722 OTA Problem, Please Help

[ryanker]

I had my nieghbor's house pre-wired for OTA to two Dish 722's. However, when the installers came, they did not use the direct path from the antenna, they added diplexers. One of the 722's get's decent OTA HD channels and the other does not.

In an attempt to troubleshoot, we ran a direct line from the antenna to the 722 with good reception. When we plug this in, we get no OTA signal at all, but the signal returns when we plug the antenna back into the diplexer.

Any suggestions would be appreciated.

 

[TNGTony]

It sounds counterintuitive, I know, but the problem is likely "too much" signal. Digital TV is funky. If you have any type of multi-path (ghosting) you get NOTHING. My guess is the diplexer is cutting signal down just enough to eliminate enough of the multipath signal to allow the tuner to actually decode the OTA signal. On the second 722, the signal may be strong enough that you are getting nothing. I have one station where I get a 100% signal. But that goes to zero if the trees are bloing around pretty good. With an old TV the signal would have shifted slightly and shown ghosts. Instead I get 100% one second, zero signal the next. I fixed it by making my reception WORSE. I now get an 80% signal most of the time and very little problems with cutting out. It's the nature of digital OTA.

A way to check is to hook up a STANDARD tv or tuner to the 722 that doesn't get OTA and see if the TV receives a UHF station. If it does, does it have ghosting? Take care of the ghosting (even if it means putting in a signal atteuator), and plug in to the 722 and you will be okay.

It could be something else, but that is my first guess.

See ya
Tony

 

[ryanker]

Tony,

Thank you for the reply. I ordered a signal attenuator to see if that helps. The bulk of the stations are between 5 and 10 miles away, and I'm wondering if ghosting is a problem. Is it possible that the stack of diplexers and splitters used by the dish installers is enough to eliminate the ghosting. Also, the next house over has a stainless chimney of some sort, and I didn't know if that could also have some effect. Would an attenuator be able to reduce ghosting as well?

 

[osu1991]

I had the same problem with my sisters house this weekend. I prewired the entire house and she is only 5 miles from the towers now. Put up the antenna in the attic, trace which cable is live in the media cabinet and go to scan channels on the receivers and get nothing on some channels and others right at 100%. Drove me batty for an hour until it dawned on me that I might be over-driving the tuners. Added a 10db attenuator in the media cabinet and bam all the channels popped in at 88 to 90%.

 

[TNGTony]

Tony,

Would an attenuator be able to reduce ghosting as well?

The attenuator will essentially make both the main signal and the multipath (ghost) weaker. Since the ghosts are generally much weaker than the direct signal, it should drop the multipath signal below the threshold where it kills the reception of the signal all together.

See ya
Tony