Further to Richards comments

You can also model a passive repeater reasonably easily. With a
propagation modelling pgm (eg Radio Mobile, UKWTools etc) find out what
the receive signal level will be at the "repeater", then do a coverage
study with that signal from the repeater site.

In my experience the signals are very low and not often worth it. I was
however involved in a setup to get signal on 400MHz into a railway
cutting from a TX site only 1800 metres away. The measured signal in the
cutting was about -107dBm but with the passive setup that came up to
about -87dBm. In this case the cutting was on the side of a mountain (ie
no other usable reflections) and the useful distance from the passive
repeater was only about 200 metres. The repeater was a 14dBi yagi
pointed at the distant TX site coax connected to a 8dBi yagi pointed
down the cutting.

Cheers Bob W5/VK2YQA

Richard Harrison wrote:

Ian wrote:
"Can a passive repeater work on my cell phone?"