Radios solve many problems that may stand in the way completing a quest. Instant communication is a powerful technology in the context of adventurers needing to get word to someone else about something urgent.

If radio (and/or mobile phone) technology exists in your campaign, make a list of different reasons why it might not work at any given time. Then when your heroes decide they can shortcut part of the adventure by radioing someone, you have a handy selection of complications to throw in their way. The bigger your list, the better your chance of finding something plausible - and of avoiding the constant "no signal" that you see a lot in movies and TV shows these days.

Some to get you started:

• "No signal" - yeah, it's boring, but it's an option.
• Battery is dead.
• Battery fell out.
• Someone forgot to install batteries.
• The transmitter or receiver doesn't have the range. (One way communication might be possible.)
• There is some natural material in the area that blocks the signal (e.g. sand).
• Something solid in the way: a building, a mountain, a planet. (Conventional radio signals don't travel through solid material very well.)
• Natural electromagnetic interference. e.g. thunderstorm, solar flare, ion storm, plasma discharge, ionised region of space.
• Artificial interference: deliberate jamming, or unintentional interference from nearby technology.
• The radio is actually broken. Perhaps it got damaged in a recent battle, or by jostling. Or maybe a component just failed.
• Someone broke the antenna off to use as a lockpick.
• Sabotage.
• The radio is just missing for some unexplained reason (which may be explained later).
• Intended recipient is asleep and has receiver on "do not disturb".
• Receiver is holding down the talk button, so can't hear you.
• Background noise (on either end) makes it impossible to hear what the other person is saying clearly.
• Person at other end is going through a tunnel.
• Person at other end is interrupted and has to stop talking. (Double points if they are captured or killed by the villain mid-call!)
• Person at other end is not speaking to you after an earlier comical misunderstanding.
• You get through to someone, but the person at the other end doesn't understand your language.
• Parties are unable to convey their message without body language and other visual cues.
• Call is intercepted by an unexpected party, who refuses to cooperate. Refer: Jolyon Wagg in The Calculus Affair.
• Every frequency is in use by a smooth jazz music station with a 100 gigawatt transmitter.
• Receiver and transmitter are accidentally tuned to different frequencies.
• Relative motion causes Doppler shifts that mismatch frequencies.
• Intended recipient is travelling away from you at (or above) the speed of light.
• Radio requires a licence fee to be paid.
• You need to listen to an ad first. (Good for situations where it's so urgent that a 30 second delay would be critical.)
• Radio requires a software update... Downloading..... 4% complete.....
• Development of new communication standards has reached a pace where the format you send it in is obsolete by the time it reaches its destination.
• Energy-based lifeforms that eat radio waves.
• Local disturbance of the permitivity of free space constant, for nefarious purposes.
• Attacked by a goose.
• Volcanic eruption!
• Radio is actually a cake.
• Existence is an illusion, including the bit about radios.
• The signal goes through partially silvered mirrors and interferes destructively with itself.
• You're inside a black hole, so the signal can't get out.
• One party misunderstood the phrase "ham radio" and is talking into an actual ham.
• The recipient is in another galaxy, so by the time you reply to their message, their civilisation has died out.
• Sender and receiver in different dimensions/universes/times/timelines.
• You have joined a religious order that requires a vow of silence.
• You and receiver are at different levels of Inception.
• All you hear is Radio Ga Ga.
• Video killed the radio star.
• Divine intervention.
• Also they're confused why you keep answering questions they haven't asked yet. Recipient experiences universe with a reversed arrow of time, and your responses are both nonsensical and infuriating to them.

Transcript

GM: Rey, you notice BB-8’s antenna is bent.
Rey: Let me fix that.
BB-8: Actually it’s not that simple. My pilot, Poe Dameron, kinda... defected to the First Order.
Rey: That’s a hell of a complication to lay on straightening your antenna.
BB-8: We need to get back to the Resistance to warn them that Poe can’t be trusted.
Rey: Or we could, you know, radio them.
GM: The sands of Tatooine block signals, remember.
Rey: Or not.
{beat}
Rey: I hate sand.