Goofs

At around 25 minutes in, when Cliff Robertson is getting ready to leave the transmitter room, he puts his jacket on and then when he exits the transmission room to go outside, he is again putting his jacket on which he had already done.

Toward the beginning, the cars in the parking lot change positions or disappear altogether in shots taken just seconds apart.

Alan discusses radio signals with the Galaxy Being, who is located in the Andromeda Galaxy. Radio waves, like all electromagnetic waves, travel at the speed of light. Since the Andromeda Galaxy is 2.5 million light years away, it would take any single radio messages 2.5 million years to go one direction, making any immediate communication impossible.

When the DJ increases the power output of the transmitter, it causes the radios tuned in to that station to become much louder in sound volume. The sound volume is controlled by the receiving radio, not by the power output of the transmitter. Increasing the transmitter's power would expand the range of the transmission, not the sound volume or loudness at the receivers.

Alan Maxwell attempts to use the pay phone three time in a row. The second time, he retrieves his dime without having had to hang up first. Pay phones of that era would release your coin(s) back to you if your call didn't go through, but only once you hang up the receiver.

When the low power output of the station is discussed, the camera zooms in on a VU meter. VU meters show sound levels and not power levels.

When Eddie Phillips turns up the station's power, the meter seen is an AC Voltmeter, not an RF power output meter.

Radio announcer at beginning says station is brought to you at 1820 on the radio dial. AM radio frequencies only range from 540 kHz up to 1700 kHz, in 10 kHz steps.

The producers knew this, and deliberately used an "impossible" frequency so as not to use a frequency used by real-world stations.

If the station's frequency of 1821 was indeed 18211821, it would have so many numbers it would go across nearly a third of a normal radio dial, but DJ Buddy Maxwell calls out "eighteen-twenty one - (that's) one, eight, two, oh," repeating the numbers individually for clarity.

The call letters of the radio station are KXKVI. Radio and TV stations have three or four call letters only, such as WOR, WABC or KRLA, not five. TV stations have the suffix -TV after the call letters.

However, the producers of the show would have known this. Using "impossible" call letters would have prevented the use of the call letters of any actual radio station.

The creature goes into a music shop. All the instruments are seen in negative mode (the guitar looking as if lit from within) because the effect for the creature is applied to everything in the scene.

The alien tells the human to move his finger due east on the star chart; however, in space there are no normal compass-based directions since these relate to a planet while on the planet. The alien could have said left or right and been correct.