Is the older non-shielded coax cable adequate for digital freeview?
I've got such a cable running down the wall from the loft to the tv signal socket in the sitting room. The cable was installed when the house was built.
I've got a TFT TV with freeview plugged in and the picture for BBC1 / BBC2 gets a bit pixalated.
Have installed an outside digital aerial with shielded coax as far as the loft where it joins the the non-shielded coax.
Also have a signal booster between the socket and TV.
Builders use the cheapest rubbish they can get away with. It was barely acceptable 20 years ago. It's woefully out of date now.
Things have moved on. Not only the shift to digital TV but all the other signals now flying around. Cables both pick up and radiate signals. Shielding is one tool to help minimise those effects.
Something else to bear in mind is that cable doesn't last forever. For example, the outer jacket goes brittle after prolonged outdoor exposure. Loose cables rub against the building and wear holes in the jacket that let in water. The copper shielding oxidises. This all has a progressively larger effect and so signal losses mount up over time.
Then there's how a cable is pulled and installed. Common problem include tight bends that acts as frequency filters. In effect, they diminish or even stop certain frequencies reaching the TV.
BBC1 and BBC2 are part of the group of national channels that everyone who can receive Freeview must be able to access. To make this happen, the transmitters are set to give the most power to the BBC and ITV channel groups. If you are losing BBC1 & 2 then I'd expect you to see problems on the other channels in that channel collection (MUX). So that would be BBC3 & 4 at the least. This could be down to cable kinks or it might be a combination of the new aerial and the channel allocations on your local transmitter.
You've probably bought a wideband high-gain aerial. They're the most common type sold. You'd be forgiven for thinking that these pick up everything equally well. But in actual fact all aerials are better at some frequencies and worse at others. If you look at the graph below the black line is the response curve of a typical wideband high-gain aerial. You can see that down at channel 21 it picks up far less signal than it does between channels 51 and 68. If you live in a place where local transmitter has BBC1 & 2 down near channel 21 then your aerial might struggle. Putting a booster on near the TV isn't going to help that. The losses will have already occurred in the cable before the signal gets to the booster.
The best things you can do are getting the aerial aligned for maximum signal
quality and then adding a mast-mounted booster/amplifier to help compensate for the cable losses.
To align the aerial, get the help of a friend and use your TV's signal display to check for quality if it has that feature. If not then simple signal strength will have to do. Get on your mobiles. One viewing the TV while the other adjusts the aerial. Bear in mind too that once you have the direction correct then you might find some advantage in adjusting the vertical angle too.
If you can change the old downleads then do it. You'll get more signal at the TV.
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