The range of VHF radios

[btrayfors]

There are several ways to skin the VHF cat in the cockpit!

Remote mics, antenna switches, 2nd radio....all work, though there are some caveats to each. Here are a few negatives for each option:

1. Remote mics. Not all VHF radios are set up to take them. Those that are generally have high-priced remote mics ($100 or more)...almost the cost of a second radio. Remote mics in the cockpit can be easily stolen. Remote mics often suffer from exposure, especially the rubber and the connectors, giving them shorter life than you'd expect from such an expensive piece of gear. I know....I have one on my Standard Horizon VHF. And, I'm paranoid enough to remove it whenever I leave the boat and stow it below.

2. Antenna switches. I'm not in favor of this option because if you forget to turn the switch you might not have the radio you're using connected to an antenna, thereby rendering it useless and, perhaps, doing damage to the radio. And, connecting to an antenna atop the mast isn't always necessary (see below).

3. Second VHF in the cockpit. I like this option, but it is a bit more expensive than Option #1. It also requires the purchase and installation of a 2nd antenna, to mount on the pushpit or elsewhere. However, given the very low price of decent basic VHF sets these days, this is a pretty good option IMHO.

Most, though not all, VHF communications from the cockpit involve short-range contacts (with other vessels in sight, with dingies, with bridges, shore facilities, etc.). These can easily be made with either a handheld or a second VHF with an antenna on the stern somewhere. The advantages of the 2nd set vs. the handheld are: (1) more power; and (2) no need to worry about charging the batteries.

Another "advantage" of a handheld or a 2nd VHF is that you won't have to listen to a lot of VHF traffic from far away which really doesn't concern you anyway :-) Sometimes my remote mic in the cockpit -- which is connected to the main VHF below and, in turn, to the VHF antenna atop my 64' mast -- drives me crazy when I'm trying to relax in the cockpit, and am picking up VHF stations from many miles away....including the very powerful Coast Guard Stations as much as 150 miles away sometimes.

Bill

[Therapy]

Originally Posted by btrayfors

Most, though not all, VHF communications from the cockpit involve short-range contacts (with other vessels in sight, with dingies, with bridges, shore facilities, etc.). These can easily be made with either a handheld or a second VHF with an antenna on the stern somewhere. The advantages of the 2nd set vs. the handheld are: (1) more power; and (2) no need to worry about charging the batteries.

Another "advantage" of a handheld or a 2nd VHF is that you won't have to listen to a lot of VHF traffic from far away which really doesn't concern you anyway :-) Sometimes my remote mic in the cockpit -- which is connected to the main VHF below and, in turn, to the VHF antenna atop my 64' mast -- drives me crazy when I'm trying to relax in the cockpit, and am picking up VHF stations from many miles away....including the very powerful Coast Guard Stations as much as 150 miles away sometimes.

Bill

I think you have it nailed.

[David M]

Actually there is some bending of VHF transmissions around hills and mountains and a little over the horizon. Its not absolutely line of sight. I experience this frequently working on the SF Bay. 156MHz does bend some, unlike frequencies over 1GHz which truly are line of sight.

I aways pack any exterior electrical connections with silicon grease. Silicon grease does not affect petroleum based seals.

[RBEmerson]

Amen and "what he said".

[bene505]

I'd go for the totally separate VHF radio with an antenna on the pushpit. Full redundency means that if any one thing breaks, you have a second system that works. It's also simpler to use than an antenna switch, as Btryfors pointed out. When the crap hits the fan, simpler is better.

To me, a handheld (with spare batteries) qualifies as a totally separate system. And if you ever have to step up into a liferaft or dinghy, you can take it with you. And if you are crewing for a friend, you can bring it with you then too.

[RBEmerson]

Bingo! Even though we know have a second mic in the cockpit (Icom M604), I still keep a charge on the handheld, too. Ya never know when...

[Talbot]

I recently bought two new vhf antennas, and cables.

The expensive one had normal copper cable. The cheap one had tinned cable. The cheap one was half the price of the expensive one and had twice the range!

JGtech 1m stainless whip has my vote. (for UK members)

[nautical62]

Originally Posted by btrayfors

...Another "advantage" of a handheld or a 2nd VHF is that you won't have to listen to a lot of VHF traffic from far away which really doesn't concern you anyway :-)
Bill

That's a very good point Bill. I'm often find I wish to fulfill my desire to monitor the VHF but go crazy when I'm in a secluded area listening to all the chatter miles away that has nothing to do with me.

[hellosailor]

Talbot, for marine use, tinned cable is pretty much madatory. But coax cable can also be very different from one make to another, some use a 40% shield while others use a 100% shield--which requires 250% more copper and commands a much higher price. And performance. The other differences are even harder to tell unless you can find and read the specs on it.

[btrayfors]

Yes, there are many, many types of coax cable. It can get very confusing, trying to sort them out. Here's just a sampling of what's available in the coax dept.: http://therfc.com/coax.htm

Is this really important? For VHF use on a sailboat, yes, it is. This is because the run from the radio to the top of the mast is often a longish one, and power losses can be severe.

Take, for example, the commonly found RG8X or "Mini-8" coax. At VHF frequencies used for marine communications, the loss in this cable is 3.8db per 100'. That's a loss of more than half power, like cutting your radio output power back from 25 watts to 10 watts or less.

The larger diameter coax cables (0.405") are less lossy, and these come in several varieties. RG-8 is common, but RG-213 and RG-214 are even better.

I like RG214Comm because it has double 98% tinned copper braid which helps to reduce RFI and it has an AWG10 tinned stranded copper center conductor. It's attenuation per 100' @ 150mHz is about 2.3db. It's also pretty rugged stuff and likely to survive the rigors of life aboard even the saltiest seagoing vessel.

Bill

[RBEmerson]

Originally Posted by nautical62

That's a very good point Bill. I'm often find I wish to fulfill my desire to monitor the VHF but go crazy when I'm in a secluded area listening to all the chatter miles away that has nothing to do with me.

Heh, heh, heh... one of the nice things about the M604 (and other radios towards that price range) is the built-in attenuator, which dampens down signals. Now add a "stupid" filter to weed out the really vapid transmissions (and, gee, let's add a gizmo that shocks the socks off any fool leaving the mic keyed up!), you'd really have something.

[H/V Vega]

When I was flying we learned that the distance for a VHF was calculated by the root of the height of the antenna times 1.23 + the same applied to height of the other guys antenna. It is pretty close. By the way watch out with power ratings. These days it seems there are several ways of measuring watts. And not all 25 watt radios actually put out a real useable 25 watts. I have seen 25 watters that were hard pressed to get to 10 watts on a calibrated output meter. Seems that anything goes if it convinces you to buy it.

[nautical62]

To get at a couple other points in your original post:

1. With a mast top antenna, I can usually still pick up NOAA weather radio and the coast guard at the near islands such as West End or Bimini, but not other boats in the Florida area. By the time I move any farther east, I can't even pick this up. For reasons described above, your results may vary a bit from this. In the Abacos, I can usually pick up the cruiser's net in Marsh Harbour somewhere between Powell and Green Turtle.

2: Mounting Location: After having VHF radios mounted in several locations, above the nav. station is my least favorite. Unlike a large vessel, I find in a small boat, nobody man's a nav station in a small sailing vessel. Unless I have a remote mic, I can't hear it, make any adjustments or talk on it from the cockpit, which is where I'm often needed at times I want to use the VHF. The solution I've liked the best is to have it on a swinging mount just inside the companionway , so it can face in and be easily used from inside or swung out so it can be heard and accessed from the cockpit.

One can of course use a handheld in the cockpit, but then you are back to the disadvantages you already know about. I've had several times where marinas and bridge tenders won't answer me on the lower power of a hand held even though I'm close, that included one very frustrating experience trying to communicate with a marina in Nassau when solo dealing with a current and for what ever reasons they could barely hear me from less than half a mile.

I always want to have a base station accessible from the cockpit either by itself of via a remote mic. (Knowing me, I'd loose the remote mic.)

[s/v Jedi]

Ah, RF at vhf freqs, my original profession ;-) Some points:

- Your radio is supposed to have 50 nm range between you and shorestations and other ships. Sailboats achieve that by putting the antenna (3dB gain) on the masthead, motorboats use hi-gain stacked dipoles 8' long or more.
(beyond 50 nm the required radio is MF, ie. 2182 kHz). These are the GMDSS requirements as implemented by coastguards/SAR services worldwide.

- Replace the antenna, it's to cheap to take chances. A dipole is better than the stainless whip (= base loaded groundplane but lacking the ground plane) Shakespear has a 3-foot dipole in black & white (black lasts longer in the tropics). This antenna is more difficult to install as it needs a mount on top of the mast instead of against the side and it doesn't have a connector for the cable but instead a length of cable permanently attached. You need to shorten that (thin) cable to minimum length and solder a connector on. Use a female-female adapter to connect the antenna cable and use adhesive walled heat shrink.

- coax cable ages and needs to be replaced like every 5 years. I don't think anyone does so but you really should replace it after 10 years ;-) Use RG8U tinned minimum (ancor is good quality) (motorboats can use RG8X as the length of the cable is much less). RG213U is better but doesn't last longer and more expensive... RG8U is good enough.

- select a handheld with detachable antenna that uses BNC plug/connector. Now buy an adapter so you can connect you ship antenna to the handheld (very cheap). This increases handheld range enormously when main radio breaks. Range will be almost as good as with mounted radio.

- test the system using dummyload and swr meter (or antenna analyser). Install the dummyload at masthead instead of antenna too before putting heatshrink on.

cheers,
Nick.

[hellosailor]

Vega, part of the reason that all 25-watt radios are not created equal is simply quality control. Electronic parts vary in quality and performance, designs vary, and these days electronic manufacturers use accountants to tear apart the final design--sometimes after certification--to see what components can be removed to reduce the production expenses.

If you buy a top-name radio (SSB or similar, VHFs are simply too cheap to invest time in) the odds are that it was checked and tuned at the factory for maximum legal output. Buy a commodity-grade radio, or cheaper products like a VHF, and it has just been assembled--not tested or tuned. And their goal is not to exceed the legal limit, so no one really cares if 25 watts is 18 or 22 on a given radio, as long as it is not 25.1 and as long as nothing is overloaded causing a warranty expense. And of course in order to ensure the random variance in parts doesn't exceed the rating--you have to shoot for something below it.

A radio tech can easily tweak your radio, but with tech labor at $75-125 per hour that can double the cost of your radio. Who's willing to ante up?

There are big savings, and gains (pun intended) to be had by getting a book on antennas, something practical and hands-on like oriented for ham radio ops, and then setting up your antenna with no voodoo, just simple physics and knowing the right choices to make, instead of gambling on the salesman.