VHF radios are relatively easy to locate by direction finding techniques, using for example a doppler direction finding array. The FCC's enforcement division is

VHF radios are relatively easy to locate by direction finding techniques, using for example a doppler direction finding array. The FCC's enforcement division is well-known to possess SUVs with this kind of equipment discreetly installed, although due to their famously limited budget you aren't too likely to see one in the wild. On the other hand, though, many large airports have such equipment permanently installed (e.g. RFEye).