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Coaxial cables?

jenic

Prominent Member
My freeview box will only work if connected to the aerial with new digital coaxial cable, the coaxial that came with the house about 27 years ago which is brown will not transmit a digital signal.

Is there any difference between digital and old coaxial cable or is my cable haunted.

Thanks
 

Chris Muriel

Distinguished Member
The old cable could have deteriorated somewhat for a number of reasons - mositure/humidity could have oxidised the copper at the connectors, it may have had water in it at some time etc. e.tc.
Additionally it may have been a higher loss (attenuation) cable at UHF than the old one in the first place.
Try reterminating the ends with freshly deoxidised connections.

Chris Muriel, Manchester
 

davehk

Established Member
ipod crazy said:
My freeview box will only work if connected to the aerial with new digital coaxial cable, the coaxial that came with the house about 27 years ago which is brown will not transmit a digital signal.

Is there any difference between digital and old coaxial cable or is my cable haunted.

Thanks
There is nothing digital about the freeview RF signal. It's an analogue signal modulated to carry digital information.

And there is no such thing as digital coax either. There are different grades of coax which have different analogue characterisics that suit different uses, frequencies etc. But DTT is no different from normal analogue TV in this respect - the same channel ranges are used and all you need is an appropriate aerial for the channel group in your region and a standard TV coax downlead:

http://www.dtg.org.uk/retailer/tx_lse.html
 

vex

Prominent Member
The term 'digital coax' is used to describe CAI approved coax. It generally has a significantly improved braid and shielding over the traditional contractors 'brown' coax.

This is protect it from interference and co-channel interference and the like.

It could also be (as has been said) just down to a poor connection, maybe down to a stray braid cable shorting onto the centre conductor.

chris
 

pjclark1

Prominent Member
vex said:
This is protect it from interference and co-channel interference and the like.

This does not really affect digital transmissions.
 

LV426

Administrator
Staff member
pjclark1 said:
This does not really affect digital transmissions.
Oh yes it does! It doesn't affect picture quality, but given enough interference, the bit error rate will shoot up beyond what's safe and glitches or "no signal" is the result.
 

jenic

Prominent Member
Thanks for all the advice, i have just used new white 'digital' wire and run it from the aerial to the dining room where there is already cable laid to the living room what we used to use to feed sky onto a second TV, all the wire used is the so called 'digital' and it is all working perfect.

The wire is hidden with my Cat 5 network cableing so i will just leave it as it is now.

Thanks again
 

davehk

Established Member
vex said:
The term 'digital coax' is used to describe CAI approved coax. It generally has a significantly improved braid and shielding over the traditional contractors 'brown' coax.

This is protect it from interference and co-channel interference and the like.

chris

yes, but "digital coax" is an imprecise term. RNE678/100-04 & BS EN50117-1 are more precise ways of referring to it.
 

pjclark1

Prominent Member
LV426 said:
Oh yes it does! It doesn't affect picture quality, but given enough interference, the bit error rate will shoot up beyond what's safe and glitches or "no signal" is the result.

In theory you are right, I agree.
In practice any cable that gives you a "watchable" analogue picture, will give you a working digital picture. I personally, have never found any coax cable that passes an analogue but fails for a digital (assuming you get both signals at the aerial) The level of interference needed to destroy a digital signal going through a coax cable is way beyond anything needed to make an analogue transmission unwatchable IMHO.

LV426
If you have actually seen a case where analogue works and digital didn't down the same coax cable I would be pleased to hear about it.
 

vex

Prominent Member
The bigger problem is that the receive level specs for Digiatal from the CAI is about 10dB below the level specified for analogue. So interference has far more impact on digital than on analogue.

Also in my professional experience, people are far more prepared to but up with poor analogue than a digital picture that goes blocky and freezes.
 

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