VHF radio (Technical)
DSC calling (Technical)
Wind (Technical)
Radar (Technical)
Depth & Speed (Technical)
Mini-M ()
Chart Plotters (Technical)
Inmarsat-C (Technical)
Inmarsat C terminals are a good safety resource onboard, providing free reception of satellite safety messages and weather, as well as worldwide text messaging via Inmarsat costing about 1 penny per character(including spaces).
The system connects to your laptop via a serial port or USB to serial converter and allows you to send short email messages and even small binary files like photographs, short videos and audio clips.
It is useful when all else fails, and you need to get a short message to someone via email from anywhere in the world, when you are out of cellular or GSM mobile phone range.
It can also be used for automated scheduled position reporting.
The older systems, designed for DOS, require special software like
Nebula to be used with PCs running windows.
You would need to set up an accounting authority to handle the billing for the service via one of Inmarsat's resellers, for the rare occasions when you might use it.
The system is required by commercial vessels under GMDSS certification and provides worldwide distress calling with position reporting. The system has a built in GPS that has an output that can be used to drive a chart plotter or other systems.
The system has two buttons, that if depressed for 5 seconds will send an international distress message with the current latitude and longitude.
In order to receive email messages, you need to set up permissions for friends and family to send to you. You pay to send and receive, so you don't want any unsolicited mail.
Inmarsat C is quite complicated to use, and it is essential to that your email is in the correct format for it to work.
Vizada has a new system called Skyfile C that is meant to simplify the process and allow Inmarsat to GSM messaging. Take a look at
Vizada.com for further information.
Howard [ Just Imagine ] 31-Dec-1969
Nebula Software (Technical)
Older Inmarsat C systems like the Trimble Galaxy Inmarsat C, that can be bought used from E-Bay and other sources, are designed to be run on DOS and need special software to run on windows systems.
This software, developed by Jim Corenman(developer of winmail SSB mail), can be purchased from
airmail2000.com.
Nebula is not freeware, and requires registration in order to be fully functional. Without registration, the download operates in a demo mode with Galaxy communications disabled. Demo passwords are available for a limited period via email (the address is in the Help/About window). The cost to register the program is US$50, payable by check to "Sirius Cybernetics" at the address in Help/About window, or by credit card via Fax: the area code is 360 and the number is 378-4392. Address the fax to "Sirius Cybernetics", include the usual credit card details and both your Inmarsat Mobile# (9 digits starting with a "4") and the 10-digit Inmarsat Serial# (on a label on top of the Galaxy box).
Howard [ Just Imagine ] 13-Mar-2008
SSB radio (Technical)
A radio ham friend that sailed with us, helped procure an ICOM IC-718 which is actually open to both ham radio and marine band frequencies. The radio cost $610 and the AH4 tuner cost another $247.
My career has been in communication electronics, I have a commercial FCC General Radio Operators License and I have learned Morse Code to at least 5 wpm several times over the last 30 years, but I have just never got around to doing the amateur radio license, so I have never had any need for the ham bands on the radio, but it cost a lot less than the marine band equivalent and it works great.
The only disadvantage over a marine only radio is that the all band radio is a little more complicated to operate, but once the presets are set you can memorize the sequence of which buttons to push.
Howard and Jayne [ Just Imagine ] 28-Jan-2008A rope antenna
Just Imagine must have lost the dedicated, separate, insulated stay antenna on the mizzen, before I purchased the boat. Only the lower turnbuckle and a piece of insulator remained.
Rather than replace it with another, heavy, expensive, stainless steel, insulated stay, or compromise the backstay with insulators, I came up with the idea for a rope antenna, based on the emergency antennas available in stores.
I bought a length of 7/16" braided line, and a length of RG8X (mini-8) coax. I removed the inner core of the braided line and replaced it with the coax for the length between the deck and the pad eye at the top of the mizzen where the old insulated stay attached.
The outer shield of the coax is used as the antenna (the inner core is not used) and only the outer braid connects to output lug of the antenna tuner.
The braided rope sheath provides strength and support for the coax, UV protection from the sun, and insulation both top and bottom from the mast and deck.
The coax comes from the output lug on the tuner under the deck, through a watertight deck fitting, into the braided rope about 4 inches above the deck, up the mizzen inside the rope, out at the top about 4 inches from the pad eye, and then up to the existing insulated triatic stay between the mizzen and the main. It was simply hose clamped on to the triatic and then sealed and rubber taped.
The top of the braided rope attaches to the pad eye near the top of the mizzen. There is a loop in the rope about 4 inches above the deck and the tail passes through the deck pad eye and through this rope loop several times so that it can be cinched up to take the slack out of the line.
I have only had to tighten this up once in the last 3 years despite everyone using the line as a hand hold. The antenna appears to be just another halyard.
The length of the wire alone would probably have tuned quite well without the triatic stay, but since it was there, I used it.
This worked extremely well, and I was able to communicate with Herb Hilgenberg in Toronto, all the way across the Atlantic.
The same braided rope antenna idea could be used on any boat, on a permanent or temporary basis on the main or mizzen. The SSB rope antenna could be hoisted on a halyard or flag halyard when needed and coiled near the deck when not in use.
I will try and find a photograph to clarify this simple and effective idea.
Howard and Jayne [ Just Imagine ] 28-Jan-2008
RTTY & Weatherfax (Technical)
JVComm32 Software (Technical)
No SSB installation is complete without an audio cable and JVComm32 shareware software installed on your laptop to provide you with WEATHERFAX, RTTY and NAVTEX. You can download the free evaluation version from
www.jvcomm.de/dlframee.html.
The unregistered. demo version will work fine, except for the deliberately annoying reminders that appear superimposed on both the weatherfax charts and the RTTY messages, and the annoying delay when you close the program down, reminding you that it is not a free program, and that you need to send USD$ 83.04 to Eberhard Backeshoff who has done a magnificent job developing this program in his spare time.
And, no JVComm32 installation is complete until you have registered and paid for the privilege of using this great product.
Howard [ Just Imagine ] 28-Jan-2008
Pactor Modem info (Please!) (Technical)
Can anyone please provide an overview about communicating with Pactor modem hardware and Winmail and Sailmail. Thanks.
Howard [ Just Imagine ] 13-Mar-2008
A Rope Antenna (Technical)
Just Imagine must have lost the dedicated, separate, insulated stay antenna on the mizzen, before I purchased the boat. Only a piece of the turnbuckle and insulator remained.
Rather than replace it with another, heavy, expensive, stainless steel, insulated stay, or compromise the backstay with insulators, I came up with the idea for a rope antenna, based on the emergency antennas available in stores.
I bought a length of 7/16" braided line, and a length of RG8X (mini-8) coax. I removed the inner core of the braided line and replaced it with the coax for the length between the deck and the pad eye at the top of the mizzen where the old insulated stay attached.
The outer shield of the coax is used as the antenna (the inner core is not used) and only the outer braid connects to output lug of the antenna tuner.
The braided rope sheath provides strength and support for the coax, UV protection from the sun, and insulation both top and bottom from the mast and deck.
The coax comes from the output lug on the tuner under the deck, through a watertight deck fitting, into the braided rope about 4 inches above the deck, up the mizzen inside the rope, out at the top about 4 inches from the pad eye, and then up to the existing insulated triatic stay between the mizzen and the main. It was simply hose clamped on to the triatic and then sealed and rubber taped.
The top of the braided rope attaches to the pad eye near the top of the mizzen. There is a loop in the rope about 4 inches above the deck and the tail passes through the deck pad eye and through this rope loop several times so that it can be cinched up to take the slack out of the line.
I have only had to tighten this up once in the last 3 years despite everyone using the line as a hand hold. The antenna appears to be just another halyard.
The length of the wire alone would probably have tuned quite well without the triatic stay, but since it was there, I used it.
This worked extremely well, and I was able to communicate with Herb Hilgenberg in Toronto, all the way across the Atlantic.
The same braided rope antenna idea could be used on any boat, on a permanent or temporary basis on the main or mizzen. The SSB rope antenna could be hoisted on a halyard or flag halyard when needed and coiled near the deck when not in use.
I will try and find a photograph to clarify this simple and effective idea.
There is a company in Florida that makes these. See
http://www.ropeantenna.com/Howard [ Just Imagine ] 19-Nov-2008
GPS (Technical)
Today it is extremely easy and inexpensive to get a GPS signal to your chartplotter or laptop. You can buy a small GPS button antenna measuring about 1" by 1" for as little as $47 that plugs straight into your USB port.
On fiberglass boats the button antenna will usually work fine below decks, as long as it is placed reasonably high up in the cabin.
On Just Imagine we have two Raymarine LP120 antennas (about $270) mounted on deck. The Seatalk version was supplied with the Raymarine radar/chartplotter that is mounted in the cockpit. The other is a NMEA version and connects to the serial port of the laptop or a serial to USB converter if no serial port is available.
You can remove the pole mount base from these small Raymarine antennas (see below)and mount them, almost flush on the cabin top or anywhere on the deck where they will not get crunched.
It is not necessary to mount GPS antennas high in the rigging. As long as they have a reasonably unobstructed view of the sky and and horizon they will work fine. The antennas are receiving up to 12 different satellites that are rising and setting and zipping across the sky all day long, and you only need to see 4 of them to get an accurate fix. I have one GPS antenna mounted on the deck, outside the cockpit coaming under the stern pushpit rail and it works fine.
These GPS antennas draw very little current, so you don't have to worry about how many you have running.
You should have at least one GPS running when you are underway. In case of emergency you need to be able to tell someone where you are and you can't wait for the unit to boot up and get a fix.
For the same reason, at anchor, you should at least write down your position if you choose to turn off the GPS.
The disadvantage of using laptops and chartplotters to show the GPS position is that they draw quite a bit of current from your batteries when you are not actually navigating. An alternative is to keep a small handheld GPS running (or a GPS with a small display) if you choose to shut down the chart plotter or laptop to save batteries when chart navigation is not needed.
Handheld units are so small and inexpensive these days ($100) and it doesn't hurt to have some redundancy on the instrument that we rely on the most.
It is true, that on any vessel the GPS reigns supreme in the instrument hierarchy.
It gives you an accurate course over the ground (COG) that is True, and needs no Magnetic correction, making your old magnetic compass reading a curiosity, rather than the essential that has been for centuries past.
It gives you an accurate Speed over the Ground (SOG) that needs no correction for currents and tides and the input from your speed log takes less importance, unless you are curious about how the currents are affecting you.
Apart from all this, it tells you exactly where you are, making sextants, RDFs and other navigation instruments a thing of the past.
The danger is that it also reduces our need to be competent navigators, and anyone who can "drive" a boat is now out on the water relying heavily on this little device to keep them on track.
One can carry several GPS units for redundancy, but this does not replace the need for basic navigation skills. Electronics can fail through water intrusion, lightening strikes, or batteries going flat and you may need to break out the hand bearing compass and paper charts when you least expect it.
Howard [ Just Imagine ] 10-Mar-2008
USB to Serial Converter (Technical)
It is hard to buy a laptop today with a 9 pin serial (COM) port as most of the new models only come with USB (Universal Serial Bus) ports.
The USB to serial converters have improved over the last few years and are now mostly quite reliable for GPS and other applications.
On Just Imagine we use inexpensive ($30) Keyspan USB to Serial converters that are readily available and so far have had good results. There are several other choices and prices available.
The GPS NMEA cable connects to pins 2 and 5 of the 9 pin connector. Look for the tiny numbers (1-9) on the connector.
Pin 5 is the ground connection and pin 2 is the NMEA signal coming from the GPS.
If your laptop software can upload waypoints to the GPS device, then you need to connect pin 3 as well, which is the NMEA signal from the laptop to the GPS.
Howard [ Just Imagine ] 10-Mar-2008
AIS receivers and Transponders (Technical)
AIS receivers are still a bit expensive but hopefully they will come down in price with popularity.
An AIS receiver receives signals from commercial ships that are required to carry AIS transpnders. The ships continuously transmit ship's name, call sign, vessel type, speed, heading, course, position, navigational status and MMSI number for DSC calling.
The receiver outputs NMEA -0183 to your chartplotter or radar(if compatible) and will be displayed on the screen with the ships information. This allows you to see, graphically the direction and course of the ship and enables you to call the ship by name on the VHF, or even directly, using a DSC VHF.
The AIS receiver operates at VHF frequencies 161.975 (Marine ch 87) and 162.025 (ch 88) MHz (9600 bps GMSK 25 or 12.5 kHz HDLC). Unfortunately, the audio signal one gets from a normal VHF cannot be used for AIS data. Apparently certain model Icom VHFs can be modified for this purpose, Hopefully, one day AIS will be incorporated into all our standard VHF radios.
The deluxe version is an AIS transponder, that will not only receive the information, but also transmit your vessels information to other ships in your vicinity.
Howard [ Just Imagine ] 13-Mar-2008http://www.waypoints.com/ais.html
www.milltechmarine.com
Smart Radio SR161 $189
Conflicting opinions about Nasa/Sitex low cost AIS receiver
Comparison $200-$600 from MilltechHoward [ Just Imagine ] 13-Mar-2008
Iridium (Technical)
Iridium is quite a handy alternative for cruisers.
This system works on a network of many low earth orbit satellites rotating around the Earth, just a few hundred miles up, as opposed to 22,300 miles for fixed satellites. The closeness of the satellites allows for small, low power handheld terminals.
The satellites are moving all the time, rising and setting and zipping across the sky, and you can usually 'see' more than one at a time.
During a conversation, you may be handed off from one setting satellite to another, as they rise and set. In the early days, your call would sometimes be dropped during the hand off, but it was still a worthwhile service if you could tolerate a few dropped calls. I have not had recent experience, but hope that this has been improved.
The handheld terminal costs about $1300 and then you pay about $1/minute for voice calls. You normally have to buy $500 worth of minutes up front which, I believe, expire after 1 year.
You can also hook a laptop to the phone and do slow speed data (8Kbps) and email, but it is certainly not suitable for browsing the web.
One advantage of the portable Iridium phone is that you can take it with you when you go ashore and you could even take it with you in a life raft if needed.
It is really handy when you enter a new country and your old GSM prepaid SIM card does not provide coverage.
Howard [ Just Imagine ] 01-Aug-2008
Fleet Broadband 250 (Technical)
Fleet Broadband is the latest from Inmarsat, combining simultaneous voice and Internet access in the same terminal. The FB250 is capable of data rates up to 280Kbps and the FB500 up to 432kbps.
The FB250 terminal is housed in a 12" radome and can easily be mounted on a mizzen mast bracket or on a pole on the transom.
It can be quite costly for a cruiser budget. The terminal costs about $12,000 and then voice calls are about $1.50 per minute, and data throughput is billed at about $16/MB.
The data connection is "always on" and you are only billed for the bits, or megabits that you use.
I believe there is also a monthly access charge of about $100.
If you are a really heavy data user (and extremely wealthy too) you can get the data rate cost down by purchasing bulk plans in the region of $3,300 worth of minutes per month with a 12 month minimum, but I think this is the wrong audience for that.
Right now, in July 2008 the service only covers the Atlantic and Indian Ocean regions, but the Pacific will soon be included.
FB250
Voice - 4 kbit/s or 3,1 kHz Audio
Fax - Group3 fax via 3,1 kHz Audio
SMS - Standard 3G up to 160 characters
Data Standard IP - up to 284 kbit/s
Streaming IP 32, 64, 128 kbit/s
Antenna - diametre from 25 cm, weight approx 5 kg
FB500
Voice - 4 kbit/s or 3,1 kHz Audio
Fax - Group3 fax via 3,1 kHz Audio
SMS - Standard 3G up to 160 characters
Data Standard IP - up to 432 kbit/s
Streaming IP 32, 64, 128 256 kbit/s
ISDN 64 kbit/s
Antenna - diametre from 57 cm, weight approx 18 kg
Howard [ Just Imagine ] 01-Aug-2008