The idea is to have game participants find a channel on a CB or Short Wave radio with a message as a clue. Some of the channels have "radio static", only one channel has a radio message. The message sounds like a NOAA radio weather broadcast. In our use case, we used a message from a national park broadcasting station or ranger station giving safety instructions. Inside the message is a clue.

An actual vintage CB Radio was used. We hacked the radio, stripping its guts and hacked the radio rotary channel selection switch terminal connections to play "radio static" on several channels. On one of the channels, we made the connection play a park ranger’s safety message.

The gag was accomplished with a vintage CB Radio, vintage CB Speaker (mono), a MP3 player (amplifier), and some electronic relays. The MP3 player reads from an SD card and loops automatically on power up. The MP3 player is playing continuously, as long as it receives power. The static or message can’t be heard on dead channels. The message is looped, as would any continuous park message.

The stereo output, each channel (left and right) from the MP3 player is sent to a set of relays. When the CB is in a channel position to play static, RELAY 1 is triggered, allowing the left channel to reach a mono (single channel) speaker. When the CB is on a specific channel, i.e. channel 13 (only one correct channel), RELAY 2 is triggered, allowing the right channel to reach the single channel speaker. The relays work in a mutually exclusive manner, only one is allowing a channel (left or right) to reach the speaker. Some channels result in no sound to reach the speaker.

To better explain, we used DPDT (Double Pole, Double Throw) relays. The normally open poles pass through the speaker connections (complete the circuit). When the relay gets power, the connections are completed, allowing the audio signals to pass through the relay’s normally open switch (since these will close when the relay is energized).

We used Audacity, a free, open source audio software to create a message on the left channel for the static and the actual message on the right channel. The duration of the sound bites both channels are the same. A stereo version of the audio is saved as an MP3 file that is loaded onto an SD card.

The setup is very low tech and very reliable. Again, KISS (Keep It Simple Stupid) wins.

Parts List

Vintage CB Radio (Ebay)
uxcell 10 x DC 5V Coil 8 Pins DPDT Power Relay HK19F (Amazon)
ARCHEER Mini Karaoke Machine Power Amplifier (Amazon)
Mono External CB Speaker (EBay)

A 12vdc power supply is used to trigger the relays and allow the back light of the dial to work and any other mini incandescent light bulbs to light up.

Also, You will need the same or another 12vdc power supply for the MP3 player listed above. It doesn't come with one.

In our game, we enclosed the CB Radio in an acrylic case with a lock on it. Game participants have to unload the case before they get to play with the CB radio and channels.