I have bought a Plastimo Mini C Compass to go in my Osprey, I am having to mount it on an angle which it is designed to do. Problem is my VHF radio will be directly below the compass on the console and there will only be a few inches between them.
Does anyone know how large an affect the Icom 421 will have on the compass. Is it only whilst transmitting?
As you probably know from the documents with the compass, the recommended fitting distance is a metre away from the radio. I suspect the biggest impact is the magnet in the speaker for the radio. When the radio is alive (receiving or transmitting) there will also be a lot of EMI about from speaker itself and also radio transmitter. This will be shielded somewhat by the metal box the radio is mounted in.
I reccon my compass is 40-50cm away from radio body and it doesn't seem to affect it. You should be able to judge the impact just by placing the compass in situ and see if it deviates any from it being in another location away from the radio. I suspect you will however see an effect with the radio so close.
Remember the mike also has a magnet in it although I didn't notive a huge effect with the mike (it's quote close to my compass).
Not noticed any effects on my compass and I have the 421 only about 50 cm away. It certainly doesn't effect it normally. I haven't observed the compass whilst using the radio though to see if it affects it.
By the way I should imagine that a compass on a RIB is always going to be a compromise. Its never going to be 100 % accurate. Unless that is someone has gone to the trouble of calibrating it properly and working out any deviation factors. I also carry a handheld compass as backup but generally just rely on the GPS. Might be a bad idea I know but it is the 21st century and I do know how to use a compass if needs be.