Hack the Planet (not ours)

Michelle Thompson of Open Research Institute describes an amateur attempt to echo a radio signal off Venus and receive it on Earth, with enough structure to carry data. The 2009 AMSAT DL test only returned a bare carrier. Venus is very far away, so the path loss is enormous, and its slow spin smears the echo across frequency. The talk starts from the link budget, which is expressed in decibels per hertz so the numbers can be compared across bandwidths.

The team checked its model against four echoes measured in March 2025 and found the prediction within about a tenth of a decibel. For the October attempt the reflectivity is lower, so the link would fall short without help. The 100-meter Effelsberg dish adds roughly 13 dB, which closes the margin. Spin-induced Doppler spread limits coherent integration to about a third of a second, a penalty the speaker calls the coherence time tax. Zadoff-Chu sequences were considered, but they still cannot beat that limit.

The custom waveform, designed by volunteer Pete Wickoff, uses coherent frames sized to the coherence time, widely spaced tones, and non-coherent combining across many frames. It uses a 496-symbol orthogonal alphabet to gain power efficiency. The moon serves as a harsher but stronger test channel for smaller stations. The main takeaway is to model the channel first and let its physics shape the signal design.