Definitely batteries too. It's one of the worst possible offenders because it's hooked directly to the ignition module, which is probably the main source of interferance.
If you just move the battery up a little and the rx battery back a little, you're not helping anything because the ignition battery will still be in close proximity to servo leads, the antenna, rx switch and that type of thing.
The rule of thumb is to keep everything that's directly connected to the ignition at least a foot away from everything that's connected to the reciever. That means everything...batteries, switches...everything.
No sense in using a nyrod for throttle servo, separating your reciever from the ignition module and all of that if you're going to take the ignition battery and place in next to reciever battery.

Now, as a disclaimer...People have broken all of these rules from time to time and gotten away with it but as a general rule of thumb, these are the rules.

BTW, the ferrite rings are a good idea but not a substitute for separation in my opinion. You generally place them as close to the receiver as possible.