
This approach will yield much better results that doubling or tripling transmitter power, because you can't qso if you can't hear the other guy. Improving antenna performance will concentrate transmitter power where you want it, and will increase receiver performance by feeding the receiver with a stronger signal. All this, and legal, too.
I've built a lot of antennas over the years, and this would be a fun project. Too bad we're not closer.
__________________ Capt Will, 2002 G/W 282 Sailfish, F225's
USCG Master, 50 Ton; Towing endorsement
Indian River, De
10%.......I don't know what exactly it is that you are asking to be clarified. Will seems to have understood my questions and responded very helpfully. As to your assertion that it would "be illegal", Mexico does not enforce US law. I'm not sure what Mexican law is on the matter, but I did not ask that question and would not come to this forum to find that out. If you know how I might accomplish what I want to accomplish by adding an amplifier on my boat / base unit, I would like to hear about it. I think that I understand my options with antennae (with the exception of the directional issue on the base unit) from the information Will provided.
MORAD makes a shippable 10dB antenna that would likely work on your boat and shore station; they aren't cheap, but they'll probably outlast you and your boat.
Will......Maybe you should just fly down here to assist on this project. I could probably send you back home with a cooler full of fresh wahoo and yellowfin fillets. Attached is a photo of my palapa where my base unit is installed. The 8' 6db antenna I am presently using is visible sticking through the palm frond roof. I can easily replace it with a longer 9 or 10 db unit and support it up 3' or 4' as required. I could not mount the longer 9 db antenna on my boat. I can, and will, shorten the coiled coax in the center console as much as possible to reduce loss of gain, as per the materials you referenced, make sure the connection is good, and live with what I get on the boat from my Icom and 8' Digital 6db. As to the base unit, I will get a longer 9 or 10 db antenna, make sure it has a proper ground plane, make sure it is wired with low loss RG-8X coax, and live with the result, which will probably be a noticeable increase in my present range. Unless, that is, I figure out what a yagi is and decide to either buy or attempt to make one, or you decide to come down and assist on the project. Thanks for your help. And thank you, too, rwidman for the information on focusing the radiated power in the horizontal plane with an antenna mounted on the boat. I had pretty much gleaned that from the materials Will forwarded, so am not too disappointed about not being able to mount a longer 9db unit on the boat.
Bill, wow, thanks for the invite. Almost tempted, but let's try something out; an idea or 2. I'm going to provide you with a few more links; a calculator, (there are many ways and even just use the simple formula for determining antenna element length), and a link on how to homebrew an antenna for cheap, out in the boondocks. The design came about from a couple of hams in Cuba. As you would imagine, it would be tough to find parts to build an antenna there. This is the result of some ham ingenuity, and the 144 mhz antenna dimensions can be scaled down slightly, (use the calculator, or ant. formula), and it will work perfectly on marine VHF.It can be vertically polarized, for best communications with a boat, and is fairly inconspicuous. There are many other design approaches, and the ARRL Antenna Handbook is a valuable resourse, and easy to understand:
Antenna element length calculator.
Enter a marine VHF freq, such as 156.5, to see the element and antenna dimensions: http://bfn.org/~bn589/antenna.html
Nothing substitutes for height. A 25 foot high antenna at the Palapa, and 12 foot high antenna on the boat will give a "line of site" range of about 12 miles. If you increase the Palapa antenna to 50 feet, you will get 15 miles. By higher gain antennas, you will push the signal out a few more miles, and same with the amp.
Forget about 2 meter amps--there are a number of reasons not to use them, but best is that there are specific amps made for the Land Mobile and VHF Marine specturm in the 156 to 157 Mhz ranges. These are available up to 200 watts.
Even though I have spent several years cruising Mexicio and had Mexican Ham reciprocity, I have no idea of the legal aspect of using 200 watts on Marine VHF from a land station. My suspician is that the stronger signal and higher antenna, would raise some inquiry, but maybe not....
The reality is that physics basically limit your range, unless you have trophespheric ducting--and that can give extended ranges, that are un-reliable.
Will......."and the ARRL Antenna Handbook is a valuable resourse, and easy to understand" That is easy for you to say. The extent of my electronics expertise ends at the point where I turn on my Icom and adjust the squelch. One of the reasons I live on Baja and not in Cuba is so that I don't have to make my own antennae. It is interesting that Kent was in contact with the Cuban ham and designed an antenna that could be made from things found around the back yard. My inclination, however, is to try to find out from knowledgeable people like you what I might buy to best serve my purposes, and then get it, install it and go fishing. I think I know now what to do to increase the range on my base unit, if not the radio on the boat. Maybe with more power I will be able to receive a call sometime from somebody broken down far offshore and in need of assistance. I've been on both ends of such calls a couple of times. There are no private services or coast guard to respond to calls for assistance down here, so concern about compliance with rules that may or may not exist is not really a part of the discussion. Thanks again for your help.
thataway.......Do you think that keeping the 8' 6db whip antenna that I presently have on my boat and adding a vhf marine amplifier to boost the watts to 200, or some other number greater than 25, would significantly increase the range on my radio?
Get a SSB radio and ant. at both sites. Tuned properly, they can talk al over the planet.
That has been mentioned is a previous post, but Bill wants to stay on VHF so others can hear/be heard, if help is needed. So I think he's trying to extend VHF range, so other boaters with existing vhf also have a better reach.
__________________ Capt Will, 2002 G/W 282 Sailfish, F225's
USCG Master, 50 Ton; Towing endorsement
Indian River, De
2 Meter Radios? 
