Saturday, May 31, 2008

Two-meter radio instead of cell phone

A recent search term that brought someone to my blog was "2m radio instead of cell phone". I touched on this topic somewhat in a previous post. However, I didn't talk about particular topic in much detail. There's a whole bunch of differences between using a two-meter handheld for personal communications, and using a cell phone for personal communications.

First, let's ignore the presence of infrastructure. In the absence of infrastructure, the two-meter HT is a lot more useful, but only because the cellphone is just about useless. The only way I could communicate with my cell phone in the absence of service (other than throwing it like a rock) would be to use its flashlight to send messages in Morse code. The HT, on the other hand, will be useful even in the absence of any infrastructure to communicate with someone else (within a relatively small distance) who also has a two-meter HT, in what is known as "simplex mode". So in the no-infrastructure case, the HT wins easily.

But that all changes once you bring infrastructure in. The "ordinary" infrastructure that one would have access to with a HT would be a two-meter FM repeater. There's a lot of these out there, although there's no coordinated way to find out other than looking up your location in a database. Most notably, the HT won't find one on its own; the operator will have to know from a third party database what frequency and squelch tone are required to access the repeater. Also, the person you want to talk to will also have to be listening to that repeater (and not some other repeater), which means they'll have to be somewhere within that same repeater's geographic coverage area, typically a range of 30 to 50 miles. On the other hand, the cell phone allows you to talk to anyone with a phone (cell phone or not) anywhere in the world, knowing only their phone number. Neither you nor they need to know which cell tower you're using. The network takes care of all of this. There are technologies that exist in ham radio that bring the 2m HT closer to the cell phone, things like autopatches and repeater linking, but autopatches are increasingly less common (mainly due to cell phones) and repeater linking not widespread enough to come close to the capabilities of the commercial cell phone networks.

In addition to the above, there are several other major differences. The cellphone is private (encrypted with newer standards), full-duplex (both sides can talk simultaneously), and exclusive (you do not share your channel with anyone else). None of these is true of the amateur HT. All communications on a HT (whether simplex or through a repeater) are over public, unencrypted channels as encryption is forbidden (with only two exceptions) in the amateur service. Typical amateur handhelds are half-duplex only, which means you can either talk, or listen, but not both at the same time. There is no practical way to do full-duplex within a single band; the filtering required would be technologically challenging to put into a handheld device. Finally, you will be sharing the frequency and the repeater with whoever else might be using it.

In short, the 2m HT is no substitute for a cell phone in ordinary circumstances. There's only two ways in which the HT is superior: it works, at least somewhat, even when you don't have an available cell network, and you don't have to pay for a service contract in order to use it. It's the former that makes the HT extremely valuable when you're off in a remote area or during a communications emergency.

The main value of having all these hams with handhelds out there is so that when there is a disaster, there will be people out there with the equipment and the experience needed to effectively provide emergency communications. Otherwise, it's pretty much just fooling around with radios. Which, to be fair, is a great deal of what hams do.