8890 TV tuner feedback

I have the TV tuner without any issues dude. If this is your second 8890 then I would say there is something else causing the feedback rather than the laptop. Have you tried using the laptop from batteries with nothing else attached except the TV aerial?

If you disconnect the TV aerial but leave the TV program running do you still get the same feedback (obviously the main sound will only be white noise but the feedback may still be present).

Also which version of the TV software are you using (4.24 is the latest and works properly with hyperthreading)?

Basically need more info before we can come up with any other ideas.
System config, ext. speakers, ext sound card?

You should also check that the mic is turned off. There is a builtin mic at the bottom of the screen just to the left of the three LEDs.

Hmm. So if you ran on battery the feedback went away?
As to picture quality you definitely need a good aerial. I am using a pair of rabbit ears with an amp but because we are in such a bad reception area I can only get UHF semi-clearly. If I hook up to the main house aerial the signal comes thru really well.

I don't understand why the ac adaptor is producing feedback because it only has DC volts coming out of it. The only thing it could be is being poorly grounded or poor filtering (although I have both available AC adaptor types and both work without any feedback) - strange.

The other thing that was not clear - did the feedback go away when you muted aux?

on the lower cable channels, have you adjusted the capture frequency? By that I mean have you opened the TV control panel and selected the "Spanner" (setup) icon. Under each channel you can fine tune the frequency that the card works with. I have found with my poor signal strength I can improve them slightly if I drop between -5 and -15 kHz from the center frequency.

As to your feedback I just don't know. It sounds like it is interference (ie. hum) rather than feedback (feedback is normally caused by the mic picking up the sound then reamplifying it back to the speakers, whereas hum is a consistent low level noise). What is happening is that an AC signal is being impressed on the DC volts coming out of the AC adaptor. Normally these signals are blocked by the ferrite cores that are located near the ends of the DC power cable (the bulge in the cable about an inch behind the DC power plug). My only other question is have you changed AC power adaptors. Maybe the one you have is faulty.

Bingo!
Now I know what is going on.
You have what is called a ground loop.
What that means is the ground of your AC adaptor is not the same ground as that of your cable aerial. Because they are at different potentials, current flows from the higher to lower and your laptop just happens to be the path between them.

I bet if you have a tv set and you don't notice it it is because your tv set is double insulated (ie does not have a ground pin on its AC power cable).

This is not a laptop problem. It is an electrical wiring problem. What you have to do is to find out how your cable tv setup is earthed.

A word of caution here - you are dealing with high voltages and currents in the AC power lines. These can be leathal and can kill you. If you are not familiar with power wiring I would strongly suggest you get an trained expert to fix the problem. So what I am about to tell you is a guide only.

Ultimately you need to ensure that the ground for your house power wiring (ie the AC outlets), your cable tv power and your cable tv aerial all have the same earth potential. Normally AC house wiring is earthed thru what is called an earth wire. This is a metal stake placed somewhere into the earth close to your house and the earth wiring from the house is connected to this metal stake. Sometimes due to dry weather or poor connections this earth wire can become less than conductive.

Even with a correctly working earth wire sometime poor house wiring will mean that the earth that one appliance gets (say your laptop's AC adaptor) and another on a different circuit (say your cable tv power) are at different potentials. This causes a ground loop.

With aerials - particularly large ones they too can be improperly earthed. You may find that part of your poor signal reception is due to an improperly or poorly earthed aerial setup. I would get it checked by a competent technician (a lot of cable/satellite guys are just wire jockeys unfortunately). If the ground for the aerial is different to that of your AC power line then it too will cause ground loops and this is heard as hum thru your audio system.

Well at least you now know what the problem is. I thought my technical knowledge was slipping there for a minute.

I hope this helps resolve your problem.

At least you will not be blaming your 8790 when it arrives .