Just to add my two cents to the discussion. The Motorola Micor "and squelch" modification is not 100 %. The "and squelch" in the Micor starts to function after the receiver has about .8 uV of signal. Encouraging your users to put their best signal into the repeater will minimize this effect. The Micor book has the mods.
Good luck. As has been pointed out, the audio delay line almost always works.
