Basic Qualification · B-008 Interference and suppression · B-008-001-009
Two mobile stations are communicating through a repeater. As they arrive in close proximity to each other, they begin to have difficulty communicating. What is the most likely cause?
- A Transmitter signals are desensitizing the receivers
- B CTCSS tones are activating the receivers' squelch circuits
- C They have entered a null area of their antenna patterns
- D Transmitter signals are mixing with the repeater signal to cause intermodulation
Correct answer: A — Transmitter signals are desensitizing the receivers. From the official ISED question bank, verified word for word.
Why
When two mobile stations get very close while using a repeater, their strong local signals can overwhelm the repeater's receiver, a problem called desensitizing. The full explanation — and one for every question — is in Pro.
Practise this section
When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.