In radiotelephone communications, what is the correct sequence for SSB-Voice without carrier, USB-Voice with carrier, FM-Voice, and SITOR (NBDP) TELEX?

The correct answer is based on the standard designations for different types of modulation used in radiotelephone communications.

In the sequence provided, J3E represents Single Sideband (SSB) Voice without a carrier, which is a common and efficient mode for voice communications, particularly because it allows for better clarity and lower power usage compared to amplitude modulation. Next, H3E stands for Upper Sideband (USB) Voice with carrier, which is another voice mode that also utilizes single sideband techniques but includes a carrier component to enhance signal transmission quality, especially in longer-range communications where signal fading might occur.

Following these, F3E is the designation for Frequency Modulation Voice, which uses varying frequencies to encode voice signals and is common in two-way radio systems. Finally, F1B refers to the Facsimile with modulation, representing the SITOR (Simplex Telex Over Radio) or Narrow Band Direct Printing (NBDP) communications mode, typically used for sending data and text-based messages rather than voice.

This order reflects the hierarchy and logical use of these modulation techniques in radiotelephone communications, making it clear why the provided sequence is the most accurate representation of these modes. Each designation leads to specific applications in the realm of