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VHF range

2648 Views 21 Replies 11 Participants Last post by  Spider
I'm still pretty green at marine electronics. Although I sell industrial electronics I have no clue once it comes to the boat side of things.

My VHF seems to have a pretty weak signal. I have problems getting in touch with most anyone on a clear day. It's not in the water yet so I haven't tested it this year, but last year I tried a radio check from our marina quite a few times and never got a response back. It did work with some folks that were close to me at another location, though.

My question is, does where you're at (ie a marina, out in the middle of the lake, etc) affect your signal? I can receive/hear just fine and I usually can hear some distance away (Old Club, while at 11 Mile & Jefferson). Is it an antennae problem? My radio looks in fairly good shape (the boat's 7 years old). My antennae pole jiggles around in the base, where it looks like it was at one time caulked or filled with epoxy of some sort. Could this make a difference? I thought the pole was only a means of getting the wires up higher above the boat.
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Absolutely not. There are different db gain antenna's on the market. A good one costs about $100. but its worth every penny. When I was at Schmid in new baltimore I could talk to a friend at Radlins on the Thames river as clear as if he was next to me. Thats about as far as you can get on LSC. Also the solder job on the radio connector willl have an effect.
VHF is line of sight from the tip of your antenna. The higher up it is, the farther you'll reach. And hammers right, good antennas cost 100$ or more. The more the gain in (db) the better. Boat antennas are actually 2 antennas: one to receive and one to transmit. Sounds like you can receive fine, but lack transmission distance. Definitely try a new antenna.
I have a some problem., but my VHF looks kind of old. I may tray buy a new one and later check the antenna?
Does anyone know what range u can get out of a handheld VHF? I ride a watercraft and was thinking of buying a handheld VHF radio just in case, but since I dont know the range, I dont want to waste my money. Has anyone had any luck with these?
As noted, VHF is line-of-sight, so the limiting factor for range is typically the curvature of the earth. The usual usable range for a console unit with an 6 or 8 foot antenna is maybe 15-25 miles. The Coasties mount their antennas way up on towers, so they get better range.

Second, the broadcast power of a recreational VHF is not exactly overpowering. When you're looking at a handheld, it has both a shorter antenna and much less power, so range is severely limited. I'd only use one as a backup to my regular VHF.

That being said, any VHF is better than no VHF.
In handhelds the output watts vary. Go for a higher output model and you should be fine. I always carry one on the dinghy and its good for at least a few miles.
Thanks for the info. Convincor's gonna help me test the thing out, though if it's line-of-sight, we may have trouble doing it on land. We talked about the solder connection at the base of the unit so I'll check that out first.

Shakespeare's got a gaget that you can hook between your radio & antenna. It will tell you what if anything is wrong. It will also tell you how many watts youre putting out. I had the same propblem last year. I found out that my antenna was a cheap one & that the windings only went about 1/4 the way up. The rest of the fiberglass was just for show.. Get a Galaxy 5225 I bout one & can talk about 20 miles.
SMOOTH is right, its sometimes called a field strength meter, or standing wave ratio (SWR) meter. RadioShack has on for about 12 bucks or, like SMOOTH said:

for info on the Shakespeare unit.

Also, the url takes you to West Marines e-catalog. if you scroll down to the bottom of the page, you'll see that you're on page 70. Hit the previous button until you get to page 65 and you'll find a good explanation of how a VHF radio works.
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Sorry, I screwed up! that url takes you to the e-catalog. You gotta type in the page number at the top (70 for the meter, 65 for the VHF info)
As well as a Boater2Be I am an amateur radio operator. Marine VHF is very similar to the 2 meter Ham band. Both are FM and they are only a few MHz apart in the radio spectrum.

One of the most common problems is with the connector on the end of the coax (antenna cable) that connects to the back of the radio. In a rough and wet marine environment it is common for that connecter to come loose or get corroded.

Also check the routing of your coax. Make sure that it is not pinched, bent at a sharp angle or cut. The first two conditions can cause a short in the coax. I don't think that is your problem or your receive would be suffering too. A cut will allow moisture in and the cable it will corrode. This could cause a bad shielding condition letting RF (radio frequency energy) leak from the coax before it gets to the antenna. Also if your coax is too long and the installer coiled the excess that can create an electronic choke that can hamper your performance. Cut it to the required length an install a new PL-259 connector (at the radio end of the coax). Properly soldering one of these connectors can be a royal pain! If you can find somebody that has experience in this and has the tools, buy him or her a case of beer and bribe them with a day on the water. IT will be worth it. There are solder-less PL-259 connectors but I don't recommend them, even in a calm, dry environment. You get a much better connection with solder.

If improperly done?

1. Too much heat will melt the insulator in the coax that is between the center antenna lead and the outer RF shielding causing a dead short.

2. Improperly strip and prep the coax and you will have a dead short or will not be able to make a good connection.

3. Not enough heat and the connection wont hold for long if at all.

A dead short is the worst case because if you continue to try to transmit with that condition you will damage your radio.

If you find that you need to replace your antenna. Remember, your mounted radio is 25 watt max output (FCC law). So like Hammer said use the highest gain antenna you can afford and fit on your boat and mount it as high as possible. Also use the shortest amount of coax possible for the job. (It's tough to do both, but a good balance of height and coax length will get you the best results. VHF signals will "leak" slightly through the shielding of the coax causing some signal loss at the antenna. (Yes even brand new perfect condition coax.) The longer the coax the more db loss you will have.

The only thing in the previous posts that I disagree with was the statement that, "a marine antenna is actually two antennas. One for receive and one for transmit." This would only make sense if the transmit and receive frequencies where drastically different. This is not the case with marine VHF.

As for the hand held question. Most hand held marine radios are 5 or 6 watts max due to battery and size limitations. On land a hand held 2 meter ham with 5 watts and the typical "rubber duck" antenna will get you 2 to 5 miles of clear communication depending on terrain. As stated before, line of site is the limiting factor for VHF. Take the same hand held to 1500 feet in my friend's hot air balloon and I can talk for 100s of miles.

As mentioned on the water the curvature of the earth limits your line of site. If you can find a quite channel, (good luck on LSC) you should have useful range of 3 to 7 miles depending on atmospheric conditions. If the rude few that don't know or care about marine radio manors have a stronger signal, and they continue to talk over you. You will lose.

One of the other drawbacks to handheld radios is poor noise rejection. In other words it will pick up more noise from a conversation on a neighboring channel then the larger fix mounted radios will. Sometimes even cell phones and pager antennas near the city will cause interference. This may prevent you from hearing the party you are trying to talk to.

All of this said if I where buzzing LSC on a PWC I would have one with me. In an emergency even if you can't contact help on land, another boater may hear you and be able to relay the message. Also I believe coastguard choppers monitor the marine band emergency channel listening for maydays. With there altitude your range would be extended.

I would look for one with a good waterproof rating, one that floats. Make sure that you keep the batteries charged or get one that will run on both rechargeable and alkaline batteries and carry spare batteries.

Good luck guys I hope all of this babble helps.
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Boater2Be, you should be Boater4Sure!

Thanks for the info. I'm going to inspect the coax and the solder connection at the radio end. I know my antennae is a Shakespear, but that's about all I know without getting into it further. I try some of everyone's suggestions and report back what i find out.

Thanks everyone for the help!
QUOTE(damn yankee @ May 29 2003, 04:58 PM)SMOOTH is right, its sometimes called a field strength meter, or standing wave ratio (SWR) meter. RadioShack has on for about 12 bucks or, like SMOOTH said:

for info on the Shakespeare unit.

Also, the url takes you to West Marines e-catalog. if you scroll down to the bottom of the page, you'll see that you're on page 70. Hit the previous button until you get to page 65 and you'll find a good explanation of how a VHF radio works.

West Marine has a special for Shakespeare units .
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I have a Shakespeare 8' for sale in the Boats& Accessories forum.
Ever since this post started I've been paying attention to the range boats in our club can get. It seems they can hear me but I can't hear them. Height and quality definately make a difference.
Hammer, I wonder why they can hear you so well? You have allot of practice screaming when buying rounds of shots!

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Attention channel 69, shots at Metroooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
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I'd like to offer a few suggestions on the subject of this thread as an FCC licensed professional with 35 years of experience in the business...

It has been mentioned earlier in the thread- a good antenna properly installed makes a huge difference. Gain is also important, but remember that in an antenna, as the gain is increased in one portion of the sphere of radiation, signals are decreased in others. High-gain marine antennas radiate in an omni-directional pattern with a very narrow vertical lobe close to the horizon. This means that if your boat pitches and rolls significantly, that area of radiation (and reception) will be moved away from the horizon causing signal flutter and fading. Lower gain antennas with broader radiation (and reception) lobes will minimize this phenomonon. They key is to use the highest gain antenna that your platform will support, and get it as high as is practical.

I can't agree strongly enough with the discussion regarding connectors and connector installation. In my years of checking, most of the connectors installed by users just weren't installed properly. Installation of these connectors looks simple enough, but it isn't. There are a lot of things that can be gotchas to someone inexperienced with the procedure. If you don't do it right, you won't have a reliable radio system. If you are going to try to do the connector job yourself, find an expert to show you the proper way to install the connector. If you don't feel comfortable installing it yourself, have it installed by a professional. Whatever you do, avoid crimp-on or screw-on connectors like the plague. They are unreliable junk.

Once that connector has been installed, it must be verified. A good thru-line power meter can be a help here. Good ones are very expensive. The accuracy of a power meter is rated at the range's full scale value. That means that trying to make accurate readings at the bottom of a scale is problematic. A decent wattmeter will have removeable slugs that allow the range to be changed for taking forward and reflected power readings. Once that connector is installed, verify that the forward and reflected power is within acceptable limits. Most radio shops use high-quality power meters to make these checks. I prefer an additional check with a time-domain reflectometer. This instrument uses traveling pulses to analyze the entire connector/feedline/antenna system. Defects in connector installation, coaxial cable anomalies, and antenna issues can be readily discovered. They are very expensive, but the wealth of information made available is priceless.

And to re-iterate a previous post, there are not separate antenna elements for reception and transmission. A marine VHF antenna is a single radiator in a weatherproof radome.

Coiling coaxial cable does not produce a "choke effect" to the radio frequency energy traveling inside the cable. Coils of coax are invisible to the RF traveling down the cable. Because of the skin-effect, high frequency radio frequency energy travels only on the surface of a conductor. A coaxial cable actually has three distinct surfaces. The outer surface of the center conductor, the inner surface of the shield, and the outer surface of the shield. Improper connector installation and cable defects can compromise this inner-to-outer shield isolation and adversely affect radio system performance. A coiled cable will have "choke effects" on currents flowing on the outer surface of the shield. This is not harmful and is actually beneficial.

Losses because of excessive coaxial cable length do occur, and while cable runs should be designed to be as short as possible, don't get too obsessive about the cable lengths on a boat. An extra few feet of cable isn't going to make a noticable difference. An extra 30 feet of cable will. Always make sure to allow some excess cable in the area of the radio to allow for future connector replacement. Don't cut it to the exact length. If you have a connector fail later or get a slightly different radio, you'll be in trouble.

Finally, let's not forget the radio itself. Is it really making rated power? And just as importantly, is it operating on frequency, or has it drifted a bit? Is the modulation deviation correct, or is it low making you hard to hear or high causing distortion? Is the receiver sensitivity within specifications? If you run into a situation where you can either hear well and can't transmit, or can transmit well and can't hear, you most likely have a radio issue. Get it checked. These checks require a communications service analyzer. If you've decided to get a new radio, have it checked too, prior to installation. A few are bad right out of the box.

And lastly, check the 12 volt power at the connector on the radio. Make sure that under full-power transmit there isn't an excessive voltage sag. Excessive voltage drop in the power cable can cause all sorts of strange radio behavior. Make sure it's within specification.

You might have to depend on your radio to save your life or the life of a fellow boater someday. Try to keep that in mind as you work on your radio installation.

If you've got any questions or need any free advice, let me know.

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Rick. Great post. Thanks! As an amateur radio operator, I appreciate the corrections and conformations. Any time I can learn something form somebody with your experience, I am all ears.
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