Picture Quality on Terrestrial Channels
 

I have an analogue STB and I recently had a fault with my cable modem. Since being fixed (splitter was faulty outside) I've had diagonal lines on my TV on channels BBC1+2 Wales, ITV and Channel4, when viewed via the TV tuning not on the cable channel. It doesn't notice much on my Widescreen TV, I think because of the 100Hz refresh rate its got but on portables its unmissable.

The cable modem had a 3.5db attenuator before the engineer came but he took it off but I'm not sure what effect this had on the TV picture because I took it off myself when the modem wasn't synchronising and it didn't seem to affect the TV picture. Would the attentuator only affect the TV signal if the modem was in sync ?

When I rang faults about it the guy said they only guarantee picture quality on the cable channel and not the channels which are received via the carrier signal. I wondered if this was correct, he also said if I asked for someone to come out they would charge me £25 callout charge if they found the cable channel was working fine.

Thing is how am I suppose to watch one channel and record another by just using the cable channel ? The reason I went on cable in the first place was because I could only get 3 english speaking channels.

Thanks.

Re: Picture Quality on Terrestrial Channels
 

This is bypass channels on the cable, for the "ordinary", is it?

Nothing altered on the analog STB?

Any other devices with RF out inline, and on when they were not before - I'm thinking co-channel / image channel interference (image channel is usually 10 channels away, but it can vary with TV design). Lines and patterning are usually some form of channel conflict, but interference can result from excess signal level - any extra amplifiers and splitters?

Re: Picture Quality on Terrestrial Channels
 

Yeah, it's the bypass channels 1-5, not viewed using the STB tuner. I've got a 6 output amplifier connected, I just tried connecting a portable directly to the output of the STB and the picture is totally line free so it looks like my amplifier is causing the interference. Any recommendations for a good quality amp that will last longer than the one I've got, only had mine 5 yrs, it is in the attic though - perhaps temperature extremes shorten their life.

Only thing I don't understand is why it suddenly became worse after the cable modem fault was fixed. I'm sure all the engineer did was change the splitter in the box outside.

Cheers

Re: Picture Quality on Terrestrial Channels
 

Maybe the levels are now too high for the amplifier - perhaps an attenuator between the STB and the amplifier would help.
http://www.maplin.co.uk/Module.aspx?...rldID=&doy=8m2 6 or 12dB though - 1/4 the power (1/2 the voltage) or 1/16 power (1/4 V).
If the signal is driving the amplifer that hard, maybe the 12dB would be needed.

If you have a passive splitter/combiner, try that inline and see if it cleans up.