It was a simpler time sixty years ago, and this electronics hobbyist and aviation enthusiast was able to walk out onto the tarmac with her suspicious electronic device, as shown on the cover of Popular Electronics, July 1957.
She is listening to aircraft traffic with a simple VHF receiver, and the plans are shown in the magazine. The set was a crystal set using a 1N82 diode, with one CK722 transistor for audio amplification and tuned 90-145 MHz. In addition to being useful for listening to aircraft, the magazine said that it could be used to zero in with bloodhound accuracy in a hidden transmitter hunt.
In testing the set at a local airport, the tower could be heard several hundred feet away and approaching planes could also be heard.