Late, but here's my $.02. Everything they said above about checking connections plus be sure the antenna is mechanically solid, not wiggling around, and that it has a good ground. If it's only happening when the engine is running, the ignition or alternator could be causing it.
We could help more with more info. When does it happen?
Engine stopped, sitting still: connections and grounds
engine running, bike still: alternator or ignition
bike moving: bad connections
at home or everywhere? If only at home, the source is something outside the bike.
Is it constant crackle or random? Random when moving is very likely a bad connection. Constant when running might be ignition.
whine that varies with engine speed or unrelated to it? Whine that varies with engine rpm is alternator.
There are filters you can put int he line from the alternator to cut whine. Anyplace that sells car audio has them, maybe Radio Shack still does if they haven't taken them out to make room for cellphones. I miss the old Shack.
When you are checking connections, they can look ok but not be. It doesn't take much corrosion to cause trouble- a literally microscopic layer can be enough. Clean them as best you can. The tabs and pins in connectors are pain but I've found soaking the whole thing in white vinegar for a while does wonders. It's harmless to wires and paint and it's cheap. Put some on a sandwich bag or small cup and get the connector into it for a half hour to hour if it looks really bad. You'll see the crud in the vinegar. You can rinse with a bit of water but if you do blow dry immediately. Better to just shake it out and let it air dry before the next step:dielectric grease.
I am a HUGE fan of dielectric grease. You can get it at any auto parts store in tiny packets for small jobs or big tubes. Before you put that nice clean connector back together fill it with the grease. It keeps out moisture, even damp air. I promise in 5 years it will still look like it does now. I put it on every electrical connection of every vehicle I have and even outdoor light bulb bases on the house. I even put a dab on the terminal of the spark plugs. I have no corrosion or stuck bulbs. I only have to do it once per socket, it stays so a replacement can go in dry. Get some!