I remember doing my IMC training and struggling hard to get my head around VORs and NDBs and how to interpret the instruments to figure out where I was in relation to them. I used a program called RANT to try to figure it out and it help a bit. Now there’s an app for it – Radionav Sim – written by a friend of mine, Vincent Lambercy. It’s pretty cool and much cheaper than RANT. Well worth getting if you’re studying for an IMC or IR or just trying to learn radio navigation.