Communication Technology

Mostly New Diasporia is an RPG background that is game system agnostic. Since I use GURPS, particularly GURPS 3rd Edition, with some GURPS 4th edition rules, I from time to time talk about game system specific rules, particularly design rules.
Today I'm going to talk about communication rules in GURPS. I'm going to start out by saying the rules are broken. Why do I say that? Because today at TL8 we have communication devices which exceed the capabilities of the higher TL devices listed in UltraTech (both G3 and G4).
As a general set of rules they're workable enough for someone who doesn't have a background in electronics or communication systems. Unfortunately I do. They also break down when compared to existing devices.
Let's lay out an example. The typical cell phone weighs in at about .28 lbs. That includes it's battery and no less than five different radios, operating on different radio bands. They include a GPS receiver, a cell duplex channel radio, a wifi radio, a Bluetooth radio, an FM receiver (which in the U.S., at least, is usually turned off by the carrier.)
These radios have varying ranges which depend on a lot of factors.
The cell duplex radio has a theoretical range of about 45 miles. Its typical range (outside urbane areas) is closer to 10 miles, which is the usual spacing between towers in a cell phone system.
The GPS receiver is tiny and has a range of over 15,000 miles in receive mode. True a GPS satellite weighs about a 1000 lbs. and no doubt qualifies as what GURPS 4e calls a Very Large Communicator. However a Very Large Communicator is only suppose to have a range of 10,000 miles. GPS orbits at 12,656 miles and signals from lateral distances will be even greater.
FM ranges are on the order of 40 to 60 miles. Even using the half cost function of receive only radios a Small communicator would still be half a pound vs. the ounce or so of a cell phone FM chip.
A cell phone designed under the communicator rules would weigh about 20 lbs and cost $5000.
So why are the rules broken? Mostly because radio communication is hard. That is, there are many details that determine what the range is for a particular set of radios under particular conditions, which are difficult to capture in RPG rules.
One detail is the size of the antenna. Cell phone usually have really crappy antennas. Your typical cell phone would get much better range if it had a better (in this case better means bigger) antenna. Of course you'd probably feel pretty dorky with a big old dipole antenna sticking out of your iPhone.
Another is power. GPS satellites transmit at about 500 watts. FM transmitters broadcast in the kiloWatt range. Most Cell phones have two signal strengths: .6 watts and 3 watts. Bluetooth devices typically transmit in the 100mW range.
Note that GPS satellites have much weaker transmitters than FM, yet have much greater range. This is partially due to the frequencies they operate at, because frequency band also has an effect upon range. It effects things like whether the radio is line-of-sight or can utilize skip. Skip or skywave is what allows Ham radio operators to talk to Moscow from a set in Tampa.
So we've established GURPS radio communicator rules are broken. What do we do now? We can replace them with house rules based on real world radio communication factors or we can go Hollywood, and just decide what rules work best for our game world based upon the effects we want to see in the game.
In my game I pretty much stick to GURPS 3rd Edition rules for my spacecraft communication systems outside the Grand Route Hypercable system.  So ships and vehicles in the Wilds, Midlands or in the Highlands off the Major Routes use ranges from the Vehicle Design System.
I treat anywhere that has Hypercable as connected all the time, just as I hope most of you are connected to the cell network all the time. (Isn't that a nice fantasy?)
The Highland version of the cell phone, the CMC, is likewise connected through the wireless broadband network in most villages, cities and homesteads. Settled places will have repeaters installed to allow the devices to relay into the wider system.
Spacers will use their ruggedized CMCs to communicate with orbiting spacecraft through the communication systems in their HUVs or brakes, and directly with each other with reasonable distances (see the upcoming CMC entry for details.) And they will work on board their ships using the ship's internal wireless network.