Question E2A07:
Which of the following types of signals can be relayed through a linear transponder?  

Choices:  
A: FM and CW  
B: SSB and SSTV  
C: PSK and packet  
D: All these choices are correct    

Correct Answer is  D: All these choices are correct  

A linear transponder is a “bent‑pipe” that linearly translates a whole slice of spectrum from the uplink to the downlink. Because it preserves amplitude and phase, any modulation inside its passband is relayed.

Why D (All these choices) is correct
- A linear transponder will pass FM, CW, SSB, SSTV, PSK, packet—indeed, any signal—so long as:
  - The signal fits within the transponder’s passband.
  - The uplink power does not drive the transponder into nonlinearity (compression).

Why the other choices are “incorrect”
- A: FM and CW — true, but incomplete (excludes SSB, SSTV, PSK, packet).
- B: SSB and SSTV — true, but incomplete.
- C: PSK and packet — true, but incomplete.

Useful rules and formulas
- Linear translation (conceptual): the transponder outputs a frequency‑shifted version of the input and preserves waveform shape:
  - Amplitude/phase preserved: if input is $v_{\text{in}}(t)$, then $v_{\text{out}}(t) \approx k\,v_{\text{in}}(t)$ within the passband.
  - Frequency mapping (conceptual): $f_{\text{down}} = f_{\text{up}} + \Delta f$.
- Bandwidth fit: ensure $B_{\text{signal}} \le B_{\text{transponder}}$.
  - Typical occupancy: CW ≲ 500 Hz, SSB ≈ 2.4–3 kHz, many narrow PSK modes ≲ 3 kHz.
  - FM bandwidth (Carson’s Rule): $$B_{\text{FM}} \approx 2(\Delta f + f_m)$$
    where $\Delta f$ is peak deviation and $f_m$ is highest modulating frequency. FM often occupies much more bandwidth and is therefore discouraged on linear birds, but it can be relayed.
- Operating tip: Use the minimum uplink power needed and keep signals narrow to avoid overdriving the transponder and to leave room for others.