If several channels are being transmitted from one location

cycler

DTVUSA Member
#1
Isn't it logical that all of them ought to come in the same?

I went to the website for WLIW Channel 21 in NY and it had an interesting bit of information. Channels 2, 7, 11, PBS and 21 are all broadcasting from the Empire State Building. I get all of them perfectly except for 21.

They also mentioned the "double scan" which was mentioned on this site and I did but that still doesn't allow me to receive the channel.

I know that it's relatively unimportant considering the serious difficulties that some people are experiencing but it doesn't seem logical to me now that I know that they are all being transmitted from one location.
 

Squire Dustin

DTVUSA Jr. Member
#2
There are several reasons why stations broadcasting from the same location may not be received equally.

1) Not all stations are full power. Some have stronger signals than others
2) Frequencies are different. This means propagation effects such as multipath are different.
3) The actual location of the transmitting antenna on the building could affect the received signal at your location.

With the above said, you still might be able to get it on your list if you try a scan at different times of the day and in different weather conditions. You still will probably not be able to receive it 100% of the time.
 

Don_M

DTVUSA Member
#3
What he said. My experience is that greater transmission-antenna height counts for much more than higher power. Here in Denver, we have two DTV stations whose antennas are on the same tower. The 1,000-kW station's antenna is located just 18 meters below the 800-kW station's antenna. That's right: The lower-power transmitter is noticeably easier to pull in, even at 20 percent less power.
 

Piggie

Super Moderator
#4
What he said. My experience is that greater transmission-antenna height counts for much more than higher power. Here in Denver, we have two DTV stations whose antennas are on the same tower. The 1,000-kW station's antenna is located just 18 meters below the 800-kW station's antenna. That's right: The lower-power transmitter is noticeably easier to pull in, even at 20 percent less power.
Don, pure guess. But I bet the higher antenna is top mounted, and lower one is no doubt side mounted. Even a good 4 panel array that has special mounts to make a square around a triangular tower still never has the "ears" the one on top has.

I am guessing at only 18 meters difference this is likely the cause.

BUT! (with RF is are always buts) It could be the difference in antennas period, as not all of them are the same just like home models.

But the deal of being on top in the clear started the whole candelabra deal. Where you can mount at least 3 antennas straight up. Some candelabra's are so high about the tower, you can hang 3 more down.

This is good for the stations and the tower owner.

Now back to the ESB. I don't know how they are mounted there. Or if they have one very thick all band antenna. But it could be just the location on the ESB that causes the problem. If that is so, its possible that different viewers in different directions have trouble with different stations. Unless the 21 antenna just isn't that good or has a problem.

Another factors (see RF and it's buts) is down tilt. Down tilt is a good thing as it puts more signal close to the antenna and it also hits the knife edge of the horizon with more signal to knife edge over. Not everyone but most now use down tilt. Most down tilt is only 1 degree.

If you have never seen an engineering report on a TV transmit site, it's interesting.
 
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