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radio wave help

B

biferi

Member
Jul 29, 2008
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Someone here told me before that the D Layer of the Ionashpere will let AM Radio Waves pass through it.

If AM Radio Waves Pass through it then how does Shortwave Radio work at all???

Is it because even if the D Layer lets the AM Radio Waves throught they still will hit the other Layers and they will bonce the waves back to Earth?

And does the D Layer all day and night let waves pass through it???
 

Am, FM or SSB has nothing to do with whether or not signals are absorbed by the D-layer. The factor affected by the D-layer is frequency. And contrary to stated beliefs, it does not disappear at night, it simply becomes less ionized and therefore more permeable to RF.
 
Nursecosmo said:
Am, FM or SSB has nothing to do with whether or not signals are absorbed by the D-layer. The factor affected by the D-layer is frequency. And contrary to stated beliefs, it does not disappear at night, it simply becomes less ionized and therefore more permeable to RF.
Click to expand...


The reference to AM radio waves is in regards to the AM broadcast band not mode. Most people refer to AM as 530-1710 KHz and FM radio as from 88-108 MHz. It is true that the D layer becomes less ionized by the absence of gamma radiation at night but the electron density is so low that it is essentially non-existent therefore it can be deemed as having disappeared.
 
thanks but

So if I get what you are telling me?

At night the D Layer is Less Ionized so Shortwave will be Absorbed by it and not Reflected back to Earth???????????????????

So would I be right that just HF get absorbed by the D Layer or does it afected more??
 
biferi said:
So if I get what you are telling me?

At night the D Layer is Less Ionized so Shortwave will be Absorbed by it and not Reflected back to Earth???????????????????

So would I be right that just HF get absorbed by the D Layer or does it afected more??
Click to expand...

No. At night all layers of the ionosphere become less ionized so that the higher bands of HF are not reflected. However, there is usually enough residual ionization for propagation of the lower bands from say, 80 meters on down.

Try here: Radio propagation - Wikipedia, the free encyclopedia

And here: Skywave - Wikipedia, the free encyclopedia
 
biferi said:
So if I get what you are telling me?

At night the D Layer is Less Ionized so Shortwave will be Absorbed by it and not Reflected back to Earth???????????????????

So would I be right that just HF get absorbed by the D Layer or does it afected more??
Click to expand...


The D layer is less ionized and for all intents and purposees disappears at night and allows lower frequency signals to pass thru it and onto more densely ionized layers where it gets reflected back to earth.
 
thanks but

So I think I get it now?

At night the D Layer is Less Ionized so HF that would be High FREQ. Shortwave will be Absorbed and not reflected.

And LF that is Low FREQ. will pass right through it and be reflected off another Layer that is More Ionized?????????
 
biferi said:
So I think I get it now?

At night the D Layer is Less Ionized so HF that would be High FREQ. Shortwave will be Absorbed and not reflected.

And LF that is Low FREQ. will pass right through it and be reflected off another Layer that is More Ionized?????????
Click to expand...

No you still don't have it.

D-layer during the day absorbs more RF (doesn't matter which frequency) at night it's less ionized therefore more RF pass through it so that it can be reflected off high layers.

Forget about frequency that seems to be what is confusing you.
 
thank but

Thanks I get it now
all RF waves Radio FREQ. will be Absorbed by the D Layer in the Daytime because the D Layer is More Ionoized.

And at Nighttime the D Layer is Less Ionized so RF go right through it and gets to the other Layers so it can reflect off them.

But one thing?

If Nighttime the D Layer is Less Ionized so RF goes right though it then wont FR go right though the other Layers as well?

At night they all all Less Ionized so how can any of them reflect?????????
 
Short Answer is no. The layers all have different characteristics, thats why they are layers, so the others do not act the same.
 
Hutch said:
No you still don't have it.

D-layer during the day absorbs more RF (doesn't matter which frequency) at night it's less ionized therefore more RF pass through it so that it can be reflected off high layers.

Forget about frequency that seems to be what is confusing you.
Click to expand...

The D-layer during the day only has significant absorption below 7 to 10MHz, increasing absorption as you go lower in frequency.

But the reason the lower bands like 80m open up at night is because with the D-layer gone, the F2 layer is accessable. The F2 layer looses its steam slowly at night, especially for the lower bands. But the F2 seems to die more quickly at night for the higher frequency HF bands; the MUF drops fast as sun goes down.

I would think the F2 can actually reflect 80m over nearly the full 24 hours a day, but we just cant see it because the D layer gets in the way.
 

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