I have seen that my JASJAR is sporadically sending/receiving data in the background even if the applications are apparently inactive. This is causing the radio connection to stay up for a long time. Especially on Vodafone Spain UMTS network radio connections are kept for ~20seconds after the user data is sent.
The only application I had running was ActiveSync, with an update period of 5 minutes. However, within the 5 minutes I can see activity in the channel every 40 seconds approximately, even when ActiveSync has finished synching.
Anyone knows of any good packet sniffer for WM5.0 to identify exactly what that traffic is for?
As a consequence of what I think is background ActiveSync traffic, radio transmission is performed for a considerable amount of time (radio channel is active 33% of the time in my case), which drains battery extremely quickly.
This is related to this specific network implementation (all data sent on CELL_DCH mode, for those who understand UMTS RRM, though this is very likely to change in the near future), while other operators are using CELL_FACH, more similar to GPRS behaviour and more efficient in terms of battery usage. What network operator are you using?
If you want to avoid the UMTS network in order to maximise battery you can force the phone into GPRS only mode in Settings-->Phone-->Band and changing from Automatic to GSM... at the cost of not having video-calls, simultaneous voice+data or high download speeds.