Saturday, May 4, 2013

A Few Nuts and Bolts of Iridium SatPhone Usage

With an Iridium satphone you can make voice calls, send email, and receive weather data from anywhere in the world.  Turn it on, pull out the antenna, and rotate it so it will be in the vertical position when talking, get a clear view of the sky so you see bars showing (just as with a cell phone) and dial the call: 001, area code, number.  001 is for calls from ship to US. Other calls take different prefix. Or select a stored number and press call. The handsets work just like a cell phone and they are not a lot bigger.

Once connected the communications are excellent. Better than many cellphones, and almost always better than using the HF radio. Calls are charged at anywhere between $1/min and $2/min, depending on the provider and package purchased. Generally the more time you buy, the better the price, but the plans all have time limits (ie 200 min or 1 month, whatever comes first), so this must be taken into account. Billing is done in 20-sec intervals. You can turn on a timer that will beep every minute to remind you of the time. It generally takes 40 sec to do anything. There are also counters in the phone and webpages that list all of your usage.

A very nice feature of the Iridium program is the ability of users on land to send short (160 characters) messages to the phone at no charge to sender or receiver. There is a limit of 150 messages per month, so you have to monitor the use of this feature. You can set up a personal shorthand code to convey standard messages and make a list of standard abbreviations.  See 

The phone has a standby time of up to 30 hours and a talk time of up to 3 hours. There are two chargers, an AC adapter and a cigarette lighter DC adapter. It takes about 2 hours to charge the phone.

The popular Model 9555 phone is not the latest model from Iridium, but the one just before latest, which is for now the one often used in rental programs. Sat phones rend for about $200 per month from several sources around the country. In times of major disasters like Katrina, it could be very difficult to rent or even buy a phone anywhere in the country. The phones cost about $1200.

Here is one airtime price list from May, 2013

PrePaid Air Time Duration Price Price per min
75 minutes 30 days $160 $2.13/min.
225 minutes 180 days $450 $2.00/min
500 minutes 365 days $750 $1.50/min
750 minutes 180 days $750 $1.00/min
1,000 minutes 365 days $1,400 $1.40/min
3,000 minutes 2 years $2,800 $0.93/min
5,000 minutes 2 years $4,000 $0.80/min

Here is another

PrePaid Air TimeDuration Price Price per min
75 30 days $150 $2.00
150 60 days $295 $1.97
200 6 months $500 $2.50
500 12 months $795 $1.59
1000 24 months $1,490 $1.49
3000 24 months $3,209 $1.07
5000 24 months $4,499 $0.90

For voice communications, the connection continuity is not super critical. You might even talk well with just a couple bars. BUT this is not at all the case with data transfer, such as email and file transfers. Voice is more tolerant than data because humans can understand a dropped syllable or two in conversation, but data transfers cannot.

Data transfer requires strong signal
For data transfer with the sat phone we must have a full strength connection, all five bars showing, and steady for at least 30 seconds or so, before even trying to connect.  If you try to connect without this check, you will lose contact intermittently and the connection to the server will be lost. This connection (hand shake it is called) can take about 30 seconds or more.  The problem is if the connection times out, it shuts off and you get nothing except an air time charge for 40 seconds. There is an option in the software for setting the time out time if this is marginal.  The best bet is be sure the signal is good and steady before trying.

This point cannot be overstressed. If you try to get data with less than perfect connection you might get part of it or nearly all of it and then lose the connection and thus you get nothing except the bill for the air time.  Air time is charged no matter the success of the call. This is even true in commercial services that offer direct requests for weather files.  Don't even ask for data unless you have very good connections that you have monitored for a couple minutes.

Another way to check and monitor connectivity is a satellite signal strength software module installed called SatMon. This can improve knowledge of signal strength over just looking at the phone. SatMon samples the phone every 3 seconds for strength. The phone display can take up to 10 seconds to report the signal strength.  If the time it takes to report back signal is long then the SatMon will timeout and display 0. So you get bouncing bars on SatMon if the phone is not reporting right away.  This usually means you have doubtful connections.  You really need 5 bars of unwavering signal on the phone display before you attempt to connect. If you don't,  you will have a timeout and a bad connection.  I have tested cases here with a solid 4 bars showing on the phone, but yet SatMon kept bouncing to zero periodically, and I could not connect. Unless you know 5 bars is full signal, you could conclude from just looking at the phone that 4 bars is full signal!

And that is not the full story.  The bars and monitors are monitoring the incoming signal strength. For data transfer you need good clean connections in both directions. At sea in open water, the full bars will mean you are good to go, but in near-coastal waters, especially in a harbor you may have interference on the transmit side even though you have full bars on reception. Near any large ships or working docks where there might be welding or a lot of TVs or other radio interference it might be that you cannot make good data connections even with 5 bars of reception strength. We have heard of cases where mariners had to take their phone off the boat and go some distance away from the marina to get good data transfer.

There are also satellite position monitoring apps for smart phones that might help you anticipate best times to call. I have not tested them for this app but we use them all the time for predicting weather satellite passes.

Another important point is to be sure the connections are all snug. A loose connection will also interrupt the signal and cause a drop. If needed, put a rubber band around the connector to hold it into the phone tightly. If you are moving about the cabin with the cable stretched out it can pull this loose.

For data connections, the computer is connected to the phone with a mini to normal USB cable. This cable can be up to 10 ft long. You can also use extensions, one 3 ft and and extension of about 6 ft.

Which brings up an important detail of data transfer. When you install the drivers in the PC that link the phone to the PC software, it associates a specific USB plug on the computer with a com port, and that com port is then registered with the software. Thus you must always be sure to plug the phone into the same USB port you used when registering the device.

So if there is any chance that this could be confused (maybe more than one user) then tape a note on the computer of where it goes.

If the cable is not plugged into the right port you will get error msg 633 or 634, but it does not say wrong port. You will get the same error msg if you end up with an unconnected plug. It could just say you are not configured properly, or something like that.
When installing the drivers for the satphone, you must use a com port number between 3 and 9. If there is any doubt about the ports on a PC computer, you can go to Device Manager and then Ports and watch the list to see what the number is as you unplug and replug the device. (On Win 7 just go to Start button and type in device manager. )  Your sat phone email software will have a Properties link somewhere that tells you what com port it is looking for. (I will have to add later the related notes for a Mac).

We can hope that the phone would work inside the cabin and not be influenced by the fiberglass overhead. But this has to be tested, and not counted on. If you might be located below a bank of solar panels on the deck, this might not work. Also your access to the full horizon is always compromised below decks. Thus a proper external antenna for the unit is valuable if you plan to do much data transfer.

You can get by without that, but it is a tremendous convenience. I sailed with these multiple times without the antenna, but then you have to then leave the phone on the deck, with the cable leading to the computer below decks, and so more nuts and bolts. If it is raining or rough conditions, one has the challenge of keeping it dry. The phone can be put into a well sealed plastic bag and used outdoors in the rain. I have done this  numerous times, but not proud of it. But for data transfer we need the cable to the PC, and if conditions are rough we also have to have the cabin secured.

The advantage of being in the middle of the ocean (as opposed to at home with buildings and hills around) is you do have a full horizon to see satellites. There are 66 satellites in low earth polar orbit, which means each circles the earth in about 100 minutes (same as ASCAT-Metop-A, which is at 104 min).  There are six orbital planes spaced 30 degrees apart with 11 satellites in each. So there are always some available, but crossing the tropics, the density of useable satellites is lower than at higher latitudes. It should not be a problem any time when standing in the cockpit, but there could be some timing issue if there is just one location in the cabin that works,  i.e. over against one side of cabin, with a slice of sky not blocked by solar panels overhead.

Thus this is not just a one time trial to learn the potential of inside use.  It must be tried several times during the day to rule it out or find it works under special conditions.  It could be that just turning on the phone and the SatMon program when working on the computer for other purposes they might be able to detect useable times.

Another important note is you cannot use the "hockey puck" external antenna that comes with every unit in the box. These have a magnet connector and are actually intended for car-top use on land. I am not sure of the science, but i believe they count on the metal car roof for a ground plane to work efficiently. In any event, it is well known that they are not very effective on a boat.

As for data transfer efficiency, we have to accept that the transfer rate is not high. Nothing like we are used to on our wifi connections. Sending one short email takes about 40 seconds, but a list of 5 very long mails, even to multiple addresses takes only about 50 sec. The best approach is to use a batch and send procedure. That is write emails throughout the day, but only log on once a day to download your incoming mail, send outgoing mail, and receive your weather data all in one connection. this saves the unavoidable connection costs of individual logins.

Weather data via sat phone will be mostly be in text or GRIB format, and for the latter my rough estimates are 3 days of wind data over a 10º x 10º grid will take up 10 kb. This would be the same for waves or precip or pressure. You can scale that to anticipate the file sizes. But all of the data is stored so you can after downloads look at the data file to see actual file sizes. Using sat phones for weather data is discussed in Weather by Satellite Phone.

To send emails for communications or weather data, you will need special software for your  computer and  an account with a provider of these services. Some also offer the option of tagging each email with your position, COG, and SOG if you have a GPS connected to the same computer.

A final but important note for small craft mariners. These phones and their connectivity are super convenient, despite the fairly high price of communications. So much so, that they can be taken for granted after much use. This is a mistake.

If the unit did not come with it, I would recommend getting a water proof, crush proof Pelican or Otterbox case for the device and its charger (any that it fits it will do).  Then make it an absolute rule that it always goes back in that box, and the box gets sealed when done. (This applies to hand held units not incorporated into the nav station with a docking unit.)  Otherwise, it is easy to mix them up with a cell phone, and just set it aside when done, without its full protection. Then if some water gets into the boat –– either big time or small –– it can damage one of your important links to land and other vessels.

No comments:

Post a Comment