ARRL Technician Practice Exam

Which type of voice mode is most often used for long-distance (weak signal) contacts on the VHF and UHF bands?

1. AM

2. FM

3. SSB

4. ISB

The correct answer is: SSB

The most common voice mode used for long-distance, weak signal contacts on the VHF and UHF bands is Single Sideband (SSB). SSB is an efficient form of amplitude modulation that uses less power and bandwidth compared to traditional amplitude modulation (AM) or frequency modulation (FM). This efficiency makes it particularly well-suited for long-distance communication because it can effectively carry voice signals over greater distances, especially in weak signal conditions where clarity is essential. SSB transmission involves suppressing one of the carrier waves along with the redundant sideband, which results in a signal that occupies less bandwidth and is less susceptible to noise and interference. As a result, operators can communicate more effectively, even when signals are weak or when the conditions are not ideal for other modes. In contrast, AM and FM are generally more suited for local communications because they require more bandwidth and power to maintain clarity and quality. While they may work for shorter distances or when signals are strong, they are less effective for weak signal long-distance operations. ISB, or Independent Sideband, is a more complex form of modulation that is not commonly used among typical amateur radio operators on VHF and UHF for voice communication, further emphasizing the utility of SSB for these conditions.