Hello!

I'm one of the 1.7 million people currently coding a survival game set in a zombie-infested post-apocalyptic world.

Then you have quite a big dev team there

There's an Arma mod called ACRE that adds a semi-realistic radio system.

Maybe you can get some good ideas from the links in their wiki:

http://tracker.idi-systems.com/projects/acre/wiki

You will likely want to sit down and look at the history of radio communications. Post Apocalyptic times will mean a far less cluttered radio spectrum in most cases, as there would be far fewer people transmitting. (Possibly some of it will be less useful due to environmental effects)

So much of it will be cobbled together with different era of tech, depending on what tools and knowledge are available at the time. Totally understandable to have someone transmitting with a very crude spark gap pulse code (morse code) working next to someone with a digital field video point to point radio. One would be something made from materials on hand, the other most likely a surviving relic.

Also don't forget the issues of radio location, bandwidth, and power. It is possible for someone to be heard by you, but you being unable to reply. Someone can use up a huge amount of bandwidth on a high power signal, which drowns out other signals in an area. (It isn't unusual for some radio operators to use max legal power on their signals to talk to someone on the other side of a town, which is basically just their way of showing off big their gear is. Highly annoying to other operators.)

Most probably HAM radio over large distances, and CB radio (like truckers use) or improvised spark-gap transmitters over intermediate/short distances. Those would be most prominent near the beginning of the scenario, and would probably decay/evolve over time as equipment breaks and needs a replacement cobbled together.

A local radio station could be 'taken over' by people and utilized, but usually the transmitter itself is far away, and analog broadcasts require a great deal of power (proportional to their signal range) -- they'd need a significant power source that's still intact, and may have reduced range based on available power.

AM radio can bounce off the upper atmosphere, and with the relatively low amount of other interfering signals and clear skies, can reach a great distance. I remember being young, growing up in Minnesota, we could sometimes pick up AM radio stations from Quebec, Japan, and Russia when conditions were right. HAM radio is the same. This might be a believable way to get news about how the rest of the world is doing if language is not a barrier.

This might be a dumb idea but at the other end of the spectrum I suggest adding satellite radio that doesn't "do" anything but broadcasts old news/music from times before the apocalypse, in an eery sort of way. For instance even if civilization collapsed it's likely there would still be satellites in service for at least 5-10 years (after which their orbit eventually decays). They could also be a minor gameplay element e.g. hacking them remotely or something to increase your communications range :p (that would require advanced technology though)

Again just an idea, I have no idea if this is even plausible, but if it is, then it would certainly seem as though those satellites would have significant strategic importance given their wide range and rather safe position (especially spy satellites).