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TV- distorted HD images

I have a unique problem which no Electrician or Audiovisual / Computer technician has been able to resolve. The problem is distorted images and interference with HDTV signal and Electric appliances. When appliances like: Dishwasher, Microwave, Treadmill are turned on, the TV’s in the house receive distorted HD images and dashes.
My house is about 14 year old.
Configuration: I have cable TV booster going into a 8 way splitter ( Howard 1000MHz ) the splitter sends signal to the TV’s receiving HD signals.
The TV’s receive signal through coax cabling wired all over the house.
All appliances ( dishwasher – Treadmill - Microwave ) are on a different circuits.
Problem: When appliances like: Dishwasher, Microwave, Treadmill are turned on, all TV’s in the house start receiving distorted images and dashes.
Electrician checked out the voltage and circuit board, electrical panel. Looked all ok to the electrician.
Network IT – Tried different booster, Splitter, cable ends.
Line conditioner on the treadmill did not work.

Problem still persists. Everyone has given up.

Please help.

Re: TV- distorted HD images

Have you tried to bypass the booster and splitter? You may want to try to have the booster hooked up,and just try 1 TV at a time to see if you have the same issues. If no go,bypass the booster with all the TV's hooked up. IOW,try to narrow down/isolate the problem.

Re: TV- distorted HD images

Are you using DMI cables?

If using co-ax even standard sattelite TV must have 1 GHZ with high quality connectors or the picture will be blurred.

Re: TV- distorted HD images

Make sure that everything is properly grounded together All grounds need to be at the same potential. They should all come together at your electrical service panel. Often the cable ground is tacked onto whatever was convenient (like a water pipe) and a differential current is generated as the signal passes. Contrary to commonly held belief, the outer sheath on coax does conduct signal even if it is at ground potential- it is not just a covering to shield from outside interference. I'd also take a close look at all the cable connections up to where they enter the last distribution component. To further diagnose, remove the coax from half the monitior/TV's and see what happens. If it's the same then do the other half similarly. If a 'fix' is encountered doing this, plug one more in at a time to determine which one is the problem. Another thing that may help is to create common-mode chokes in all interconnecting coax cables. This is simply making a 6+ loop coil with the coax about a foot in diameter holding it together with ty-wraps. Try to make the loops lay beside each other as crossed wires here negate the choking effect. It is also helpful to be sure that the coax does not closely parallel any other wiring (including other coax). A couple inches should be enough. Finally you may want to try an isolation transformer to any powered distribution components (like the amp). An old-fashioned TV repairman is the source for that oddity, they may even loan or rent you one for testing; it's plug-and-play and physically removes the device plugged in from the supply while allowing current to pass. Isolation transformers are to be used singly- one for each plug; with more than one thing plugged in you lose the isolation effect.

Very few Cable Techs have much understanding of what they are dealing with. TV signals- digital and analog- happen at radio frequencies and simply bending the coax too sharply changes it's RF impedence and capacitance which can cause an out-of-spec interference situation. To fully understand how coax behaves coax takes a small volume-sized book and the cable guy has about 0.001 % of that knowledge. If all else fails find a local Ham Radio operator and see if they can help or know another Ham that can, as what you're dealing with is the life-blood of what we do for fun. Sadly many of today's Hams are not very technically minded, but the old-timers have seen just about everything and if they can't find a fix then nothing is broken- we love any radio-related challenge!


Re: TV- distorted HD images

Thank you all for your feedback and help. Shall try the pointers and inform.
In the meantime, I plugged the cable booster into a 50 foot and plugged it into a power outlet in a different room.
With this my distortion has reduced. Do you think it is the power outlet or the 50 ft cable grounding the signal?

Re: TV- distorted HD images

It may be 'dirty power'- electrical interference from something else plugged into the original circuit. Motors, battery chargers, and touch-lamps are notorious for causing that, as are some other electronics. Try the 50 ft cord in another outlet or two as far away as it reaches from the original outlet- you're likely to be on a different circuit that way. If that clears it up then a computer-type "Power Conditioner" may work with the original outlet. If that doesn't help much, then go around the house and unplug anything that has a battery in it which plugs in- laptops, cell-phones, anything rechargable. Then go for anything with an electric motor. If you find an item that is causing the problem you might be able to relocate it to another circuit.

Let us know how it goes!


Re: TV- distorted HD images

Coax cable, because it is grounded at each end, does not shield the signal as much as people are led to believe. The first thing to do is to put your inline amplifier as close to where the cable enters your house as possible. The stronger the signal on the line, the less it is influenced by EMI from other sources. You can get line powered amplifiers that you can locate where the cable comes into your house and power it through the coaxial cable from another point in the house.

There are splitters that will also pass this power through so make sure if you use this type of amp, that you have a compatible splitter and that if only one port is a pass through, that you use that port for the power supply. By boosting the signal as soon as possible, the EMI will have less effect.

Re: TV- distorted HD images

Is it possible that it could be a single device (TV, Modem) being effected and "back feeding" the signal through the coax?

Re: TV- distorted HD images

My first test would be to bypass the splitter. Split 8 ways, you are reducing the signal by 14.7 dB. Since decibels (dB) are on a logarithmic scale, the signal after the splitter is about 1/30th (or about 3.4%) as strong as before the splitter. This is true whether you have one thing plugged into the splitter or eight things plugged in. (Trust me on the math on this one.)

Also, make sure every coax connection is tight.

Re: TV- distorted HD images

In giving this some second thoughts, I now see two problems. First, you have the wrong type splitter. Your splitter is for broadcast signals, not satellite or cable. This is the splitter you should be using.


Second has to do with using an amplifier before the splitter. I take back the advice I gave earlier. Using an amplifier at this point on a cable will overdrive the signal, unless you get a real high dollar amp the will limit the output so that it doesn't get overdriven, but a cable signal is normally near the 100% limit at the entry point, so an amp is not necessary.

This would really solve your issues though, it is an eight way splitter amp. Each port get a 4dB boost, that should not overdrive the signal. It also has a 22 dB port to port isolation and can be used with your cable internet.


BTW, the solid signal web site is a very good resource for all things related to antennas, cable structuring, etc. They have a very good forum if you need answers to really difficult issues. They are to TV reception what crutchfield dot com is to home and car stereo systems.

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