TV

[kostello]

not really sure which folder this should go in???


my tv aerial is in the loft and it works fine.

apart from when i'm watching channel 4. it stars out fine then after about 10 minutes the picture goes a little fuzzy and the sound crackles.

the other stations are not affected.

any ideas anyone???

thanks


sa?a

 

[JohnD]

If they knew they would have answered. Perhaps you are in weak area for Channel 4. You could try moving the aerial an inch to the right followed by two inches to the left, or you could try buying a bigger aerial (they are very cheap).

 

[RF Lighting]

Poor connection maybe?

Try fitting a booster.

 

[tockworth]

If your other 3/4 channels are clear there is a possibility that you may have the tv mistuned, and you have are picking up another channel 4 from a weaker transmitter. Check this first put your channel 4 into manual sweep and go through the tuning band on your tv uhf 21 - 69 to see if a stronger channel 4 apears. If it does restore this on your channel 4 button. If this is not the case you could check for continuity through the aerial by connecting an ohm meter between the inner and outer conductor of the co-ax cable it should read a few ohms if it reads open the the cable is fractured somewhere along the line and this would lead to reduced/low signal strength to your tv.(This is a extremely common fault but is more likely to happen to outdoor aerials).The above test will not work if your aerial is connected via a co-ax socket outlet box as it is capacitivly coupled to the cable and will not read through a dc ohmic continuity check.

 

[kostello]

thanks for the pointers

ive already checked for a stronger signal on the stations.

i'll check the resistance later.

it just seem sreally odd to me that the same thing doesn't happen on any of the other stations?!

 

[tockworth]

There is a further possibility and that is you could actually get the same effect if your signal is too strong and overloads your tv to prove this your other tv stations would be of excellent quality ie no trace of snowy pics on any other channel and your channel 4 just to strong and goes over the threshold.Your tv has a circuit in it called agc (automatic gain control) the job of this circuit is to slice the incoming signal down to a level the tv requires.This circuit has limitations and if your incoming signal is too large it simply will not cope.You can prove this by simply unpluging your aerial lead from your tv and holding the plug an inch or two away from the aerial socket,now if you still have a reasonable picture on the screen it is a good indicator that this could be the problem and the signal is just too strong in your area. If this is the case you can get small components called attenuators from any good diy/electrical store of various stengths 6db 12db 18db which simply plugs into your aerial plug then into the tv which will cut down your signal by varying degrees.

 

[kostello]

thanks for the help.

i'm not entirely sure what i've done but it's sorted its self out.

i must have had a bad connection.

thanks again

 

[JohnD]

Weather.