Communications Offshore

The following material on communication has been taken from a 2006 update to the Pacific Cup Handbook by Jim and Sue Corenman; editorial comments by Steve Chamberlin.


A VHF radio is required, with a masthead antenna. As mentioned in the Handbook, the size/quality of coax from radio to antenna is critical, and the Special Regs now includes some specific guidance. The bottom line is that most boats over 30’ or so cannot get by with skinny (¼”) RG-8x and will need to use a ½” coax cable to avoid excessive loss. Our recommendation is Belden 9913F or LMR-400, they are lighter in weight than the more common RG-8 or RG-213. And make sure the connectors are sealed against water intrusion.

If you are contemplating a new VHF then get a DSC model (Digital Selective Calling). The advantage is that they have a red “distress” button on the front, and can send a coded distress signal identifying your vessel. And, if you have interfaced the GPS via a NMEA connection, your lat-lon will be included in the distress message. Very important: You need a radio license with an “MMSI” marine-ID number, request this as part of your FCC radio license from the FCC. The Coast Guard is not yet monitoring DSC (it is expected soon) but every other boat with a DSC radio will copy your distress message and can respond directly or relay the info.

Technically, boats under 65’ which are not intending to travel to foreign countries do not need a FCC license. However the MMSI number is tied to your FCC radio license, and you also need a license for the SSB radio. Unlicensed boats can get an unofficial MMSI from Boat-US, this is NOT a good idea because that number will not be listed in the international databases and may not be readily accessible to the various Rescue Coordination Centers (RCC’s). So if you have a DSC radio (or a SSB) you should absolutely get a proper radio license and request an MMSI with it.

A SSB radio is required for most offshore races, and is highly recommended for anyone heading beyond VHF range (25-50 miles). Besides providing communications for roll-call and being an important safety tool, it is also quite handy just to chat with your friends while out sailing. Don’t have friends? You will, the sailing community is a great place to meet folks and SSB radio is how you stay in touch.

Our recommendation for a SSB radio is the Icom M802, it is a good solid 150W radio equipped with DSC (Digital Selective Calling). It also has a remote control head, allowing the radio-box itself to be mounted out of the way (in a dry space with reasonable ventilation- NOT the engine box). One part about the M802 that we do not care for is the small, fragile connector used for the tuner control cable. Make sure it is installed so that the cable is properly secured so the connector is protected from strain.

The issue with DSC is the same as above for a VHF-- it allows you to send a coded distress message if you are in trouble. Again, an interface to the GPS is required in order to include your current position with the distress message. Also, a second receiving antenna must be fitted so that the radio can receive DSC calls. (This can be a small Metz 54” weatherfax antenna mounted to a rail).

Why use DSC to send a distress message instead of calling the Coast Guard on a working channel, or simply turning on the 406 MHz EPIRB? Two reasons: First is that there are different levels of “emergency”. If you have a situation which you believe you can control, but which has the potential to turn into a “mayday” situation (lives at immediate risk) then calling the Coast Guard or other authorities on the SSB (or via sat-phone) is appropriate-- you can establish a two-way communication, let them know the nature of the problem, and set up a watch schedule for future communications. And you can hopefully avoid the problem where a situation escalates out of control when the authorities are brought into the picture. And if it is a serious problem then you need to push all available buttons- EPIRB, DSC distress call, SSB voice, red flares, hollering “mayday” on the ham nets, waving your arms-- in other words, call for help by all means available. And the more means you have, the greater the likelihood that you will get the help that you need.

SSB Installation:

Radio signals haven’t changed, and we still recommend not cutting corners with installation of a ground system/counterpoise. There are lots of ways to do it, and everyone you talk to will give you a different answer. Most of those folks won’t be there when you are mid-ocean trying to make a radio contact, so this is a good time to be conservative and stick with what you know works. Technically the ground-system doesn’t need to be grounded to the ocean, and a “counterpoise” is simply a bunch of metal connected to the tuner’s ground-lug. Copper foil or screening inside the hull works great especially at higher frequencies, also wire lifelines, a stainless “roll bar” and wire of various lengths (called “radials”) strung though the bilges all work fine. The other approach is a direct connection to the ocean, e.g. a copper strap to a metal keel, multiple bronze through-hulls, large Dynapates (except for the drag issue), etc. The key is large area, short connections. Note that we are talking about the ground to the tuner, not the radio— that’s where the antenna ground starts. Other than a potential safety argument in the event of some other problem (e.g. broken coax shield) there is no reason to ground the radio- it is already grounded through the coax to the tuner, to ground.


Radio Interference: One issue that is of growing concern is radio receiver interference from other on-board electrical equipment. This can often be bad enough to render the radio useless, and must be checked for. The worst offenders are shore-power battery chargers, especially the solid-state automatic chargers. These generate interference that can radiate up and down the dock via the power wires, so checking a radio in a marina is pretty hopeless. Get out sailing, anchor in some quiet cove, and check the radio there. Other offenders are some types of AC inverters, especially the small “Statpower” or “Portawatz” units often used to power computers. (Get an airline or auto/air 12V adaptor instead, sold as an accessory by most computer companies). Other culprits are Adler/Barber and Frigiboat 12V refrigeration compressors, some types of 12v florescent lighting, some instrument systems, etc.

The way to isolate this stuff is to anchor in some quiet cove away from power lines, turn off all of the electrical circuits except the radio, and find some weak-but-clear station in the 4-10 mhz range- perhaps WWV on 5 or 10 MHz, or a shortwave broadcast station. Listen carefully as you turn circuits back on, one at a time. If the radio station disappears under static, or you hear squeals or chirps, then you have found a noise source- turn it off and keep looking, there may be more than one.

If you find a source of noise—especially in a new piece of gear-- then start by contacting the dealer or manufacturer and see if they will fix it, or offer a filter kit. If that doesn’t work then a skilled radio technician may be able to help. Depending on the gear, sometimes you can just turn it off. Unfortunately, if it is boat gear, there is no help from the FCC. Every piece of electronics intended for household use, no matter how cheaply made, must meet FCC Part-15 Class-B rules for spurious radio emissions, to make sure that the ball-game on the AM radio isn’t interfered with. But boats, which often depend on SSB radio for weather and safety, do not get similar protection. That’s why laptop computers are (almost) never a problem, but some very expensive marine refrigeration systems can cause serious interference. Our view is that if those folks want to sell into the marine market then they need to respect the fact that offshore sailors use SSB radios for some rather important purposes. And it is up to us to make sure that they get the message.


Telephone calls: SSB radios are great, but since KMI (AT&T High Seas Radio) went off the air it is not simple to make a radio-telephone call via SSB radio. WLO radio still offers radio-telephone service from Alabama, and also from their station KLB in Seattle—see www.wloradio.comfor more info. However if making phone calls and talking to answering machines or voicemail is important to you, then a sat-phone is a much better option- see below. 


Radio email:With the addition of a special radio-modem (and a computer of course) you can send and receive email via your SSB radio. The two primary choices are the Winlink system for hams, and Sailmail for anyone. The two systems use the same equipment and software at your end, but are completely separate shore systems. Winlink requires a ham license of course, and you can find more info starting at Sailmail is operated by the Sailmail Association, a non-profit association which provides email service to its membership. It costs $250 per year to join, and info is available from


A few caveats regarding the use of radio email for the race: Just like yakking into the microphone, radio performance is highly dependent on a good installation and low noise level (see above) and a lousy installation will not work well for either voice or email. And radio email is slow, and connection-time is limited to allow everyone to access the system-- so you may not be able to send/receive as much email as you would like. The alternative is a sat-phone, you can access your Sailmail account via an Iridium data connection and with all the same efficiency and compression as used via the radio link- there is no need to subscribe to another email gateway service.


Sat-Phones:Two companies offer hand-held satellite telephones: Globalstar and Iridium. Both use Low-Earth Orbit (LEO) satellites, but Globalstar is a single-hop (“bent pipe”) system which only works a few hundred miles offshore. That is useless for our needs.


The Iridium system uses satellite-to-satellite relays to provide global coverage for voice and data. That system is both its strength and weakness. The satellites are all in polar orbits, close together at the poles and far apart at the equator. For a connection there has to be a continuous string of satellites from your location to the earth station in Arizona. If a satellite moves on, and there is no satellite with an available channel to take its place, then the string is broken and the call gets dropped. But as long as there are enough satellites relative to the traffic at the moment then it works pretty well- the other limitations being that voices are a bit tinny and data is a relatively slow 2400 baud (with a data-kit). (ed. There are two external antenna options for the sat-phone, both better than the small pop up antenna.  The small “pancake” style antenna is an improvement, but it was meant for a car roof and is not nearly as effective as the real rail or mast mounted cone. If you use the pancake, attach it to a steel pie tin to get counterpoise.  If the sat-phone is your primary communications system, go for the real antennaSailmail does not count internet, wi-fi or sat-phone data connection for the 90 minute connect time limit.  If your cruising plans take you beyond Hawaii you really want a well installed SSB; the sat-phone is a nice complement.)


Iridium has one great advantage: portability. Pack the phone into a small waterproof Pelican case and store it with your grab-bag. Then, if all else fails, you can always call the Coast Guard on the phone. Note however that Iridium phones are NOT waterproof, and to call someone you need to know the phone number.

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