I've had four N4s, all have had the problem equally. I'd say it's a shielding issue that is a fault by design that is causing the problem. It doesn't really bother me as it isn't that noticeable during day-to-day phone calls, only really hear it clearly when on the phone at home where everything is silent.
As for custom kernels, I personally don't bother. I've not seen any evidence that the tweaks make a huge difference to battery life. People claim to see a difference, however battery meters reading incorrectly (and thus shutting the phone off before the battery is truly depleted) and different types of usage will count for the differences. I'm getting similar battery life to those claims with the stock kernel anyway. The performance sacrifice is annoying as well - installing franco's kernel lead to jittery scrolling everywhere (I know why), and I really cannot be bothered to faff about under the hood to sort it. Why should I why when the stock kernel works perfectly from the get-go?
Psycho Sonny, care to elaborate on your usage? Sounds like something is going on in the background that is causing it to plummet.
As for custom kernels, I personally don't bother. I've not seen any evidence that the tweaks make a huge difference to battery life. People claim to see a difference, however battery meters reading incorrectly (and thus shutting the phone off before the battery is truly depleted) and different types of usage will count for the differences. I'm getting similar battery life to those claims with the stock kernel anyway. The performance sacrifice is annoying as well - installing franco's kernel lead to jittery scrolling everywhere (I know why), and I really cannot be bothered to faff about under the hood to sort it. Why should I why when the stock kernel works perfectly from the get-go?
Psycho Sonny, care to elaborate on your usage? Sounds like something is going on in the background that is causing it to plummet.