The Antenna is ImprovedFrom my day of testing, I've determined that the iPhone 4 performs much better than the 3GS in situations where signal is very low, at -113 dBm (1 bar). Previously, dropping this low all but guaranteed that calls would drop, fail to be placed, and data would no longer be transacted at all. I can honestly say that I've never held onto so many calls and data simultaneously on 1 bar at -113 dBm as I have with the iPhone 4, so it's readily apparent that the new baseband hardware is much more sensitive compared to what was in the 3GS. The difference is that reception is massively better on the iPhone 4 in actual use.
Most of the antenna problem is actually mitigated in the CDMA iPhone 4. How? Antenna diversity.Antenna diversity can be implemented a few different ways. You can switch between two different antennas quickly depending on which is experiencing temporary fade (from a hand touching it), or you can do some averaging and hope that even with significant fade on one antenna, there's still enough signal to keep you above cutoff. It's not clear what Apple has implemented on the CDMA iPhone 4, but as we'll show later, it definitely mitigates the problem in most cases. Diversity won't magically give you better signal strength (nor will it save you if you cover both), but it will help keep SNR and overall link quality high. The MDM6600 has full CDMA and WCDMA RF receive diversity support with the inclusion of an external switch. It's not entirely certain what part is the switch, but it's definitely there.How else do we know that the CDMA iPhone 4 has diversity? It's part of Verizon's own specifications for what devices need to have to attach to their network. Buried in the required open alliance spec datasheets is the following:There we have it, if you want a device approved for Verizon's EVDO network, you need receive diversity.