GSM/EDGE vs 3G Band Settings Call Drops Experience

[Camp]

I want to know why this happens. I already have a solution but I am more interested in the specifics of what is causing this. Keep in mind that this does not happen everywhere, but only at my home/vicinity (general square area/radius of about 1 mile)

This is the problem:
When my phone is set to AUTO in terms of band settings for data/voice, I experience a massive amount of dropped calls. I can barely hold a conversation because my call will drop every 2-7 minutes and it is very embarrassing when trying to conduct business.

Solution:
The solution I have found is to manually set the phone to force either GSM/EDGE or 3G, but not both. When I do this, my problem is solved 100%

SPECS:
Network: AT&T
Phones Tested: AT&T Tilt and AT&T Treo 750

[NiteStalker]

I have this problem in areas where they haven't completed the upgrade to 3G yet. I suspect it drops because the compatability between 3G and Edge is none, the phone has to switch to different bandwidths that cause a quick but temporary loss of service, effectively dropping your calls.

I have seen an app that forces data connections to stay off, using this app in areas where it swtches between services might improve your issue.