An uncertainty model of total radiated power (TRP) measurements in a reverberation chamber (RC) has been proposed in a previous work, where it was hypothesized that the signal bandwidth had no effect on measurement uncertainty. However, our recent experiments indicate that the signal bandwidth of a long-term evolution (LTE) device indeed affects TRP’s measurement uncertainty. In this article, we investigate the effect of signal bandwidth on TRP tests and improve the uncertainty model to include this effect. It is shown that a larger LTE signal bandwidth helps reducing TRP uncertainty. This phenomenon can be well-captured by the improved uncertainty model, which is further validated by two sets of TRP measurements with different signal bandwidths.