In this paper, the problem of experiment design in single input single output (SISO) single carrier (SC) systems under a deterministic channel assumption is investigated and several connections with optimal preamble designs in multicarrier (MC) systems are established. In the context of SC systems, we derive optimal input sequences for the least-squares (LS) channel estimator under an input energy constraint. We then establish certain connections to optimal input designs for LS frequency domain channel estimation in MC systems. These connections reflect similarities between SC and MC systems both quantitative, i.e., in the achievable mean square error (MSE) performance, as well as qualitative, i.e., in the actual optimal input sequences. Simulations are provided to support the derived results.