VHF interference

I've attached a shot of the interference on RTÉ 1 and 2 on my TV, could anyone explain what causes this?

It consists of diagonal dotted lines which slowly move towards the bottom left of the screen. There's also a vertical dotted line that moves along the screen from left to right.

I'm receiving RTÉ 1 and RTÉ 2 from Mullaghanish on VHF. I tried last year to overhaul my aerial installation and switch it to UHF for this very reason but couldn't due to co-channel interference in my area.

byte

Looks like a weak signal to me. VHF tends to get sparklies when signal is weak.

This is possibly down to either a poor cable connection, particularly braid connection.

Or, the aerial is perhaps damaged. Is the dipole still intact, and not broken anywhere?

watty

Another signal is interfering.
It need not be on similar frequency. Is it on all channels or just one? Tune manually and see does anything appear.

I've even seen too strong UHF signal do this on some VHF tuners.

byrnefm

I've seen that too on VHF from Truskmore, I had always put it down to a poor signal, though interference is possible too. Funny, I've always found it more annoying than snow on UHF, though don't know why!

It happens on both of my VHF channels, RTÉ 1 and 2. The aerial is only a few months old, an Antiference LP7, perfect condition.

My UHF channels are fairly grainy so I doubt they're overloading the VHF tuner. I guess it could be a long cable run since it only occurs on the TV in my bedroom, the main TV is fine.

watty

The PC?

Antenna

Might it be interference from a DVD player or satellite receiver? (the Lidl Comag digital receivers emit a lot of Band 3 interference!)

Try powering these off completely from the mains (not just standby)
(obviously with receiver using terrestrial loopthrough you will have to bypass.)

Is interference still there?

You can improve matters by using metal instead of plastic splitters (if applicable) and using CT100 type cable (copper braid on copper foil for outer) which will keep the interference from nearby devices out

If you are using a masthead amplifier, try a shielded type power supply, as unshielded ones will pickup interference from nearby devices.

byte

Are the cable drops that dodgy brown single screen stuff? If so, that can be the cause.

Is the TV socket wired correctly at the back? Some sparks don't wire these properly

Maybe the flylead from socket to TV is at fault.