Cable interference

[crimsont]

Two problems:

Background setup: WinXP, AMD 1200+, 768RAM, 40G DMA-5, WinTV capture, DISH network satellite receiver

Problem 1: If I use the cable output to connect, I get unwanted interference and wavy lines. Jiggling the cable helps some but it's still not great. Should I get a better shielded cable? I'm using gold plated connectors, but would like a better picture.

Problem 2: To counter the cable issues in problem 1, I decided to go with the composite output. Picture problem is solved and it looks great. However, now the sound is off (I can actually hear it but it's very faint and turning up my comp. speaker produced a lot of hiss). Is there anyway to get sound from the cable input on WinTV and the video from the composite input?

Thanks for any help.

BTW, my plan is to use Virtualdub Huffy codec to capture (720x480, 29.97, MQ sound), encode to mpg with TMPg, and then transfer to DVD+R. Any suggestions to improve this process is appreciated. The WDM/VFW battle stinks. When will virtualdub support WDM natively? Or should I just go ahead and buy showslicker (or whatever it's called).

[Allan55]

Hi,

A 100% shielded cable may help.

I don't believe gold-plated "anything" is worth the money (based on comments from two Electronic Engineers I know).

Ground everything together with short large wires (I use 14 ga). "Everything" includes the "cable" coax-cable. I use an adapter between the cable wire and a 6" length of cable right at the tuner input. The ground wire has a 3/8" full-circle lug on the end which slips over the adapter and is tightened with the adapter's mounting nut. There is a similar ground at the wall outlet over to an electrical box. (Cable and telephone wall outlets are rarely grounded.) I look for less than 1 ohm across the ground.

Allan

Do you have splitters? If so, you may need an amplified splitter to boost the signal. A two-way splitter cuts the signal to less than half that supplied by the cable; a three-way to less than a third, etc. Cascading splitters are even worse -- a two-way after a two-way delivers a lot less than a quarter of the original signal strength.

[patrickm]

another way to get rid of ground loop problems (usually manifested as 60hz hum in audio) is to get two 75-300 ohm matching transformers from radio shack or somewhere, tie the 300 ohm ends together, so that you actually break the ground connection from the cable outlet to the electrical outlet your tv/vcr/computer grounds to.

besides poor grounding, tying grounds of different absolute potentials can also cause interference, as current will flow from one ground to another. usually the power in your house is pretty consistent (and essentially identical when using circuits on the same breaker), but often the cable feed is grounded outside somewhere else.

[crimsont]

Thanks for the tips. I actually went ahead and solved problem #2 rather than address the interference concerns.

Composite output has no interference so I went with that. For audio, I found running the audio out through my stereo receiver first fixed the problem of muffled/quiet sound.