A person with an ICM or loop recorder may need to keep the antenna of a radio transmitter a safe distance from their heart monitor. Stay at least six inches away from two-way radio transmitters. Stay at least 30 inches away from a portable radio transmitter antenna. Stay at least 24 inches from a commercial or government vehicle-mounted radio transmitter antenna. For transmitter antennas of transmission power levels between 125 and 250W, keep at least nine feet away. Check with the ICM's manufacturer to confirm any additional restrictions.