Thread: OTA reception expertise requested

hi folks,

I have a Radio Shack 360 degree UHF in my attic. I am running 50' of RG6 cable to a bi-directional splitter, providing the antenna reception to OTA adaptors in each of my 722k's.

I am 3.4 miles or less from the towers of my locals. all of them register 90 + consistently on my DVR power measurements.

whenever I am viewing an OTA HD channel on either 722k, I get 1 second audio dropouts every couple of minutes, regardless of the channel. this occurs during live broadcasts(and obviously on recorded material), but does not occur on my locals when viewing the satellite feed.

could this be an OTA module issue(but it happens on both of them). Do I need to mount a different style of antenna, and do a rooftop mount to eliminate this problem, even though my reception power is very high on all local OTA channels?

thanks.

Your omni directional antenna probably has an amplifier built in which you don't need. Put a $5 set of rabbit ears in that attic and see what your reception looks like at 3 miles.

I had this problem with this antenna. Disconnect the amp, and it should clear up.

thanks guys, I do indeed have the amp wired in.

I will remove and see what happens.

will let you know.

thanks!

Omni directional antenna's is not the proper way to receive a UHF signal.

Some buiding materials in your homes construction makes it opaque to UHF signals.

Your best bet is to use a good small directional antenna, pointed in the right direction.

The HBU 22 or the Winegard 7694P are both good examples of a short range combo antenna.

Depending on where you live, you might have VHF signals along with your UHF signals and a UHF antenna does not pick up very well - VHF signals.

JB, he's less than 4 miles from most towers, and they're spread over 110 degrees across the horizon. The omni isn't great, but it's far more practical than another option. VHF reception is not an issue, but beam width is.

Z06, you'd get better results if you could put it on a mast outside. Any chance you can put up a gable mount or a chimney mount for a 1-1/2" antenna mast? You can get what you need at Radio Shack or online, for probably $35 total. You can't use a satellite dish mast with that antenna without heavily modifying the bracket to fit a 1-5/8" mast...ask me how I know.

Omni Directional antenna's don't do much of anything well.

A persons best bet is to have a good combo antenna and point it in the wrong direction.

A omni direction antenna, because it is not directional is very susceptible to multipath.
Multipath is when you have one signal coming from more than one direction at different times because the signal is bouncing off something - being reflected and corrupting the signal.

With analog television this was also called ghosting, because the second signal would interfere with the first - original signal and you would have two pictures at the same time.

With digital, a corrupt signal is worse then no signal at all.

The way the digital tuner works, when a piece of data is missing, it looks at what has already been received. It's all 1's and 0's.

So if you had 5 0's in a row, chances are the missing piece of data is also a 0

So it can guess and try to piece together the information and keep it going.

When you have too much data corrupt, the picture freezes and the audio stops and starts.

Sometimes living too close to the transmitter is just as bad as being too far away.

At other times, if the stick is too high up in the air, it will skip over the most local viewers and will be received 20 to 40 miles away from it's target area.

That is the main reason for the power reduction of the digital transmitter. It is easier to reduce the power and not have to work it so hard to get it to broadcast locally then to increase the power and have it go where you do not intend it to go.

A directional antenna works like a balloon. When you squeeze a balloon in the middle, the ends bulge out away from the middle. The bulge is your gain.
At the same time when you make the balloon bulge, the size or area of the balloon gets smaller in the front and back.

You might hear people mention front to back ratios on a antenna.

How the front to back works is that when the antenna is pointed in the proper direction - it still receives some signals from the back of the antenna. Although in modern communications, you never rely on a front to back because you only point your antenna where you wish it to receive, it is still good to know because the backside is usually where your multipath will come from.

By putting a reflector behind the antenna and only receiving from one direction, you eliminate some of the front to back, which is the reason why a Bay antenna sometimes works well in a fringe location that is not urban.

When people remove the screen from behind a CM 4228 antenna, they actually take away the reflector - usually to try to receive two signals from two different directions without turning the antenna.

If if works, all is well and good. If it creates more problems then it solves, then the people jump on the internet - explaining that they have a problem and are looking for a solution.

The solution - which they usually do not want to hear is to put the screen back up and use a antenna rotor to properly orientate the antenna towards the strongest part of the signal.

In this op's case, he might want to turn the antenna away from the strongest part of the signal and loose some of his gain to reduce the amount of signal going to his tuner.

One other thing he might need to do is connect his antenna wire to a 5 way splitter, which would have enough loss built into the splitter to loose a significant part of the signal to reduce the amount of signal coming in.

hey guys,

great info. here....wow.

so pulling off the amplifier got rid of the audio dropouts, but now, the receiver gives me the "signal loss" message on every channel every 10 minutes or so. I am getting 84+ signal strength on each of the OTA channels.

so, I can certainly return the 360 antenna back to Radio Shack.

sounds like I need a directional antenna mounted on the top of my house, which I was hoping to avoid(it's a pretty steeply pitched roof), but the OTA HD channels look so pristine, I think I am going to have to give it a try!

I wouldn't go directional; I'd still get a 2-bay bowtie. My geographical situation isn't that different from yours, and mine works great. I don't have any VHF channels anymore, but even when I did, the analog picture on my 2-bay was VERY good.

I use an Eagle Aspen DTV2B-UHF that I paid less than $20 for shipped (SummitSource.com). It's similar to an Antennas Direct or Terrestrial Digital dB2, or a Channel Master CM-4220, or a Winegard HD-1080. They're cheap, compact, and rugged, and have a very broad beam width. If you're not inside a commercial district, it should work for you, too.