Tuesday, 27 May 2014

Magellan FX324 Map GPS receiver info

About the antenna…

When we bought Spray, she was equipped with a now-obsolete Magellan FX324 Map GPS receiver.  The signal was very feeble and an electrician told us the antenna was dead.  We ordered a new antenna (about $150) and were told we were lucky to get one because they weren’t making them anymore.

It worked well for about 1.5 years and then we started having problems again.   The time to first fix could be anywhere from 15 minutes to 4 hours.  We moved the antenna around to different locations and repaired frayed wires, but results were very sporadic ;  good for a couple of weeks and then out again. 

A different electrician had a look at our GPS this morning and, like the first, deduced a problem with the antenna.  After my ear-piercing squeals of protest, he gently explained to us that the Magellan FX324 has a built-in antenna and that  ** YOU DO NOT NEED AN EXTERNAL ANTENNA IN A FIBERGLASS BOAT.**  The external antenna is only needed for metal boats (aluminum, steel, etc.).  The Magellan documentation does mention the presence of an internal antenna but they insist you must have an external antenna (Magellan brand, of course) if the GPS receiver is located inside the boat.  To test this, we simply disconnected the antenna from the back of the GPS, which resulted in a strong first fix in less than 2 minutes.  With the antenna cable attached this morning, it took more than 4 hours.  

We will keep the antenna cable ready to connect in case this strange new method ceases to work for some reason.  I’ve now tested our external antenna-less GPS several times throughout the day, trying to sneak up on it or catch it unawares, but it gives a strong fix, every time.  Bewildered relief.

About the power / data cable…

A blog reader contacted me several months ago to ask if I had any documentation for the data / power cable pins of the Magellan.  I looked through the user’s manual but didn’t find anything.  I tried searching the web for this information in both French and English.  Not only did I not find the information, I found several forums where others were asking the same question.  I asked our electrician if he had a pin-out and he promptly directed me back to my user’s manual, where the information was hiding all along.  I was looking for a circular diagram of the cable pins and the information is listed as a simple table.  Sorry for the delay.

Without further ado, here it is:

FX324 MAP Description                               FX324 MAP Wires
Power 10/36 volts                                          Red
Power 0 volt                                                     Blue
RS232 Reference                                            Green
RS232 Input                                                      Black
RS232 Output                                                   White
RS422 Reference                                            Orange
RS244 Output                                                   Yellow