Radio Shack coax wiring accessories

[lordsmurf]

Anybody have trouble with hum or hiss on their coax lines? Or distortions? I've got some minor issues on one tv set and one capture card. Anybody have experiences with these:

TV/CATV Attenuator

FM Trap

Inline 75W DC Block

Or other suggestions? Advice MUST be for coax, that is what is used.

[redwudz]

What is your signal source? If it's cable TV usually the signal is strong enough to get around most problems. The RS coax is fine as long as you you use the heavier duty foam type with the larger center lead. A DC block is really for blocking voltage on the coax that is used for antenna amplifiers. If you are on a CATV system and you are getting noise, it is almost always a grounding problem. Can be as simple as noise on your electrical grid. If you have two devices plugged into two different outlets in different rooms, this can sometimes introduce noise. A FM trap is only useful if you have a highpower RF transmitter nearby. And only for FM. If you are using an antenna system and distributing it, you can get tuned traps for individual frequencies, but you have to know what the interference is. An attenuator is if you want to reduce signal - not usually the problem.

[lordsmurf]

One is broadcast, the other is coax output from a RCA DRD222RD DirecTV receiver. The noise is present on both. Different rooms, different outlet, different electrical circuits. RG6 cable, best I could find.

I ran a powered $25 coax amp from Walmart at the end of the 100-ft coax sitting in the computer, which then uses a 2-foot coax RG6 from amp to computer. It did clean the picture, though noise was the same either way, so noise not from amp.

I've looked for hardware audio filters, kind of like what a TBC is for video, but nothing has been found, outside of one $1600 device.

I can always buy and take things back to Radio Shack, so if anything there may even remotely help, I'll test it out.

[powaking]

I would check to make sure your Coax cable is grounded correctly. I had an issue with a few TVs and it came out that the cable connector outside was not firmly screwed into the grounding block. Took out the nut that the contactor put in (didn't need the nut there, not sure why he even put it) and was able to firmly tighten the fitting on the grounding block. Make sure your block is grounded to your house ground or cold water pipe somewhere.

Not sure if that will fix your problem but best to start with the obvious.

[redwudz]

Your amp is at the end of the cable? Should be at the start or you will amplify the noise. If you are getting audio noise, that is a different problem. In RF Video signals the sound is FM, fairly immune from interference. The video is AM and you can get interference from external rf. This usually shows up as ghosting (From external TV signals) or herringbone patterns (From various RF sources). Grounding is very important. If you have a newer home, your wiring is probably OK. Older places may have poor connections in the ground system. This will let rf interference into the ground leads. Two keys to reducing interferance are strong signal and good grounding.

[lordsmurf]

There is nowhere to ground any cables. The antenna are rabbit ears, and the water pipes are underground in the foundation or in the bottom of the wall in the bathrooms only. The satellite is half-way grounded to the metal sheath around the fireplace, but that was the best that could be done (useless to be honest, a feable attempt if lightning ever strikes the dish). The house is 35 years old.

The noise is a hum/buzz sound, one I can remove with DartPro on my captures, but it's still annoying, especially on the live tv in the next room. It's not merely the normal hiss you can sometimes pick up on analog sources.

[redwudz]

A few things to try: Check your main breaker box where the power comes in to the building. It will have a ground lead to a ground stake. Make sure that connection is tight. The building is new enough (assume 3 prong outlets) that the wiring is probably OK. You can try a Radio Shack AC line filter (RS15-1111), it might help. Usually the type of audio noise you describe is from florescent lights, electric motors, light dimmers. These will usually be intermittant, though, and easy to check. The incoming AC line from the power company is in two phases. Both together are 220v and individual 110. Some of your outlets are on one side and some on the other. If your TV with the problem is portable enough, you could plug it into the same outlet as your satelite reciever temporarily with the long coax hooked up and see if that helps. Something else that sometimes helps in the case of noise into the computer is to add a UPS (Uninteruptable Power supply); they usually have surge suppression and line filtering built in. Check your dish manual and see if the dish should be grounded. If so, you could purchase a ground rod and run a wire up to the dish. To eliminate really persistant interferance it usually takes some trial and error and juggling of connections.

[lordsmurf]

Yeah, 3 prong outlets.

Breaker box is good. Checked that not too long ago for unrelated incident.

I'll try that filter, thanks for the suggestion.

Hmmm. Well, the only thing is this room, on this breaker, are the 3 outlets for the computers/tv. The other one is a bathroom and that one outlet in the next room (same wall). But I'll look at this more. There is a ceiling fan in the room with the computer, but that's on the next breaker over, connected to the next room (same for light in fan).

All devices in this house are on good surge strips. Checked that for potential errors already, none there.

Dish should be ground better, but nearly impossible to add any other method of wired grounding due to location (and cannot move dish, only clear angle free of trees without taking chainsaw to neighbors yards). Sat is on 4-signal LNB (double with powered sat splitter), and other 3 connection just fine. RCA box tested for problems, just fine.

If you think of anything else let me know. Thanks for the feedback, I've got some tests to run and things to look at.

Appreciate it.

[lgh529]

Here are some thoughts on this. Take them for what they're worth.

A hum/buzz sound is commonly heard on TV sets when the video is over modulated. You can tell if this is going on if the white colors on the video picture are streaking or overly bright. This is acually less likely since the noise is on both the broadcast and the sat receiver.

FM interference is probably not the problem since it usually isn't a constant hum or buzz sound.

I'm betting that there is a ground loop. Since the noise is on both sources, the only common thing that causes buzzing is a grounding problem. Even if there are dimmers and flourescents in the room, a well grounded RF system will reject that noise.

You really don't want to be removing noise with software because that will degrade the quality of the audio. You'll get artifacts in the audio that sound crappy.

I'm with redwudz, connect everything up to the same outlet via extension cords, etc. If that doesn't fix it, take a copper wire and connect all the chassis' together with the shortest length of wire you have (less than 3 feet).