VHF radios have come a long way in the last few years. Today, radios can be equipped with integrated chartplotters, GPS displays, integrated hailers and fog-horns, remote transmitters, remote mics, different colors, and having so many advanced features that it almost makes the selection impossible. Therefore, no radio installation would be complete without at least some discussion on what all of these features mean, and which ones are important to you.
While there are articles that provide head-to-head comparisons, it is likely that not all of the features can be discussed. And it also seems new radios are always coming to market - therefore, the only real way to assess which radio is for you is to conduct your own research. Fortunately, most of the radio manufacturers have both brochures and owners manuals that you can download to do your own market research.
I'll not try and provide an exhausting description of every specification the radio has, but rather, concentrate on those that are important.
Output Power: Virtually all fixed-mount VHF radios transmit at 25 Watts, with the capability to switch to 1 Watt. Some VHF marine channels are restricted to 1 watt operation, and the radio automatically switches to low power mode when these channels are used.
Watts are the measurement of power - and can be likened to Horsepower. A more powerful radio will likely provide longer distance communication - up to a point. VHF is Line-of-Sight - which means that the distance will be limited by the curvature of the earth. So one should realize that antenna height plays an important role in transmitting distance.
Receiver Sensitivity: Usually specified as microVolts (µV) at SINAD (Signal to Noise And Distortion), and specifies how weak of a signal can be captured. Fortunately, the major players all rate their radios using a 12dB (decibel) SINAD. This is a technical reference that describes a signal that will be distinctly heard above the background noise. The signal will be noisy, but it will be heard. In some cases, you may even find a specification of 20dB SINAD, which means the signal is much stronger than the background noise, so much so that it is considered "Full Quieting". However, comparing signal strength specifications with some radios given in 12dB and some at 20dB is an Apples-to-Oranges comparison. Therefore, for the comparison to have any meaning, the SINADs for each specification must be the same. FYI, a rating of 12dB means the signal is 20 times louder than the background noise, while 20dB means the signal is 100 times louder.
A typical sensitivity specification might be 0.25 µV@ 12dB SINAD, which can be interpreted as; the receiver can pick up a signal as weak as 0.25 microVolt signal (0.00000025 of a Volt), even though it might be a bit hard to hear from the background noise.
When comparing receivers, a lower rating is better. Therefore, a receiver having a 0.22 µV @ 12dB SINAD sensitivity will be just a bit better than one having a 0.25 µV@ 12dB SINAD. If you were comparing two receivers having these specifications, the reality is that while differences might be measurable in the lab, you won't likely notice any difference at all.
You might see a receiver with a sensitivity without the SINAD portion, or a different SINAD. For instance, sensitivity might be simply: 0.25µV. Without a consistant SINAD, you cannot accurately compare the two receivers.
Audio Output: Usually expressed in Watts of audio power. This can be important. In a typical boat, engine or wind noise can produce a significant degree of background noise, and if the audio section is not up to the task, it may be difficult or impossible to hear. Just as important is the size of the speaker, and where you locate the radio.
DSC: As of 1999, all new radio models obtaining FCC approval must have a basic Digital Selective Calling (DSC) functionality. There are two components to DSC, emergency and non-emergency.
DSC is a function that provides an emergency signal to the US Coast Guard. For DSC to work, you must provide a GPS input to the radio, typically using a NMEA 0183 connection. Most, if not all GPS chartplotters have this output, but basic GPS units (non-chartplotters) displays may not. You must also obtain a MMSI number (Maritime Moble Service Identity). Boat/US, in an agreement with the FCC and US Coast Guard, provides MMSI numbers to recreational boaters free of charge. MMSI numbers are available from the BoatUS website. A MMSI number is a unique identifier for your radio, and can be likened to your radio's "phone number".
When you obtain your MMSI number, you must enter information into a database, including the boatowner's name, address, emergency contact information, vessel name, registration, home port, as well as any other information you wish to provide, such as boat size, manufacturer, size, color, and so on. This is your emergency information. You then program your DSC equipped radio with the MMSI number.
If the occasion occurs that you have an emergency on board, the emergency DSC function is typically activated by an emergency pushbutton. When you activate the button, your current longitude and latitude from the GPS chartplotter and your MMSI number are broadcast on VHF Channel 70.
The US Coast Guard program for DSC is called Rescue21. If the US Coast Guard picks up this signal, they look up your MMSI number in their database, and instantly know who you are, what your boat looks like, and your current position. Obviously, this information is critical in saving your life at sea.
Unforunately the Great Lakes are one of the last areas in the country to receive this service. The implementation schedule is in the 2009 ~ 2011 time frame. More information about the US Coast Guard's Rescue 21 can be found at: www.uscg.mil/rescue21
Squelch: A feature all radios have, it mutes the channel whenever there are no conversations, which alleviates having to listen to the annoying background noise. Some squelch controls set by the use of a rotary control while others are set by up and down buttons. Which type of control is up to each boater's personal preference, but I prefer the rotary knob.
Channel Selector: Changes the radio's channel. Like the squelch control, the selector may be either a rotary knob or up and down button. Again, this is personal preference, but I much prefer a rotary knob, which are generally found only on the higher-end radios.
The term higher-end is almost a misnomer. There is so much competition in the VHF Marine radio market that virtually all of the popular radios are within a range of $150 to $300, and easily within the budget of the typical boater.
Up until now, we concentrated on the basic features every radio should have. The discussion will now turn to advanced radio features that you may wish to consider. The radio you are considering may or may not have these particular features.
Form Factor: While most radios still are designed to be either gimbal or flush mounted, several new radios have recently been introduced that consist of three separate components. The electronic box, which houses all of the radio components, a handset, and a speaker. The handset contains all of the radio's controls and display. The advantage of this radio is for those of you that do not have sufficient helm space to mount a radio. All you have to find room for are the handset and speaker. Standard-Horizon's PS 1000, PS 2000, and RayMarine's Ray 240 are examples of this.
Scanning: While most sophisticated radios have a scanning feature, some basic units do not. Scanning is a process whereby each receive channel is scanned in sequence, not unlike a "police" scanner. You generally have the ability to lock out selected channels as required so that only those channels you are interested in are checked. Most scanners have a priority system as well, in that either or both channel 16 and channel 9 are scanned more frequently that other channels. For example, one method might be to scan channel 16, then scan channel 1, scan channel 16 again, then scan channel 2, and so on.
DSC Part 2: In the first section, we only discussed emergency DSC functionality. While for the Great Lakes region this is not yet supported by the USCG, there are other DSC functions that are available now. One such function is the "buddy list". If you were to program in the MMSI number of your fellow buddy boaters, you could contact them via DSC. The basic operation goes like this: You select your buddy from your list of MMSI numbers programmed in your radio. The radio then attempts to contact your buddy using DSC channel 70. If your buddy is in range, and their DSC radio acknowledges your radio's request, both radios will find an unused channel, set both radios to that channel, then notify both parties. This alleviates having to search multiple channels for your buddy when you are hauling those big fish in. Some radios, if so equipped, may even display your buddy's GPS coordinates on your display.
DSC Polling: A feature more and more radios are including is called DSC Polling, or DSC Location Polling. It takes the buddy list a step further. In this scenario, you select your buddy from your list of MMSI numbers, and the radio makes the same setup. However, if you have a properly equipped GPS Chartplotter, the radio can instruct the chartplotter to plot your buddy on the chart, and even setup a course, and display bearing and distance!
Icom has a very nice set of tutorials explaining DSC basic and advanced features DSC Tutorials.
DSC Class D: The last enhanced DSC feature to be discussed is Class D. This essentially refers to a separate receiver built into the radio just for DSC channel 70. For a non-Class D radio, if you were engaged in a conversation on another channel, you may miss a DSC poll from a buddy. But since a Class D radio has a separate receiver for this function, you will receive buddy polls regardless of your current activity.
GPS and Chartplotter integration: You can even buy a radio that integrates a GPS chartplotter and a VHF DSC radio. This is a very cost-effective solution, compared to purchasing separate components, especially for a small boat that might not have room on the dash for both units. And there is no chance for improperly wiring the two units together. Standard Horizon's CPV350 is an example of a highly integrated all-in-one GPS/Chartplotter/VHF radio. You can even add a fish-finder to this radio!
Enhanced Display: Would you believe that some of the more basic DSC radios don't even display either your LAT/LON position, or the distant radio's position? For these radios, the only indication you have a GPS connection may be a "GPS" label. This radio is only useful for the most basic DSC emergency function. I would highly recommend any DSC radio you are considering at least display the LAT/LON.
Radios such as Uniden's UM series radios, when connected to a chartplotter, can duplicate the basic GPS display on the radio, including not only latitude-longitude (which many other radios do), but also a compass display, bearing, track, speed, heading, and even a rolling "road-map".
Foghorn, hailer, external speaker: Another popular feature is a foghorn/hailer/external speaker. This requires the wiring of an external PA type speaker on the boat, and your ability in finding an aesthetically pleasing location for the speaker will weigh in on this option.
Remote mic (wireless or wired): The last advanced feature is whether or not you desire a remote mic. This is likely going to be more of a need for a saliboater or powerboater with dual helm stations. Remote mics may only have a few basic features, or they may duplicate all of the features of the radio, including the display. Some may even have an intercom feature so that a 2-way conversation can take place between the flybridge and lower cabin. Uniden even offers a wireless remote mic on some models.
Which one to select: Are you confused yet? You bet. There are so many features and options to be found on the modern VHF Marine radio, with many manufacturer brands competitively priced, it becomes quite difficult to choose which one is for you. But like anything else, it all comes down to your basic needs. Does the radio offer a flush-mount? Do you prefer a knob or up and down switch to change channels? Do you really need all of those functions, or just concentrate on what you really need?
Assuming you have waded through all of the brochures and made a selection of radio, its finally time to install it. Again, some decision making must take place.
Location. Before choosing a permanent location for the radio, keep in mind that the receiver's speaker should be pointed towards the operator. For reasons indicated above, many boats have a lot of background noise, and the operator may otherwise have difficulty hearing conversations. In addition, some radios require there be a minimum distance of 1 Meter separating the radio and antenna to ensure proper operation. Again, check the owner's manual prior to cutting.
Gimbal or in-dash flush mounting. I prefer in-dash mounting, but it does take more time and effort to do so. However, some boats may not have sufficient dash space for flush mounting. If you have the choice, check with your insurance company - some policies may not cover any electronics that are not flush mounted.
When flush mounting the radio, you must often purchase an optional flush-mount kit from the manufacturer. While most radio models have this capability, some do not. Also keep in mind that connections and wiring will exit the back of the radio, so be sure to allow for that additional space. In addition, many radios have a heat sink for the transmitter section to draw heat away from the RF Amplifier. You must allow for air flow around the heat sink as well. Check with the installation instructions to determine if there are any dimensional requirements.
Measure Twice, Cut Once
So we've picked out the radio, bought the flush-mount kit, determined a suitable location, and we're ready to cut. Well, not quite. I always like to use the phrase "Think Twice, Cut Once", which is my version of the cliché "Measure Twice, Cut Once". I just think this has more application here. You want to think about what you are doing; have you thought of everything we have discussed here; location, clearance, and the ability to access the unit from the rear?
Go through the installation instructions if you need to - step by step - in your mind, so that you do not forget anything. It is very difficult to patch a big hole in your dash, so be sure you have thought about everything for awhile.
So now its time to cut. I always like to layout my cuts with "blue tape" and a permanent marker. This not only allows you to layout where to make the cut, the blue tape protects the underlying surface from scratching. If possible, remove the panel when you make the cut. Panels are typically made with some amount of aluminum in them, and you want to minimize the metal shavings that get thrown in to the backsides of your switches and gauges.
If you cannot remove the panel, use blue-tape and cover up both the front and back of all of the nearby switches and gauges.
My instrument of choice for making cuts is a jig-saw adaptor for a Dremel rotary tool. I have also had good luck with a pneumatic version, but this requires an investment in an air compressor, and the ability to get the compressor on site. Often you are at the limit of the Dremel's capability, and it may be prone to overheating. So take it easy, and take it slow or you may end up burning up that Dremel tool.
If you drill a pilot hole (larger than the diameter of the saw blade) at each corner of the cutout, you will not have to negotiate any sharp turns.
Once the cutting is finished, you will likely want to go around with a file and clean the cuts a bit. If it looks a bit ugly - that is OK, as long as you did not go outside of the lines; nothing will show after you install the radio.
If you are installing a DSC-equipped radio, you will need to connect it to a GPS signal source. The GPS signal could come from a standalone GPS receiver, such as a RayMarine RayStar 125, a GPS chartplotter, or multifunction display. Regardless of the signal source, the GPS must have a NMEA 0183 (National Marine Electronics Association) output. There are proprietary exceptions to this, but unless you are sure of otherwise, both the VHF radio and GPS will have NMEA 0183 inputs and outputs.
You may want to review my NMEA-1083 Tutorial for an in-depth discussion of NMEA-0183 connections.
When interconnecting cables, my preference is to use a terminal block rather than simply hard wiring (soldering, crimp connectors) the cables together. This allows for future reconfiguration, should it be necessary. For interconnecting the chartplotter to the VHF radio, the chartplotter's NMEA input should be connected to VHF radio's NMEA output, and vice versa.
Since the radio is part of my boat's integrated helm system, I will be using the NMEA 0183 output from a RayMarine C-80 multi-function display to provide longitude and latitude information to the radio. In the future, I will likely have more devices requiring NMEA0183 data, which will require the use of a NMEA interconnect device that supports multiple signals (typically called a multiplexer or hub), so using a terminal block allows these changes to be easily made.
Even with a helm the size I have, often a compromise must be made as to where items are mounted. This area is directly behind the radio and chartplotter, and was chosen rather by default, since the supplied connectors were too short for another location.
The remaining connections consist of connecting 12VDC and a ground to the boat's grounding grid and the antenna connection. I plan on a future addition of a PA speaker for the foghorn/hailer function, as soon as I can find an appropriate location for the speaker.
For the antenna connection, I prefer to use Shakespeare brand "CenterPin" solderless connectors rather than the connector that typically comes with the antenna. After many years in the electronic industry, proficient in the soldering method, I find the CenterPin connectors very desireable, and literally foolproof. You cannot easily reuse the connectors though, so don't install one until you are sure you have pulled the coax completely through the boat.
Antenna installation is a topic all in itself and can be found here: VHF Antennas.
Once power is applied to the system, make sure that you can see GPS coordinates on the VHF radio's display - if it has that function. If you have a buddy with a DSC radio, you can try out the "buddy list" feature of the radio, and if so equipped, the DSC Polling function.
I also added an external hailer that connects directly to the VHF radio. The hailer is essentially a loudspeaker that has two functions - both controlled by the radio.
Finally, I added a Remote MIC-III to the radio, whch allows me to control the radio from the salon. This is useful if I want to get the day's weather report without having to go to the helm.
At this point in my system integration, I have a multi-function display, consisting of radar and GPS sensors, and VHF radio interconnected.
US Coast Guard Rescue 21.
Boat/US MMSI program.
RayMarine VHF Radios
Icom Marine VHF Radios
Standard-Horizon Marine VHF Radios
Uniden Marine VHF Radios