crap crap crappety crap.
I just did some tests on this remote interference. Can't believe I haven't noticed it before. I just wrote the noise off to mic shortcomings...how wrong I was.
As Mmmm suggested, I set source to line in, didn't plug a mic in, then recorded w/ a varety of gain, then measured noise floor (in dB):
First with no gain (left channel, right channel):
w/ remote: -84, -81
w/o rem: -84, -84
w/ remote: -72, -63
w/o rem: -81, -81
w/ remote: -42, -36
w/o rem: -52, -52
I repeat: crap crap crappety crap.
LinusN suggested that the main iriver units aren't grounded properly...some worse than others. I think this idenitifies the damn source of cell phone interference I've encountered in some of my recordings. Unless I'm mistaken (and that's entirely possible) the remote is essentially acting like a giant antenna.
So, now all we need is an electronics guru to confirm this issue and find a fix (please!).
edit: oh, and 'reduce ticking' makes no obvious impact on the interference.