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We study radio emissions from positive streamers in air using 3D simulations, from which the radiated electric field is computed by solving Jefimenko’s equations. The simulations are performed at 0.5bar$0.5\,\mathrm{b}\mathrm{a}\mathrm{r}$using two photoionization methods: the Helmholtz approximation for a photon density and a Monte Carlo method using discrete photons, with the latter being the most realistic. We consider cases with single streamers, streamer branching, streamers interacting with preionization and streamer‐streamer encounters. We do not observe a strong VHF radio signal during or after branching, which is confirmed by lab experiments. This indicates that the current inside a streamer discharge evolves approximately continuously during branching. On the other hand, stochastic fluctuations in streamer propagation due to Monte Carlo photoionization lead to more radio emission being emitted at frequencies of 100 MHz and above. Another process that leads to such high‐frequency emission is the interaction of a streamer with a weakly preionized region, which can be present due to a previous discharge. In agreement with previous work, we observe the strongest and highest‐frequency emission from streamer encounters. The amount of total energy that is radiated seems to depend primarily on the background electric field, and less on the particular streamer evolution. Finally, we present approximations for the maximal current along a streamer channel and a fit formula for a streamer's current moment. The lightning channels in a thunderstorm are preceded by smaller discharges, so‐called streamers, which propagate at velocities of hundreds to thousands of kilometers per second. We cannot see these streamers from the ground, but we can detect their radio emission. However, it is currently not fully clear what the main mechanisms are by which streamers produce radio emission. In this paper we therefore perform 3D computer simulations of streamers under different conditions, from which we compute the resulting radio emissions. We find that streamer branching (the splitting of a streamer channel in two new ones) does not lead to a significant radio signal, which we furthermore have confirmed with lab experiments. We also show that small fluctuations in a streamer's propagation, which should also occur naturally, lead to radio emission at higher frequencies than in the absence of such fluctuations. Several other cases are also investigated, such as a “collision” between two streamers and streamers in different background electric fields. Streamer branching does not lead to significant radio emission in our simulations and lab experimentsStochastic fluctuations during streamer propagation increase radio emission at frequencies of 100 MHz and aboveWhen streamers encounter an already partially ionized region, their properties rapidly change leading to emissions up to several 100 MHz Streamer branching does not lead to significant radio emission in our simulations and lab experiments Stochastic fluctuations during streamer propagation increase radio emission at frequencies of 100 MHz and above When streamers encounter an already partially ionized region, their properties rapidly change leading to emissions up to several 100 MHz