With regards to the original question, 500mW in the FM broadcast band
can easily travel 50km with the right antenna setup.
I have set up studio links that travel 30km using 100mW link gear.


--- In LPFM_Radio@..., "Steve" <nzyes1@...> wrote:
>
> I recently bought a 0.5 watt FM transmitter on ebay.
> But it can only reach about 100-200 metres a slightly better coverage
> than the ipod wireless transmitter.
> I wonder if this has real 0.5 watt output or I need to put a nice
> outdoor antenna, cos I tested with indoor antenna included with the kit.
> Anybody knows how to measure transmission output?
>