ARRL Technician Practice Exam

What is a recommended way to reduce interference from an amateur transmitter to a nearby telephone?

1. Reduce the power of the transmitter

2. Change the frequency of operation

3. Put a RF filter on the telephone

4. Use a different type of telephone

The correct answer is: Put a RF filter on the telephone

Using an RF (radio frequency) filter on the telephone is a practical and effective method to mitigate interference from an amateur radio transmitter. RF filters are designed to block or attenuate unwanted radio frequency signals that may be picked up by sensitive electronic devices like telephones. By incorporating an RF filter, you can effectively reduce the impact of stray RF emissions, allowing the telephone to function properly without being disturbed by the signals generated by nearby amateur radio operations. This solution is particularly useful because it directly addresses the interference issue without requiring major changes to either the transmitter’s operation or the telephone system itself. It allows for continued use of the existing equipment while enhancing its performance against interference. Reducing the transmitter's power or changing the frequency of operation can be beneficial in some situations, but these adjustments may not always effectively eliminate interference, especially if the interference is severe. Additionally, switching to a different type of telephone may not address the root cause of the interference issue, as many modern devices can still be susceptible to RF noise. Using an RF filter specifically targets the interference problem, making it the most practical recommendation.