Very Very odd problem
 

I am having an issue and I can not figure out what is going on.

My setup:
Mohu Sky HD on roof down to Mohu power injector (for the built-in amp) in basement, to A/B switch, to distribution amp, to 4-way splitter. I have a 2013 LG TV in the livingroom on the same side of the house as where the line comes in, and a 2013 Sanyo TV, & 2009 Sony TV on the opposite side of the house. All 3 TV's have individual lines from their coax jack to the splitter in the basement.

The Problem:
In my bedroom and den I can pull in VHF-12 perfectly fine with the Sanyo & Sony, or both at the same time. When I turn on my LG however, VHF-12 drops instantly for the Sony & Sanyo when they are tuned into the station. If I turn the LG back off the station will return at a strong signal almost instantly for them!

I originally thought the LG TV being turned on was doing something to the home's coax lines so I unplugged the coax from the LG's livingroom wall jack. HERE IS WHERE IT GETS WEIRD. The problem still occurred even with the LG tv's coax unplugged!

The symptoms were the exact same and I have been able to reproduce this problem consistently for the past two nights. Does anyone have the slightest idea what could be going on? Is the LG TV somehow sending interference not through the coax but through the home's power lines? I have even tried putting it on two different grounded surge protectors. I tried simplifying my setup in the basement and just plugging the Sony directly into the Mohu power injector and still when that LG tv is on VHF-12 drops though the LG is only connected to power at that point.

One thing to note, that if the bedroom / den TV is tuned into most any UHF station the problem does not happen and all TV's receive signals just fine. This only happens when one or both of the far tv's (Sony & Sanyo) are tuned into one of the two UHF stations in my area, 12 & 13. Also worth noting, with only the LG tv on it can not pick up VHF-12 & 13 though the others can just fine (when the LG is off)

Here is my tv fool report but I have a feeling my problem lies someplace else.

Any help you can offer is great!

To isolate the LG Tv even more as the interference generator.

Test by disconnecting the coax at the LG Tv.

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What is the model number of the LG Tv??

It sure sounds as if the LG TV is producing RF interference that affects real CH-12 & CH-13. A bad CFL power supply or bulb???

Good luck finding a TV repair tech with the skill and tools to isolate that type of trouble.

Can the LG TV receive channel 12 or 13?

Already tried the coax. This happens even then when its just plugged into the wall. The tv is a 55LN5600. Bestbuy still sells the thing.

Any way to test this? Or is there a way to eliminate the interference? Any other symptoms I can look out for? Odd it's such an issue with the LG 50ft away from the other two on the opposite side of the house and the mohu all the way up on the roof.

The LG tv can sometimes pull in those if its a clear night but the Sony can do it pretty much regularly with fewer dropouts. I originally thought the Sony just had a better tuner.

@All: Is there a chance of a ground or static problem? Or does sound like its just w/ the LG? I've grounded everything to the best of my knowledge but am running out of ideas. This is such an odd issue I debated even posting at first, didn't want to sound crazy haha.

Any sound bar or external speakers connected to the LG? I had amplified speakers connected to my TV which wiped out weaker VHF stations when turned on. The antenna was on the roof on the other end of the house.

None other than the built-in speakers. No amplifiers or receivers on any tv. The tv does have some sound settings that try to simulate surround so maybe its worth playing around with that.

It is at least comforting to know that you experienced something similar with your amplified speakers. Just odd its only the VHF stations that drop while the UHF signal strengths remain the same.

Interference from electric and electronic sources does happen.

The Mohu antenna and components are suspect of playing a part in the interference situation.

As a Test disconnect all active and passive parts of the Mohu.

And connect a ANT751 antenna at the location of the out door part of the Mohu antenna and connect the ANT751 to the antenna system.

Home Depot and Lowes can have the ANT751 in stock in the store , no matter what the Home Depot and Lowes web sites say.

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I looked up the model number of the LG Tv on the Internet , did not find information about the interference situation.

However , looks like the the LG Tv has , Wi-Fi .

Can the Wi-Fi be switched off , and does that eliminate the interference??

I would ask a repair shop if they have a spectrum analyzer at their disposal. If so, would the offer any assurance that they would have the ability to isolate the source of interference and repair it? How much would they estimate the service to cost?

Until you can pin-point it's source, eliminating the interference is impossible.

If the cost of servicing the LG unit is excessive, then eliminating the TV may be the most cost effective solution... :( :eek:

I thought of that too but the Wifi is already disabled and not connected to my in home network. Perhaps I will grab an ANT751 to try, should be able to return it after.

I was actually thinking of just getting rid of it too. I knew I should have bought the Samsung that day, both were the same price & size. I understand any answer is just a guess but would you think it's a problem with just my LG, or all LG TV's of that same model? I only bought it in September so its still under the manufactures warranty but I know they will laugh at me if I ask them to repair my tv when my only complaint is that it blocks 2 VHF channels.

There is a guy two towns over who is really good at repairing electronics. Perhaps I can ask him for a spectrum analyzer.