Is there a time when radio broadcasts are most powerful?

Question

I read somewhere that during the evening and morning, at dawn and dusk, there is less atmospheric interference when radio waves are broadcast over a long distance. I was wondering if this was in fact true, and if so, how large an effect the time of a radio transmission has on the distance a transmission can be received.

Answer 1

Yes, and no.  Due to solar wind, the ionosphere is affected differently during the day hours than night hours.  The ionosphere expands and contracts. It becomes transparent to some frequencies and more reflective to others.

As a result, some ranges of frequencies get bounced off the ionosphere back down to earth hundreds of miles away while others just slip thru it.  Some frequencies get stronger and some get weaker. Some "bounce" many times as far and others fly off into space.

So to say they are more powerful isnt very accurate. You would have to be more specific about which frequency the broadcast was on.

Due to this effect, many radio stations have to manipulate their output power at dawn and dusk. Some AM broadcast stations are on what's called a clear channel. That means they are allowd to broadcast accross the country. So while most AM stations have to cut their power at dusk (to keep their broadcasts from going further by accident), stations liscensed as clear channel stations actually crank up their power at night so that they can go much further than during the day.

Answer 2

Great question.  Many things can effect the transmission quality/range of broadcast.  There is this phenomenon called Anomolous Propagation.  In simpiler terms, things that effect transmission, such as Temperature, Inversion layers, trapping, ducting, can all efffect the distance and quality of transmission.   The best time to transmit is during a cool, low moisture atmospheric condition.  No fog, no moisture, etc.  Cheers!  

Answer 3

Not really, but reception over long distances does vary by time of day. That's because some signals come to you by reflecting off of atmospheric layers whose altitude varies. Some call these 'skip' transmissions.

Sometimes a signal of only a few Watts can travel thousands of miles.