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Installing an HF SSB and a Pactor modem

Oct 1, 2009

There are many communications options for the voyaging mariner. One approach is using a high frequency single sideband (HF SSB) radio and a digital modem. This setup allows you to use the SBB for voice and for sending e-mail. Icom's latest marine SSB transceiver, the model IC-M802, is popular with the voyaging community, as it is legally usable without modification on both the marine HF and amateur radio HF frequencies (with appropriate licenses). Combine this radio with the SCS Pactor modem, and world-wide e-mail is a reality.

If you are contemplating the purchase of an SSB transceiver, the Icom IC-M802 is worthy of consideration. No license is needed for installation and commissioning of the radio and Pactor modem, but if you have no prior experience with radio installation, purchase the package from a dealer who can provide installation and commissioning services, as this is not an appropriate learner's project. If you feel that you are ready for the challenge, it's a good idea to shop around on the Internet for the best deal that you can find. You are advised to get help from someone who has installed and commissioned the same equipment, no matter what you purchase. The steep learning curve that you will be facing in this endeavor is quite a challenge when faced alone.

The IC-M802 consists of three parts: 1) the radio controller or display unit 2) the external speaker and 3) the radio main unit or electronics. The handheld microphone plugs in to the controller. Prefabricated 16-foot cables are supplied to connect the controller and external speaker to the main unit. None of the three parts are weatherproof, so they must be mounted in protected areas. Mount the main unit as near to the external antenna tuner as possible.



Antenna tuner connections

Icom recommends the model AT-140 tuner, but the model AT-130 tuner will work just as well. Internally, the difference between the two is that the AT-140 has a separate dedicated tuner circuit for 2,182 KHz (the emergency frequency) should the automatic tuner fail. Externally, the AT-140 has the coax and tuner cable connectors on short pigtails, making for a much easier set up. Connect the main unit to the tuner with a marine quality coaxial cable such as Ancor RG-213 and high quality PL-259 UHF silver and teflon coax connectors for minimum signal loss. If you are not familiar with soldering these connectors, high quality compression-type connectors are available and their use is recommended. A second coax connector is provided on the radio for reception of digital selective calling (DSC) transmissions. This is a receive-only circuit and any 50-Ohm marine coax cable such as the smaller diameter RG-58U can be used. Simply terminate the coax on a chainplate. The IC-M802 tuner control cable plugs into the main unit and the pigtail connector on the AT-140 tuner.

Install a T-4 ferrite isolator (www.radioworks.com) or MFJ-915 (www.mfjenterprises.com) in the coax at the tuner. This device prevents radio frequency energy from flowing along the outside of the coax shield, and thus eliminates radio frequency feedback into the radio. Place a small amount of electronic silicone grease on each coax connector. Wrap the coax connectors with Coax Seal to exclude moisture.

While mounting yokes are provided for the controller and speaker, you must purchase the Icom flush mount kit MB-75 or construct panel mounting brackets if they are to be mounted as shown in accompanying photo.

The IC-M802 is provided with a power cable in which there are two 30-amp in-line fuses. Best practice is to connect the power cable directly to a dedicated battery to minimize conducted noise. This circuit should be protected by a 25-amp circuit breaker in the positive lead and placed in an easily accessible position. The radio has a temperature-controlled crystal oscillator for extreme frequency stability. This element consumes power even when the radio is switched off, so it is important to open the circuit breaker when the radio is not in use to avoid unnecessary power drain.



Grounding and antennas

There is considerable information available on these subjects of grounding and antenna requirements and they are identical for all radio installations. Suggested reading is the SailMail primer downloadable from www.sailmail.com. Isolating capacitors installed on the copper grounding foils are highly recommended, see the section on grounds in the SailMail document. After installing these isolating capacitors, the service life of the zincs (anodes) on my boat was extended by an additional six months. Buy them from www.digikey.com as part number P4911-ND 0.15 microfarad monolithic ceramic capacitors.

Power up and configure the IC-M802 before going on to the Pactor modem.

GPS can be connected to the IC-M802 to automatically transmit your position when the DSC feature is used. The connector is on the radio main unit and the circuit is opto-isolated internally. Connect the NMEA data + pin to the center conductor.

The IC-M802 comes programmed with all ITU marine channels. A licensed technician must change these marine channels. Spare channels can be easily programmed with your favorite ham frequencies if you are appropriately licensed.

Select a working frequency and press the "Tune" button. You should hear the relays cycling in the tuner and the "Tune" symbol on the display should flash, indicating that a solution is being calculated. If no relay clicking is heard and/or "thru" is displayed, then do not transmit as damage may occur. Review the tuner cable connector first as it is the usual source of trouble. Measure the voltages at the radio and also at the tuner end of the cable (they should be the same):

Looking at the connector on the radio, from left to right:

1. Key (yellow or white wire): about 7.5 V DC to ground and to -0.5 to 0.8 V DC during tune. (If more than 8 V DC, move S1 in the tuner to "off" (bottom position.)

2. Start (Green wire) to ground: about 7.5 V DC &mdash it must go to less than 1 V DC to start tuning process.

3. Red wire: supply voltage: 12.6 V DC up to 13.8 V DC.

4. Black or brown wire to ground: zero voltage.

5. No connection.

6. No connection.

Once you are satisfied with the transmitting and receiving functions of the IC-M802, then proceed with the installation of the Pactor modem. Be sure to observe good operating practices and listen for a clear frequency before tuning or transmitting.

Install the SCS Pactor modem near the radio controller where it can be easily seen while operating the radio. It has no front panel external controls so it can be located behind a transparent protective cover.



Connecting cables

Four cables are required for the modem:

A serial or USB cable to the computer (depending on the model purchased)

A control cable from the modem to the radio main unit

A data cable from the modem to the radio main unit

A power cable for the modem &mdash as an option, power can be supplied via the data cable.

Begin by drawing out a connection diagram or schematic. Write the cable lengths on the diagram and use it as a check list to keep track of the cables, connectors and ferrites. Route the cables as far away as possible from transmitter coax cables and alternating current-carrying conductors. Measure the lengths carefully, and allow at least 10 percent excess.

Construct the cables per the cable diagram. To prevent interference, shielded cable must be used without exception. Tin the ends of the conductors prior to soldering them to the connectors. Use a mating half of the connector to act as a heat sink and to hold the pins in position during soldering. Work quickly to avoid overheating the connectors. Carefully inspect your work to insure that no solder bridges or wire fragments short circuit one pin to its neighbor. Remember to solder the drain wire to the shell of each connector. Complete the cable assembly by checking for continuity end-to-end on each conductor. Also check to ensure that there are no connections between conductors or to ground.

Have a second set of eyes review your work, as no second chances are granted in electronics.

Place a small amount of electronic silicone grease on the connectors and connect all of the cables. Install a clip-on ferrite on each end of all cables. A small nylon cable tie around the cable will keep the ferrite close to the cable connector.

Download and install a copy of SailMail software from www.sailmail.com, which also contains an up-to-date station and frequency list. Obtain your subscription for one year service at US $250. If you are a licensed ham operator, download a copy of Airmail from the same site. Consider sending a small donation to the ham operator of the station that you connect with to help defray his expenses for providing this free service to you. (It's certainly not free to him!)

Connect the serial or USB cable from the modem to your computer, power up the modem and start the SailMail program.

Power up the Icom IC-M802, select a quiet frequency, set the radio to "mid" power, press the tune button to activate the antenna tuner. Set the PTC output from the "terminal window": Go to "tools" à "options" à "xmit unproto fsk." Set the output to four bars (1/2 full output). Then to to "xmit unproto psk" and set the output to four to seven bars. Do this very quickly!) Radio current draw is not a good indication of voice output. Give a long verbal "AHHHHH…" into the microphone. Do this quickly &mdash just a few seconds is sufficient. The display unit should show eight bars. Read the "Application Note on Setting Drive Levels" in the SailMail primer for more details.



Sending your first e-mail

SailMail allows you to import your address books from other e-mail programs, or you may manually enter the details. Compose your message as you would with any e-mail program. Click on the right most icon on the toolbar to bring up the message page. Select a station from the drop down menu, logically, the one nearest your location. Next, click on "mode" and select "scan frequencies." This directs the SailMail program to order the IC-M802 to sequentially scan the available frequencies for that station. Listen carefully for a buzzing or chirping sound characteristic of Pactor traffic. Select the frequency with the strongest sounding signal, generally the lower frequencies at night and the higher ones in the daytime. Before transmitting, wait until the frequency is clear (quiet). The sending station will sometimes end its transmission with its call sign in Morse code. Set the IC-M802 to "mid" power (about 60 watts). (Never use full power. FCC regulations require you to use only sufficient power to complete your communications.)

Click on the "send" icon, and the radio will begin to transmit. After 20 or so cycles, the radio will stop transmitting if no connection is made. You will learn to disconnect after about 15 or 16 cycles if no connection is made. Either a distant station is using the frequency or propagation is insufficient on that frequency to secure a connection. Try the next higher or lower frequency or try again on another station. Once connected, message transmitting and receiving is fully automated with no operator intervention.

Before leaving the dock, turn on your autopilot and transmit on your new Icom IC-M802 at full power. If this radio transmission causes your autopilot to behave erratically, then you have a radio frequency feedback problem. Review your radio installation, paying particular attention to the antenna ground foils. Also, install a ferrite on the rudder position transducer cable at the transducer. Make sure the problem is fully solved before dropping your mooring lines.

If all else fails, find a fellow voyager experienced with SSB radio and e-mail and ask for his help.

A note about the "e-mail" button on the IC-M802 and the preprogrammed e-mail frequencies: Ignore it all. They have nothing to do with this setup. n



Harry Hungate (N1UDE/ZL1HAH) and his wife Jane Lothrop (AB0T/ZL1JRL) live aboard their Corbin 39 Cormorant having departed Annapolis, Md. in 1997. Both are amateur extra class hams and Harry holds the FCC GROL with radar endorsement license. They cruised the west coasts of SE Asia in 2008 and they plan to transit the Indian Ocean and Red Sea in early 2009.



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