Practical takeaway
Symptoms, causes, and cures for overdrive, overload, distortion, consumer-electronics interference, and RF feedback.
T7B · 11 pool questions
Interference, Distortion & Common Problems
Symptoms, causes, and cures for overdrive, overload, distortion, consumer-electronics interference, and RF feedback.
Technician exam focus
This group contains 11 questions in the current pool. The teaching below keeps the important tested terms visible while explaining what they mean in normal Amateur Radio use.
1. Bad audio is often a level problem
If an FM handheld/mobile is over-deviating, reduce the audio level — for example, talk farther from the microphone. RF feedback can also make transmitted audio distorted or unstable; moving cables, improving station grounding/bonding, and using ferrite suppression can help.
2. High SWR can make a modern rig reduce power
A modern solid-state transmitter may automatically fold back its output when it sees high SWR to protect its RF output transistors. Low output power therefore does not always mean the final amplifier has failed.
3. Find out where interference is entering
Before blaming the neighbor’s device, verify that your own station is operating cleanly. If your transmitter is clean but a consumer receiver is being overloaded by your fundamental signal, a filter at the affected receiver’s antenna input may help. If your transmitter is producing harmonics or spurious output, fix or filter the transmitter instead.
4. Overload is not the same as a bad transmitted signal
A perfectly legal, clean nearby signal can overload a poorly protected receiver. Troubleshooting is about identifying whether the unwanted energy is being generated by the transmitter or merely entering the victim device through an unintended path.
T7B checklist
- FM over-deviation: reduce microphone audio level / talk farther from the microphone.
- High SWR can cause transmitter power foldback.
- First verify that your station is functioning properly.
- Receiver overload may be reduced with a filter at the affected receiver input.
- Transmitter harmonics/spurious output must be corrected at the transmitting station.
- RF feedback can distort transmitted audio.
Exam scope: NCVEC 2026–2030 Technician Class (Element 2), effective July 1, 2026 through June 30, 2030, with February 19, 2026 errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool