HELP: specific 2.4GHz video xmitter interference, what causes it?

I am going nuts. We are using a 2.4GHz wireless video broadcaster in our home (Germany,

240V, 50Hz, PAL TV 25fps). It is based in the lower level and transmits a satellite receiver output to the upper level TV room, about 25ft away (3x 1ft stone walls in between). The received video signal has a large regular interference, a horizonal stripe (about 5% high, small vertical bands with colored specks, almost white appearance) crawls fast through the picture, accompanied by a chopping noise, about 8-10 chops per second. The stripe scrolls fast through the picture, about 2-3 times per second, downwards. A classical interference. PAL operates at 25cycles per second, German power at 50Hz, what does this tell about the interference spectrum/ freq?

Yes, we have a variety of other wireless devices in the house, including a Fritz! WLAN, 2 2.4GHz phone bases (5 mobile phones), several wireless weather stations, a Razr cell phone. I pulled ALL plugs of all known wireless devices, unscrewed fuses wherever needed, NADA! The noise remains, as strong as before. I even put all wireless phones into a metal box and carried it out of the building, still no change. Meaning that all my wireless devices do NOT have any impact at all, the other noise is the main problem. WHERE THE HELL IS IT COMING FROM?

The received video signal is rather weak, moving the receiver around yields interesting spots of "almost" no noise (about 1ft apart). Interesting to note: the noise gets typically more solid if the overall picture is better and clear/strong. Meaning if I settle for a grainy video, then the stripe is almost invisible (yet noticable in the audio part as the mentioned fast 'chop chop chop' noise)

I am at the end of my wits. Cannot analyze freq sprectrum nor do I have other tools handy to investigate. Am a left handed physicist, not an electrical freak, hence my plead for support here! What could cause this strong interference, a neighbor, the power line, the antenna from the satellite/cable (even switched off the HF amplifier for TV)?

What else should I try to isolate the problem? Cut the power line of all my neighbors?

Thanks a bunch! michael

Reply to
Loading thread data ...

"" wrote in news:7d76831c-f322-4ff0-


Had you ever seen this device work properly anywhere, the one you own ?

Maybe the device is defective.

Reply to

I am pretty sure I did test it with good results (before we moved), but cannot say for sure. Since none of my own devices is causing it I still asume an external noise source, mainly the neighbor's strong WLAN (I can sensek his signal with my own PCs while I can hardly get my own ethernet signals down to the basement). Would need a Faraday cage to test the entire xmitter system in, but don't have any setup to do so. The xmiiter has 4 channels to operate at, all of them show the same interference.

Reply to

To restore balance to the world wrote in

Poor weak signal - do a test move the receiver to the same room as the transmitter (3ft of stone)... Chris

Reply to

You have come to the right place.

Good analysis. The AC power line frequency is 50.0Hz. Twice the vertical sync is not exactly 50Hz, resulting in the "crawling" horizontal bar. What you're seeing is AC power line "interference". My guess(tm) is that you have an AC power supply problem for whatever is running either the receiver or the transmitter. The 8-10 chops per second would be "motorboating" also known as power supply oscillations. That fits. Methinks you have a power supply problem.

It's internally generated in either the transmitter or receiver. The easiest way to test this is by replacing or isolating components. You've already replaced everything electronic in the house. Perhaps it would be best if you isolated the system. Take the transmitter, receiver, and their corresponding power supplies to a completely different location. An RF proof basement is ideal. Try it there. If the "intereference" is still present, you have an internal problem with the devices.

Hmmm... Maybe more than one thing wrong. Weak analog video signals can do odd things. You might have just a little hum, which usually won't be noticeable, but is aggrivated by the weak signal. It could also be something oscillating in the receiver, where AGC is required to keep it stable. Kinda hard to tell.

Ummm... any chance you have positioned either the receiver or the transmitter near some device that has a large 50Hz field? A desk lamp, other wall warts, TV flyback xformer, motors, etc will qualify. If so, move it away from these.

You only have one wit, which hopefully has no ending. I use my wit to produce humor. I suggest you do the same. It sometimes helps with difficult troubleshooting.

Troubleshoot by substitution. Do you have access to another transmitter and receiver pair? If so replace either the transmitter or receiver (and power supplies). Replace one item at a time. Eventually, the culprit will identify itself.

I don't think it's intererence. My guess(tm) is internal power supply issues.

Cutting your neighbors power might result in unexpected consequences, such as a small riot at your front door. It would be a good test, but is politicially unacceptable, unless you can make it look like an accident. Driving your car into a power pole would work, but does tend to be expensive.

Reply to
Jeff Liebermann

I do agree that the signal strength is low, mainly caused by the 3 thick walls and floors.

But I DO have success, sort of: the transmitter allows to select 4 different broadcast channels, and in one (D, the highest?) I noticed that the wide speckled and running bar disappeared. It was replaced by 2 very narrow and absolutely static ones! That was actually good news, as it was a DIFFERENT interference, one I quickly identified as being from my own wireless base station, located in the same room as the 2.4GHz receiver. That one can be unplugged anytime; also I am considering to disable/cut the transmitter or antenna - the base is not actively used, it only serves as a charger for one cordless phone. It produces a very sharp, whitish bar, in synch with the receiver for some reason (overtone or fraction of the xmit frequency I suppose?), no audio interference noticable. I am quite convinced that the other broad noise is indeed from a neighbor's WiFi/WLAN system. What is baffling is that the plentitude of my own wireless devices (with the exception of the one phone base in the same room) have absolutely no impact on the xmitter/receiver signal, and this bastard HAS, from 100ft away, through several 1foot mason walls. What is he using?? Anyways - thanks for the ideas, hints and suggestions, highly appreciated! michael

Reply to
mw210461 Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.