--- In LPFM_Radio@..., "dinorex200" <kermath@...> wrote:


> If we go for 88.4, mai fm has quite a strong signal. Do you think it
> will affect my signal or degrade it in anyway, and if so, do you
> think we can ask them to limit their frequency range in howick, as
> they are only supposed to be on 88.6

The first answer is yes. Mai FM's licence is for an EIRP of 40dBW off
the Sky Tower, therefore its presence will be quite strong in your area.

They ARE only on 88.6! Their carrier is rock solid on 88.6 in fact.

Why then do I hear part of their signal on 88.4 I hear you ask. Well,
it's HOW the FM modulation system works.

Commercial FM broadcasting requires 150 KHz of bandwidth to transmit a
15 KHz audio signal, with deviation limited to +/- 75kHz and allowing
for a 25kHz guardband.

So effectively what you have is deviation from 88.6 to 88.45 in the
lower sideband and 88.6 to 88.75 in the upper.

The average FM receiver has limited selectivity below 100kHz, so you
hear part of the signal at 88.4.

FM licences are allocate at 400kHz (at the moment) to allow separation
of the frequencies - so the closest frequency you can use to 88.6 is
88.2. This will ensure that you don't have much in the way of
interference.

I hope this has helped answer your question.