Apple's iPhone 5.

Apple's iPhone 5.

LTE offers blistering speeds for iPhone 5 owners, but results are far from consistent.

Now that I've got my hands on an iPhone 5 from Telstra, Optus and Vodafone, I decided it was time to take them all for a spin around Melbourne to see what kinds of speeds I could squeeze out of them. This is obviously not a full review of the iPhone 5, just a closer look at some interesting features. Earlier this week I looked at the new screen and the improved camera.

Having tested out a few Long Term Evolution (LTE) gadgets on Telstra's Next G network earlier this year, I knew the results would be hit and miss. Your speeds really depend on where you are, what time of day it is, who else is around and the location of your nearby towers. There also seems to be a certain element of luck involved. To be fair that's the very nature of wireless technologies and certainly not limited to LTE.

The Vodafone handset was obviously at a disadvantage, because only Telstra and Optus have launched their LTE networks. Vodafone isn't expected to publicly offer LTE until next year, but its recent upgrade to 3G+ in the inner cities is clearly paying off. Standing in the Melbourne CBD at around 8pm I managed to pull down an impressive 17 Mbps on Vodafone. Telstra couldn't manage any better and Optus could only hit 25 Mbps, even though I was connected to their LTE networks.

Of course at that time of evening during the week you don't expect too much congestion on the CBD mobile networks. You've got much less chance of pulling down those speeds once there are a more people wandering around, and once more people have LTE devices. Don't expect those kinds of speeds on your lunch hour, especially now the iPhone 5 has come to the party and spoiled it for the early LTE adopters.

Heading away from the city towards Tullamarine Airport saw results vary. Optus has a wider LTE footprint than Telstra at the moment, but Telstra customers fall back to Dual-Cell HSDPA for a while before they're relegated to HSPA+. The iPhone 4S introduced HSPA+ support, so if you're still using an iPhone 4 you'll feel a speed difference on the 4S/5 even in HSDPA areas. 

Sitting on Flemington Road alongside Royal park, maybe two kilometres from the CBD, Vodafone was back to a disappointing 5 Mbps while Telstra and Optus both hit 22 Mbps. Then Optus dropped to 11 Mbps. Then back 22 Mbps again. Like I said, far from consistent. In that very spot five months ago, at roughly the same time of evening, I clocked a phenomenal 55 Mbps using Samsung's Galaxy Tab 8.9 4G on Telstra's LTE network.

From here I headed down the Tullamarine Freeway to the airport, because it was one of the early Telstra LTE patches beyond the CBD. Sitting just outside the airport near the business park I watched the iPhone 5 tear Telstra's Next G a new one -- pulling down 56.65 Mbps with 21.90 Mbps up and impressive 39ms ping time. Meanwhile the Optus iPhone 5 was pulling down a not-too-shabby 24 Mbps on LTE, while Vodafone could barely muster 4 Mbps on HSDPA. In the same spot five months ago, same time of evening, I could only squeeze 27 Mbps out of the Galaxy Tab 8.9 4G. Like I said, very hit and miss.

So what can we learn from this? LTE is fast, lightning fast, when conditions are right and the gods of mobile broadband smile upon you. But if you dream of pulling down 55 Mbps all day, everyday, you're in for some major disappointment. Telstra customers have the advantage of Dual-Cell HSDPA once they stray beyond LTE coverage, but right now Optus' LTE coverage extends well into Telstra's Dual-Cell HSDPA footprint. So in some areas Optus is much faster than Telstra. But from my experience once you get further into the burbs, or beyond the city, you'll generally get better and more reliable performance from Telstra. 

Optus and Vodafone have an uphill battle to win back customers after they let their network performance deteriorate so far and it will be interesting to see how their LTE offerings cope once they're under heavy load.

Telstra brings something else to the party in the form of HD Voice, using Wideband Adaptive Multi-Rate coding (WB-AMR) which is a wider audio frequency. In other words, your voice should sound richer and more natural. It's enabled across the entire Next G network and is compatible with a handful of handsets such as the iPhone 5 and Samsung Galaxy S III.

Unfortunately the HD Voice quality between two Telstra iPhone 5s isn't all I hoped for. Voices are richer but can they also have a touch of reverb and the slightest of echos, as if the person on the other end was sitting on the toilet. Some calls are worse than others. Voices might be clear but they're very harsh and distorted like a clipped audio file. It's very annoying to listen to but unfortunately there's no way for Telstra customers to disable it when calling other Telstra customers.

Switching to speakerphone sounded better, suggesting the issue might be with the iPhone 5's three microphones and/or voice processing rather than Telstra's network. Unfortunately Voice HD calls to two iPhone 5s, a Samsung Galaxy S III and a Nokia Lumia 800 (thanks @WP_DownUnder) didn't sound much better on either end. 

I rang my colleague Jen Dudley-Nicholson in Brisbane, a tech reviewer who is using an iPhone 5, and she said it was the worst HD Voice call she'd heard -- like a disappointing VoIP call. I rang her back from a Samsung Galaxy S III and she said it sounded just as bad, like I was in a tunnel, although she didn't sound as harsh to me. I'm starting to think it might be a Telstra network issue. It's not just my cell tower. I got another Melbourne friend with an iPhone 5 to ring Jen and it was just as bad -- Jen sounded like she was on a dodgy VoIP call and my friend sounded like she was in a tunnel. Clearly something isn't right. Voice HD is supposedly enabled across all of the Next G network, but perhaps some patches are worse than others. Perhaps it's a Melbourne issue.

It seems that your mileage may vary when it comes to Telstra's HD Voice, but most people seem happy with it so hopefully it will sort itself out. Until then it would be handy if you could disable it.