Extend tv coaxial cable and dropping signal
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Extend tv coaxial cable and dropping signal

by adburns » Sun Sep 18, 2022 7:07 pm

I recently moved into a property and the TV aerial socket is in a different room from where we want it.

Currently I am running a 15m coaxial cable through the house to the tv in a different room.

After researching, I have bought 25m of external coaxial cable which I plan connect to the existing aerial cable outside and run it around the house to the other room.

Before I start drilling I decided to test the cable to see if carries the signal ok.

This is where I have a problem. I can't seem to get a signal when connecting it to the old coaxial cable.

To test, I took a foot of the new cable and tested it and it worked, hence why I wonder if the cable is too long.

After testing , I can only assume that the 25m is too long and the signal is too weak. Does this sound right?

The only thing I can't understand is that I am already using a 15m cable and that the carries the signal without a problem. Would an extra 10m really cause a problem?


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Re: Extend tv coaxial cable and dropping signal

by ericmark » Mon Sep 19, 2022 1:21 pm

Oh what a tangled web you weave. Not easy working with RF, we come into the realm of balanced feeders, wave lengths, and most which use to take 12 weeks of night classes to get the amateur radio licence.

Never worked it out for TV, but too short of a cable can cause problems, I have seen with amateur radio where cutting the cable two inches shorter can have marked effect on the signal.

Even the way the cable is terminated in a wall socket can affect the signal, and use of by-pass filters can mean testing with DC shows open circuit, but using a wave meter you have an A1 signal.

So to basics, we have the aerial, then some form of braid breaker to stop atmospheric voltages travelling down the cable to give you a shock, this may be the wall plate, or can be a mast head pre-amp, with latter important the wall plate has no filters in it as DC required to work mast head pre-amp.

If it goes into the loft you may have a combiner that combines the signal from TV, DAB, and FM radio together, and at the room a splitter, this may also include satellite signals. So could combine 5 signals then split them again, it gets complex.

In the old days my TV went to living room then back to loft together with satellite and video recorder so I could watch the video after retiring, but as we went from 14" to 28" TV's in the bedroom the quality was some what lacking.

Today the hybrid LNB on my dish sends two signals to my Sky Q and there are 4 signals to rooms direct, I have abandoned terrestrial TV as rubbish in this area Moel-y-Sant transmitter and use stand alone Icecrypt STC3250CCIHD receiver in my bedroom and have 3 wifi Sky boxes in other rooms, not that good, must complain to Sky.

But your best signal strength meter is likely your TV, most have the option to show quality and strength, you want the cable as short as you can get it, and with as few joins as you can. Non is ideal.

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