Why does my radio reception improve at night?

[Freakin]

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I believe it is because during the day time there is more pollution, telephone calls and general humn activity, which all, in some way, distort the passage of the sound way from the receiver to your radio.

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That may be part of it, but there is also a big natural phenomenon that causes it, too.

I just wish that I could remember what it is.

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Have you not read any of the other posts in this thread, Cola? It's ionization of parts of the atmosphere.

Also, your Alizee avatar is an acceptable subsitute for now.

Freakin

[B Dids]

ionisphere or something- right? I should know this my dad and grandfather both worked in radio their whole lives. (which makes my dad sound dead, which he's not).

[AngryCola]

Oh yeah, I had read that.

I guess that I had just temporarily forgotten... already. [img]/images/graemlins/grin.gif[/img]

[IsaacW]

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I believe it is because during the day time there is more pollution, telephone calls and general humn activity, which all, in some way, distort the passage of the sound way from the receiver to your radio.

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That may be part of it, but there is also a big natural phenomenon that causes it, too.

I just wish that I could remember what it is.

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During the day, there is a layer in the ionosphere called the D layer that totally hoses communications over long distances. At night the D layer mostly disappears and the signals bounce of the more well-behaved F layer, providing for super-long distance communications.

[Freakin]

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Oh yeah, I had read that.

I guess that I had just temporarily forgotten... already. [img]/images/graemlins/grin.gif[/img]

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lmao. How do you manage to sit through a hand of poker? [img]/images/graemlins/wink.gif[/img]

Freakin

[James Boston]

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night the D layer mostly disappears and the signals bounce of the more well-behaved F layer

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Imagine a bouncy ball being bounced in a room with a 5ft ceiling. Now imagine it being bounced with the same amount of force, but a 20 ft ceiling. This applies mainly to AM's because FM stations all have a similar amplitude that is less affected by the ionoshpere. That is also why, in the US, FM's can operate at 100,000 watts and AM's can only go up to 50,000 (and that's just a select few). Most either have to power down or sign off when the sun sets.

[wacki]

The sun makes our ionosphere, which does three things in Earth's
radio-wave environment:
1) being conductive, it reflects low-frequency radio-waves back to earth.
2) being only partly conductive, it absorbs radio-waves near the cutoff
frequency for such reflection.
3) it makes radio-wave noise ("static") at low and medium frequencies.

http://www.newton.dep.anl.gov/askasc...9/eng99322.htm

[witeknite]

Ding, ding, ding. We have a winner. When the sun goes down, you get more bounce and less absorbtion.

WiteKnite

[jar]

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This applies mainly to AM's because FM stations all have a similar amplitude that is less affected by the ionoshpere. That is also why, in the US, FM's can operate at 100,000 watts and AM's can only go up to 50,000 (and that's just a select few). Most either have to power down or sign off when the sun sets.

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Um, no. Difference in propagation has nothing to do with the type of modulation (AM vs FM). The reason for the difference is that the AM broadcast band is in the Medium Frequency (MF) portion of the spectrum (300khz - 3MHz). MF waves will bounce off of the iononsphere. Because of the differing layers, as explained above, this works better at night. If there isn't a co-channel interference issue (closer station on the same frequency), MF can propagate several thousand miles.

HF(3-30MHz), where so called "shortwave" broadcast, and most non-local Amateur activity is, can propagate around the world, depending on conditions.

VHF(30-300mHz), which is where FM broadcast and most local Amateur activity is, is limited mostly to line of sight propagation. There are conditions where VHF can go over the horizon, but they're rather short lived and tough to predict. Also, over horizon propagation is much more common on low VHF around 50MHz, than up toward 100MHz where FM broadcast is.

Amateur radio is my other(besides poker) geeky hobby [img]/images/graemlins/smile.gif[/img] I hold the Amateur callsign N3SX.

[MicroBob]

Right...and because of the more-bounce effect a lot of low-power stations are forced by law to cut-down their power or else they could be heard in far-distant markets (like the 50k clear-channels get to do every night) and there would be too many stations crossing-over each other.


In some areas though the FCC REALLY over-compensate on how much they make the low-powers go down in strength making their night-time signal virtually meaningless.


When I was in Florida I worked on an AM station that was 1000 watts during the day but at sun-set had to cut down to 68 whopping watts.
That's right...you get more wattage out of a regular light-bulb than the radio station had.
It couldn't even cover the very small city I was working in.

It was only allowed to stay at higher power during emergencies (hurricanes for example).


The FCC regulations are indeed necessary or else all the stations would be crossing over each other and you would have chaos. But the little stations basically have no chance...and there wouldn't have been much harm to letting that station stay at 300 watts or something.


before the governemtn took control and anyone who wanted could start a station in their basement at whatever frequency they wanted there was some REAL chaos.

In 1920 or so WLW in Cincinnati would sometimes go to 500k watts. The modern-day max is 50k watts and on WLW's clear-channel that is strong enough to be heard anywhere east of the Rockies on a good night.

So you can imagine how ridiculous it was when they were at 500k watts. But I imagine they were just trying to clobber all the others that were also on their same frequency at 5k-10k watts or whatever.