“A vehicle with a locked-band repeater parked in a moderately favorable location provides near county-wide coverage. ” Bryan KG4UPR
Requirement: true dual-band mobile radio as opposed to dual VFO)
Recommend: learn how to set up your true dual-band mobile radio for locked-band repeater mode. Store the configuration in a Programmable Memory for ready access. Test it regularly.
Mobile Radio Configuration: Locked-band repeating for emergency use would typically have the mobile radio set to receive on an appropriate UHF frequency (e.g., 440.850 MHz simplex), and set to transmit on an appropriate VHF frequency (e.g., 147.480 MHz simplex). The UHF input (receive) should have Continuous Tone-Coded Squelch System (CTCSS) enabled.
HT Configuration: A dual VFO HT configured to use the locked-band repeater would have its transmit VFO set to the the UHF input frequency (with output tone configured to match the locked-band repeater CTCSS), and likewise its receive VFO would be set to the VHF frequency of interest. Typically the HT is going to be in close proximity to the locked-band repeater, so the HT should be set for the minimum power level necessary (e.g., 0.5 W). It’s possible with some radios to remotely adjust the operating configuration of the locked-band repeater using DTMF tone strings.
Gary Pearce KN4AQ has a tutorial for getting started: