Last Friday we told you we were putting Griffin’s contentious ClearBoost iPhone Case through its paces: Griffin’s sales claim is that the ClearBoost’s in-built copper antenna strip is enough to give you an extra bar or two of coverage when using AT&T’s network.  Since then, iPhone Buzz has been hauling the case around various areas of great, middling and patchy coverage, trying to work out whether the $29.99 Griffin are asking is a steal or just daylight robbery.

As was to be expected, it’s not a black & white outcome.  Using the ClearBoost case – and monitoring the iPhone’s signal strength via the Field Test software rather than the less-than-accurate bars display – in some situations saw much increased reception, while in others the case actively reduced reception.  At its best, the case significantly improved the iPhone’s reception; considering 3dBm difference actually means the amount of RF energy reaching the iPhone’s antenna doubles, we observed more than four times the signal using the case in each area.  As Griffin point out, that could make the difference between a failed and a completed call, although whether the iPhone displayed a difference in bars (as opposed to the Field Test app) varied.  

However, when we used the iPhone with a Bluetooth headset (e.g. with the handset itself on a desk or table, or in a bag) the benefits of the case disappeared; in fact, while the ClearBoost did not affect the iPhone’s reception in strong signal areas, having the case actually hindered the cellphone’s reception in medium and weak signal areas.  Ironically, the case reduced reception in the weak signal area by almost the same factor as it improved it when the iPhone was held rather than used with a headset. 

The difference could be due to the position of the iPhone antenna, at the base of the handset, which is blocked by a users hand when held normally but not when the handset is used hands-free.  Griffin themselves suggest that it’s the copper strip inside the case (terminating in the stub at the top) which “repositions” the iPhone antenna to remove that obsticle.  We looked at signal strength when the iPhone was in a metal case and observed similar reduction in signal strength whether the handset was held or set down.

As a case, the ClearBoost seemed as sturdy as any other polycarbonate example we’ve seen, and the screen protector is a nice touch.  Although it fits the iPhone snugly, it would be nice to see some cushion material lining the inside to guard against scratches.  Obviously, the stub aerial is a varying annoyance depending on where you keep your iPhone: upright in a pocket it actually gives something handy to grab onto, but horizontally it can catch on fabric and be a minor struggle.  Aesthetically, like many hard cases, it’s not exactly a prize-winning beauty.

Is it worth $29.99?  That depends on how and where you use your iPhone: if you usually rely on a Bluetooth hands-free, or live in an area with generally decent AT&T coverage, you’ll either notice little improvement or, in some cases, worse performance from your handset.  If you hold your iPhone normally, and have issues with poor quality, glitchy calls or dropped connections, the ClearBoost could improve your experience.

iPhone Buzz tested the ClearBoost case taking multiple readings from the Field Test app on an non-hacked iPhone using AT&T’s network.  Figures are an average of those readings.  If you buy a ClearBoost yourself, we’d be interested to hear your experience with the case: let us know in the comments or via the tips page.