Signal Question

[kman]

I have a Sony XBR800 receiving OTA signals on a Radio Shack bowtie indoors.  720p and 480i come in absolutely perfect.  Whenever I switch my HD Reciever to 1080i I experience a very faint ghost line which floats across my TV screen.  Hardly noticable, but noticeable with black images.  The support at Sony says its a signal issue.  I've had multiple HD recievers hooked up and I have reason to be that this is the case.  What would be the reasons for it occuring?

[Pat]

An "issue" with a signal can cover a multitude of possibilities.  But if you're receiving a digital broadcast at the time, a defect as you described would not be typical.  If you're receiving an analog signal, such defects are common.

[kman]

What could be the possibilities?  I hope not the tv.  Very novice to HDTV, everything I've learned has been from this site and very helpful.

What are the signals being broadcasted OTA?  Would an upconvert to 1080i cause a line ghost.  It just doesn't make sense to me that 780p comes in perfect but 1080i has a small ghost tint line that moves.

[P a u l]

WISN is broadcasting at 720p currently all other stations are at 1080i, I think. I thought I read somewhere that one of the PBS stations is in 480, but not totally sure.

[uplinkguy]

Does the ghost line travel vertically or horizontally across the screen?

Do you only notice it on one station?

Some of the symptoms sounds like a ground-loop hum.  If it is a bar that travels up the screen, this is most likely the case.

It is caused when connected equipment has a ground at a different potential.  This can be caused by the dish having it's own grounding rod or from the cable system.  If the tv and other AV equipment are plugged in using a grounded outlet, they should be tied to the house's water inlet pipe and to at least two grounding rods next to the house near the main electrical box.

The makeup of moisture and material in the ground can change the impedence and cause the two different ground potentials to the incoming power.

An easy way to check if there is a problem in your house is to put all your AV equipment on a ground lifter.  (One of those 3 prong to 2 prong things.)

Or it could be on the station end of things as well.

I noticed on WMSN-Fox 47 DT in Madison had a ground loop hum on their digital signal. (I'm currently not seeing it, maybe it only occurs during network programming.)  Since everthing else at my house appears fine, I've concluded that their new digital gear is on a different power source than their orignal analog signal that they upconvert.
  Nobody else has complained about the Milwaukee or Madison stations having the same problem so this is probably not your problem either.

Or it could be something else.  The changing of your screen formats making a difference does not follow this theory, however.

Hopefully this helps eliminate a possibility or solves the problem.
If it is a grounding problem, Gregg Lengling of the group is an expert dealing with grounding issues.


Good luck,
Andy

[kman]

Thanks for the help Andy.

The line moves from left to right, not up and down.  It only occurs on 1080i.  I have no cable or outdoor attenna hooked up to the tv.  
Would this make sense?  I hooked up a 10db Attenuator to the tv and it seems that the line became fainter on the 1080i setting.  It's perfect but not quite perfect.  UGH.

My big thing is that I hope its not a tv issue.  I have no desire to get the thing serviced from Sony's manufacturers warranty.  I had a RCA 38310 which gave me nothing but problems so I returned it.  As a result, I coughed up the cash for the Sony with only their built in svc contract and a separate reciever.  

I currently keep the set on 780p for OTA which is still breathtaking.  I have too many trees for satilite.  I may have to wait until Time Warner gets their act together on their set top boxes and pricing to see if it is a signal issue.

[MesaV]

The following is from http://www.panamax.com/support/faq.asp  , scroll down to the FAQS – Technical section.

Q. What is proper grounding? For my house? Signal protection?
A. Grounding is a very involved subject matter, always refer to NEC (National Electrical Code) or CEC (Canadian Electrical Code) for specific information, but the short of it is you need to create a COMMON GROUND! First the AC has to be properly grounded upon entry to the building.  All signal wires that are to be grounded as they enter a building (per applicable code) need to be bonded to this point. Thus, the coaxial cable sheath entering the building needs to be bonded to this point. Your telephone line should be run through a primary gas tube or carbon block protector and the ground wire from this needs to be bonded to the house ground. Antenna masts, DSS dishes, C/KU band dishes are no longer an exemptions to this rule. They all need to be grounded, and bonded to the same common ground location: the building ground electrode.
 
Q. What is a ground loop and what is ground hum?
A. A ground loop occurs when a piece of equipment or a system is connected to different grounds (e.g. AC and coax or data lines). When the data lines, coax lines or AC lines are not connected to the same grounding point there can be a difference in voltage between them when they enter your electrical equipment.  The differing ground lines are interconnected within the system components. (TVs, Amplifiers, Receivers etc.) Thus, the differences in voltage between them result in small amounts of AC current traveling in a "ground loop" through your equipment. A low voltage "ground loop" appears in your system as interference causing a decrease in performance (known as a "ground hum") in audio/video equipment or horizontal black bands on your TV screen.

[kman]

If it were a grounding issue, wouldn't it show up on all signals?  I'm only having an issue with 1080i.  I have tried just having the TV and Reviever on the same surge protector, again the faint imagee/line rolls along the tv vertically when I upconvert to 1080i.

Also the line is going across vertically on all channels when on 1080i.

I know this is an equipment question here, but how does HD emit a picture?  Could it be a tv issue from going from 720 lines to 1080 lines?  Or a separate signal interference outside of the tv when going from 720 lines to 1080?

I don't want to have a repairman look at it unless its the tv.  If I'm confident it's not the tv, I can live with a 780p picture without knowing where the interference is coming from.  

Thanks for the input thus far, it is very appreciated.

[uplinkguy]

It doesn't sound like a grounding issue. In my experiences, the line always floats from the bottom to the top.

Only other thing I can think of:

Does it happen on all your component inputs?  I'm guessing your model has at least two.


andy

[kman]

Thanks for you help and input Andy.

I don't think it was a grounding issue either.  However, I couldn't figure out the problem and my girlfriend couldn't understand why I had a big ticket tv and was messing around with an antenna.  

I found an alternative solution to my problem.  I returned my HD Reciever to the store and purchased Time Warner Cable.

It was installed today.  The picture is absolutely perfect in HD from the cable fee, no waving line.   Hopefully Time Warner will pickup CBS and Fox soon.

Maybe one day I'll figure it out, but I was really tired of the headache.