Radio
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- The category of the whole exercise [weather information collection] will be greatly enhanced by weather reports received from the outside world. This information comes by radio in various ways, transmitted by stations around the world. The stations and their frequencies are listed in a government publication Worldwide Marine Weather Broadcasts….the quality of the results from a radio weather broadcast can depend on the crew’s knowledge as well as the type of radio instrument that is used. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 216)
- Professional help will pay off handsomely in all phases of radio installation, and not just in jobs where it is required by law (such as setting up of a sideband radio). From the planning stage right through post-installation calibration, an owner will be fortunate to secure the best help available. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 224)
- The two principle means of communication for boats at sea are VHF (Very High Frequency) and SSB (Single Band) radio telephones.
- Electrical noise, or “static”, is the cause of much poor performance in both Loran-C and radio reception. Such noise can come from the outside, generated by lightning or other external electrical phenomena, or it can be generated onboard the boat by various pieces of equipment – for example, motors and alternators. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- See image in Desirable and Undesirable Characteristics of Offshore Yachts p. 228 for steps to limit noise
- Usually, the on-board static producers will include one or more of the following objects: pumps, alternators and their regulators, refrigerators, motors, computers, Loran-C receivers, flourescent lights, engine instruments, and loose connections. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 228)
- ….“static” and “electrical noise” are two very different things. The antenna either connects to (DC) ground in which it won’t build up static, or it floats above (with a higher voltage than) ground and so can hold onto a static charge. It can be caused by wind blowing on the antenna, snow or other factors. Electrical noise is RF pulses or their harmonics generated by equipment onboard. Such equipment may contain spark gaps (as in electric motors) or oscillators (switching power supplies) or diodes (alternators, battery isolators, triacs/dimmers) all of which can generate RF which then leaks into your receiver. This can be prevented by proper EMI shielding and RF choking on electrical lines. (http://www.reddit.com/r/HamRadio/)
Antennas
- Good antennas are basic to obtaining proper performance from electronic equipment on boat….require occasional maintenance, can cause windage and involve appreciable expense…careful planning of the system is well worth the effort. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 226)
- Some equipment (VHF-FM, Loran-C, radar, satnav, and Omni) run on special-purpose antennas, one for each instrument. On the other hand, SSB, ham, radio and the communications receiver are all able to operate on the same HF antenna, using a switch so that one instrument is in use at a time. The classic HF antenna, are the insulated permanent backstay, the long whip…. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- …adds up to a lot of antennas, and unfortunately, a yacht – particularly a sloop or a cutter – has a limited number of locations for them. All you can do is grit your teeth and find a place for them where they will operate properly. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- The higher the rated gain of your antenna, the longer the range, and the narrower the beam. The transmission range, however, depends more on the height of your antenna than any other factor, including wattage. The higher the antenna, the greater its “line-of-sight”. The only way to legally increase the sending and receiving power of your marine radio system is to use a longer antenna with more gain.
- Gain is the ability of an antenna to amplify both outgoing and incoming signal power. It’s a function of how much the antenna focuses the energy of the signal in a horizontal direction. When gain (measured in decibels, or dB) is increased, the normally oval radiated power pattern becomes more oblong and horizontal, reaching out further toward the horizon. Increasing gain increases your signal power geometrically: a step from 0dB to 3dB will double your signal’s power, while a step from 3dB to 6dB quadruples it. Higher gain also means a more narrowly focused beam, which can cause the signal to fade in a rolling sea. The more stable your boat’s platform, the less it rolls, and the higher the gain you can effectively use. (www.boatus.com/boattech/antennas.htm)
- Coaxial cable is specially designed to transfer your radio signal to your antenna with as little power loss as possible. Use the largest 95% shielded coax that fits to reduce signal loss between the radio and antenna. PVC-coated (not plastic) cable RG-58 and RG-8X, frequently supplied with the antenna, are fine for cable runs up to 25′. For longer runs, use low-loss cables such as RG-8 or RG-213. RG-8U is not recommended for marine applications because it is foam-filled and will collect moisture, creating loss and quickly corroding the cable inside. Keep the cable run as short as possible and avoid sharp bends, kinks, or strains to get the most from your system. (www.boatus.com/boattech/antennas.htm)
- The ferrule is the bottom fitting on the antenna that threads into your antenna mount. A plastic or nylon ferrule is fine on small boats for light use in calm or moderate waters. If your antenna is subject to more flexing because you cruise or fish in all types of weather, you’ll need a more durable metal ferrule. Match antenna mount and ferrule materials, that is, nylon with nylon and metal with metal. For extra strength and longer life, use stainless steel mounts or chrome-plated brass with a chromed antenna. Use silicone spray regularly on both the ferrule and the mounting threads to prevent corrosion. (www.boatus.com/boattech/antennas.htm)
- The connection between your radio and antenna is critical to your VHF system’s operation. If you must splice the cable, use proper PL-259 connectors to reduce loss. Use a silicone protectant spray or clear semiconductor heat shrink compound, and wrap them in Ancor Marine Grade – heat shrink tubing or quality vinyl electrical tape to prevent moisture intrusion, which will corrode the copper braid in the coax. Immediately seal up any nicks in the cable and antenna to keep moisture out. If you must solder, use proper soldering techniques and at least a 30-watt soldering iron and 60/40 rosin core solder. This job is not difficult, just exacting. (www.boatus.com/boattech/antennas.htm)
- There is….no advantage to elevating antennae receiving signals from overhead satellites. To the contrary, the higher you mount a GPS antenna the less accurate the speed and directional information will be because the antenna will be whipping around due to sea conditions. GPS antennae should be as close to deck level as possible while still maintaining an unrestricted “view” of the sky. (This Old Boat, p. 300)
Antennas – High Frequency Single Side Band (HF-SSB)
- Since the ocean is a fine ground and is right there, you would think that grounding would be easy….it is not…the reason for this is that HF currents are very particular about what they run through. Conductors that would be prefect for carrying direct current (DC) or low-frequency current (AC) may be poor for HF current. even more strangely, grounds that work for one kind of antenna tuner or coupler may not always work with another kind. A ground system may be built into the a fiberglass hull…it must be carefully designed…require substantial work. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- The HF antenna must be tuned by an antenna tuner, or coupler which is usually located where the antenna leads into the boat. Without the coupler, the set will not operate properly and good be damaged. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- Today’s automatic couplers, which sense the frequency coming from the transmitter and tune the antenna to it, can sense the frequency coming from the transmitter and tune the antenna to it, can efficiently match the multi-channel capability of the newer synthesized transmitters. A coupler can also be used on a ham radio set, although most ham operators prefer to tune manually. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- When HF antenna system is used for a communications receiver, the coupler should be left out of the circuit since it will sometimes taken the incoming signals (by itself, the receiver will not actuate the coupler). Either switch the antenna directly to the receiver while receiving transmissions, or set up a separate receiving antenna altogether using a length of wire hoisted aloft. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 227)
- An insulated backstay often doubles as the SSB or ham radio antenna. Note that on a fiberglass boat, a lower insulator is unnecessary as long as the backstay chain plate is not grounded to the boat’s grounding system. During transmission, the energized antenna can burn you, so insulate the bottom ‘ of the stay with a rubber hose (Sailboat Electrics Simplified, p. 65)
- The connection to the stay is made…using stainless steel cable clamps. The wire is typically antenna lead-in, held clear of the stay with stand-offs…but if you elect to use coax instead, be sure only the center conductor is in contact with the stay, not hte brad. The entire connection should be protected from the weather by coating it with electricians putt (Coax Seal), then wrapping it from the bottom to top with self-amalgamating tape. (Sailboat Electrics Simplified, p. 65)
- There is also generally little point in mounting an SSB antenna above deck level. Although ground transmissions over a short distance may benefit from additional antenna height, long-distance SSB transmissions are accomplished with sky waves. Antenna length is critical, but the height of the antenna has little effect. (This Old Boat, p. 300)
Communications Receiver
- If two-way communication is not important or if the crew wants to receive more elaborate weather information than that provided by SSB (as well as news and music on the AM broadcast band, which is not available on SSB), a versatile type of radio called a communications receiver offers excellent service….In their best form, these HF receivers with many special features that allow them to receive both voice and code transmissions even in unfavorable conditions. Besides variety and compactness, the hallmark of these receivers is their clear reception, due first, to their tuning accuracy, and, second, to controls that allow the operator to select the bandwidth – music requires a lot of bandwidth, voice somewhat less, and code least of all…these controls include a two-position bandwidth switch labeled “music” and “news” and a mode switch labeled “normal” and “SSB” which allows fine tuning with a thumbwheel. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 218)
HAM Radio
- Another method of long-distance communicating is the amateur or ham radio. A special Federal Communications Commission license is needed to operate a ham instrument, but the effort of studying for the license may well be worth-while for an offshore sailor, since this is a very effective means of communication. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 218 )
- Ham has four big advantages: (Desirable and Undesirable Characteristics of Offshore Yachts, p. 218 – 9)
- The transmitter, if desired, can be operated at a higher power than marine-band transmitters, and has at least as long a range.
- A sailing ham can make telephone calls by “patching into” shore ham stations, thereby bypassing crowded marine telephone stations (by law, the call cannot be used for business and other specified purposes).
- A ham installation is less expensive than marine SSB installation.
- It is very versatile; the latest generation of ham radio transceivers can function as high-quality, general-coverage communications receivers, thereby serving many of the purposes served by the other instruments that we have already mentioned.
- Although HAM radio has been used for successful distress calls on many occasions, it should not be regarded as a substitute for a marine SSB, since nearby commercial vessels will not be carrying ham radios and the Coast Guard does not continuously monitor ham frequencies, as it does with SSB and VHF. However, by arranging radio appointments at a given time and frequency, a sailing ham operator can set up a system by which friends ashore on other vessels can follow the boat’s progress and be aware of developments, good or bad. There are also volunteer “marine nets” that operate on certain frequencies by common usage; their members are delighted to help yachtsmen. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 219)
- One limitation for cruising sailors is that a vessel generally may not operate on ham bands within the territorial waters of a country that is not her country of registry, unless she is licensed in that country. This means that, for all practical purposes, ham radio is used by sailors only on the high seas in waters of the country of registry. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 219)
High Frequency Single Side Band (HF-SSB)
- The basic deep-sea instrument for picking up weather broadcasts and communicating is the high-frequency (HF) single band radio-telephone (SSB). An SSB is expensive and may remain so due to some built-in costs: its system is complex and its frequency tolerance must be very tight. One alternative is to SSB is direction satellite communication. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 218)
- …can bend around the earth for a distance. Also very important capability of going to levels high in the atmosphere, where they are reflected back to a point far from the origin of transmission. This means that HF is good for very-long range communication. Since the atmospheric reflecting layers are generated by sunlight, the ability to communicate from one given point to another depends upon the time of day and other factors (among them, the number of sunspots and solar flares. The frequency also affects communications, and SSB instruction manuals list the range for each frequency Generally higher frequencies provide very long ranges, especially under the daytime. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 226)
- Techniques for operating SSB can be found in Desirable and Undesirable Characteristics of Offshore Yachts, p. 226
- The jump to SSB is a major one – in terms of cost, installation, sophistication of circuitry and operation. With the right equipment and atmospheric conditions, the range of an SSB radio is thousands of miles…regulations require the use of VHF whenever its range is sufficient to establish communications; SSB therefore can be used only offshore or in more remote areas of the world, but for the itinerant cruiser, it could prove invaluable. (Upgrading the Cruising Sailboat, p. 265)
- To view a chart of the different distance capabilities of radiotelephones, see Fig. 13-12 from Upgrading the Cruising Sailboat, p. 266
- Models range from 50W – 1,000W, but the largest are really intended for use only on large commercial ships. More power doesn’t necessarily mean greater range or clarity. More important is the user’s knowledge of frequencies, daily and seasonal effects and his ability to tune the set properly. With the improved solid-state circuitry available today, a typical SSB for the cruising sailor might be rated at 150W, and have the same range as the 1,000W sets. (Upgrading the Cruising Sailboat, p. 270)
- SSB frequencies begin with the Middle Frequency (MF) coastal bands at 2 – 3 MHz [this is actually incorrect, see wiki resource below]. From 4 – 22 MHz are known as the High Frequency (HF) or High Seas bands. High frequency transmissions result in groundwaves that huge the Earth, and are limited in range to about 150 miles, depending upon conditions and skywave propagation bounced off the ionosphere anywhere from 30 – 250 miles high. Under good conditions, you can get reception via skywaves up to 5,000 miles. There is a Skip Zone between the groundwaves and skywaves in which the SSB radio is ineffective. (Upgrading the Cruising Sailboat, p. 270)
- Typical frequency for the different reasons is showin in Fig. 13-21 of Upgrading the Cruising Sailboat, p. 270
- The effectiveness of SSB is very much dependent upon a good installation, and skilled technicians are required to do the job right. A ground plane must be established that may involve adding ground screens beneath berths, and tying together metal components (such as engine and tanks) inside the boat with woven copper straps. The antenna may be a whip type, or utilize the backstay or, on ketches, the triatic stay, both of which must have insulators no closer than 4’ from the mastheads on deck. An antenna coupler electronically charges the antenna’s length to match the desired frequency. The coupler, plus the radio itself, must be properly located and installed. While the time and money investment in SSB is considerable…we have received numerous stories from both ocean racers and crising folks about how SSB saved a life or expedited medical treatment. (Upgrading the Cruising Sailboat, p. 272)
- (To see a typical SSb installation, see Fig. 13-22 from Upgrading the Cruising Sailboat, p. 272)
- SSB picks up time signals (Upgrading the Cruising Sailboat, p. 272)
- More information about establishing an SSB ground plane can be found on the “Bonding & Grounding System” project page.
- Medium frequency (MF) refers to radio frequencies (RF) in the range of 300 kHz to 3 MHz. Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers (1,000 to 100 m). Frequencies immediately below MF are denoted low frequency (LF), and the next higher frequencies are known as high frequency (HF)…2182 kHz is the international calling and distress frequency for SSB maritime voice communication (radiotelephony). It is analogous to Channel 16 on the marine VHF band. Lastly, there are aeronautical and other mobile SSB bands from 2850 kHz to 3500 kHz, crossing the boundary from the MF band into the HF radio band (https://en.wikipedia.org/wiki/Medium_frequency)
Very-High-Frequency Frequency Modulation (VHF-FM)
- … provides reception of weather forecasts as well as two-way communications within the relatively small range of approximately 50 miles. The VHF transceivers on the market today are quite small and inexpensive, and very capable…best type to install is the “synthesized” instrumentthat provides communication on all channels plus the weather channels that, in the United States, receive continuous National Weather Service broadcasts. This type is immune from the bothersome, costly crystal changes that were necessary with early models to provide overage of many channels. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 216)
- When installing VHF, remember that since the signals travel by line of sight, the higher the antenna is mounted, the longer is the instrument’s range. Don’t be impressed by claims for “high-gain” antennas…they do not work well when a boat is heeled. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 216)
- A VHF transceiver is quickly out of range of weather stations when a boat heads offshore, and soon after that medium frequency commercial stations become increasingly hard to pick up. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 217)
- VHF signals almost always travel in a line of sight path from the transmitting antenna to the receiving antenna. Since the earth is curved, they can only go so far before the earth gets in the way. This is why VHF-FM radio , like television, is a short-range system. The actual distance the signals can travel depends on the height of the antennas, the higher they are the longer the path can be. (Desirable and Undesirable Characteristics of Offshore Yachts, p. 226)
- VHF radios are used by all types of commercial and recreational watercraft for ship-to-ship and ship-to-shore conversations. Their range is limited to line of sight, and so are used mostly for coastal cruising. (Upgrading the Cruising Sailboat, p. 265)
- Anyone who can operate a CB can operate a VHF. For calling the U.S. Coast Guard while cruising the coast, or talking to a fisherman or freighter passing by, its utility is unsurpassed. Fully synthesized types don’t use crystals – just dial the channel number and there you are. VHF radios are almost always mounted inside the cabin, such as above the navigation stations, or in the case of a smaller boat, under the deck or under a shelf on the bulkhead. The antenna is key to a good hook-up. Because the range of VHF is line of sight, the higher the antenna the farther the range. This means that a masthead antenna has a longer range than an antenna mounted on deck…For example, assume that the tip of a deck mounted antenna is 12’ above sea level…the distance in nautical miles is 12.1. A masthead antenna 44’ above sea level extends that range to 15.8nm – about 30% greater. (Upgrading the Cruising Sailboat, p. 266 – 7)
- For a chart that shows distance to object just visible on horizon, see Fig. 13-16 from Upgrading the Cruising Sailboat, p. 267
- When reading about VHF radios you usually see maximum distances of 25 – 35 miles. Several reasons exist for the discrepancies between these distances and the 12 – 15 miles just mentioned. First, a maximum range of 25 – 35 miles depends on good weather conditions, as excellent antenna installation and no obstacles – such as an island – between the transmitter and receiver. Second, radio waves do tend to curve slightly around the Earth’s surface. The distance to the horizon is determined by this formula: D = 1.144 x √H (where D is distance to the horizon and H is the height of the observer above sea level). The formula is difference for VHF radios based on the knowledge of how much the wavelengths bend. The difference formulas is about 22%, and this increases our previous figures of 12.1 and 15.8 to 14.7 and 19.3. (Upgrading the Cruising Sailboat, p. 268)
- The key to having a VHF that works at peak efficiency and reliability is the antenna hookup…Usually, masthead antennas are 3db gain and deck-mounted antennas 6db gain. The higher the gain, the longer the antenna, and the greater the range. However, the signal also becomes flatter and this can cause receiving difficulties in rolly seas. The distance from the antenna to the radio in part determine the size of cable needed – wire that’s too thin, run over a long distance, loses power. So, for 6db gain deck mounted antennas, about 20 fet of ¼” cable is provided. it is too small, however, for the 3db gain masthead antenna, which preferably ½” RG-8/Utype coaxial cable with a polyethylene core. (Upgrading the Cruising Sailboat, p. 268)
- The masthead antenna should be securely mounted on the side of the mast and the bracket provided the wire enters the mast through a hole, travels down to the base where it exists the mast again and passes through the deck, through the cabin and to the set. Rubber ferrules in the spar holes prevent cable abrasion. An alternative is to run the cable entirely in the spar. The choice is essentially whether you want the connections inside, out of the weather (but where any banging against the walls will be horrendous), or outside, where if a problem occurs – and it usually occurs at the connectors – it is more readily accessible. Some weatherproofing with silicone and duct tape over the conenctors certainly helps. (Upgrading the Cruising Sailboat, p. 268)
- See schematic of a proper VHF installation from Upgrading the Cruising Sailboat, p. 268
- …the closer the unit to the battery, the shorter the power wires and therefore the less potential power loss. For runs up to about 12’, use #10 AWG wire with crimp lugs or eye terminals, and plstic ties to hold them in place as you run them through the boat. The power wires can be led directly to the battery or to the main switch, but not the distribution panel, as too much power will be lost through the additional circuitry of narrow-gauge wires. (Upgrading the Cruising Sailboat, p. 269)
- VHF picks up the NOAA weather broadcasts (Upgrading the Cruising Sailboat, p. 272)
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