HD reception day vs. night

I think it has more to do with temperature than sunspots.

If it was temperature than i think it would also have to do with the density of the air. The density of the air doens't change that much within a 10 degree or so temperature change. Maybe it might have an effect when like this winter it was well below zero, signals traveled well that day. I just dont understand, i am not able to get ABC hd and then all of a sudden when the sun starts to go down, dusk, all of a sudden signals are recieved.

[quote="[email protected]"]If it was temperature than i think it would also have to do with the density of the air.

Here is a good site for understanding VHF and UHF signal propagation.
Should be good for ATSC and NTSC formats.

http://www.dxfm.com/

Go down the left column and click on - Signal Propagation

Weather Suitable for a Duct - Tropospheric ducting most often occurs because of a dramatic increase in temperature at higher altitudes...

A radiation inversion forms over land after sunset. The Earth cools by radiating heat into space. This is a progressive process where the radiation of surface heat upwards causes further cooling at the Earth's surface as cooler air moves in to replace the upward moving warm air. At higher altitudes the air tends to cool more slowly, thus setting up the inversion. This process often continues all the way through the night until dawn, sometimes producing inversion layers at 1,000 to 2,000 feet above the ground.

Jason- Most likely you are seeing the

Jerry Keller writes:
If you do not receive the station at all, it is probably not on the air until primetime.
Jerry

Could it be that the station is only broadcasting a HD signal during primetime and a SD signal the rest of the day?

Could it be that the station is only broadcasting a HD signal during primetime and a SD signal the rest of the day?

Source doesn't matter - it's still sending out a 720p or 1080i signal all the time on the same ATSC channel.

There's no reason for a station to only turn on their ATSC broadcast at night. They just upconvert the NTSC feed during the day if there is no HD programming.

Source doesn't matter?????

Digital broadcast is not necessarily a HD broadcast. I get plenty of digital OTA signals during the daytime that are not HD.

Maybe we aren't talking about the same thing. I guess I thought the original question was about getting a digital signal that wasn't HD during the day.

I meant that whether a DTV station is showing an upconverted SD program during the day or a HD program in primetime has no effect on whether you can receive the broadcast signal. The signal is the same. e.g. ABC is sending a 720p atsc signal in both cases, all the time.

I think the question was whether the ATSC channel was only broadcasting at night when HD shows were available but at least in all cases I'm aware of that doesn't happen.

Reception has nothing to do with the programming and everything to do with the environment and sometimes the equipment.

I meant that whether a DTV station is showing an upconverted SD program during the day or a HD program in primetime has no effect on whether you can receive the broadcast signal.

Very true.....I obviously misinterpreted his question. I thought he was asking why he could receive HD at night but not during the day. My thinking was that the OTA stations didn't broadcast in HD 24/7 anyway.
The signal is the same. e.g. ABC is sending a 720p atsc signal in both cases, all the time.

I think the question was whether the ATSC channel was only broadcasting at night when HD shows were available but at least in all cases I'm aware of that doesn't happen.

Reception has nothing to do with the programming and everything to do with the environment and sometimes the equipment.

I understand that completely.....I misunderstood the question....thought it was about HD content.

My bad.....Mike