Over on YouTube F4IPO has posted a video of him using a KrakenSDR and the KrakenSDR Android mapping app to quickly locate the source of a TETRA transmission at 427 MHz in France.

The KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding and passive radar. We successfully crowd funded the device on Crowd Supply.  

In the video F4IPO shows a dash cam recording of his vehicle alongside a screen recording of his Android phone screen. He makes use of the auto-navigation feature which navigates him right to the radio transmit tower. He notes that the entire process to locate the transmitter only took about 5 minutes. At the end of the video he shows the antenna setup on his roof.