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Author Topic: TV Aerial Cabling.  (Read 4036 times)

tickmike

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TV Aerial Cabling.
« on: December 07, 2009, 10:27:31 PM »

TV Aerial Cabling.

When I built my house the one thing I did not give enough thought to was the wiring of the TV aerial to each room.
What I did was :-
The outside TV and FM aerial has a mast head amp. and the down lead feeds a power supply and splitter box, TV out and FM outputs, then the TV signal is fed in to a six way amplifier slitter box and FM likewise.
The TV and FM outputs are taken around the house the same way .

eg. for the TV aerial :-
From the six outputs these are fed to different parts of the house, each one feeds up to three rooms and each room has two coax sockets to plug a TV if needed (to move TV about the room ).
So we are talking of six coax sockets soldered in parallel on each way of the six way amplifier slitter box.

As we finish off more rooms I have got to change this wiring.
The system worked ok with the strong analog TV signal but with freeview we are having problems.
Some rooms we can only get some of the freeview programs, the is due to all the attenuation in my cabling and joints.
Any ideas please.

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sevenlayermuddle

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Re: TV Aerial Cabling.
« Reply #1 on: December 07, 2009, 10:40:29 PM »

, each one feeds up to three rooms and each room has two coax sockets to plug a TV if needed (to move TV about the room ).

If I've understood right,  that may be your problem.  If you split the line into multiple spurs using passive splitters ('tee pieces') then the broadcast signal reflects off the end of each spur, back into the wiring, which can cause corruptions with a digital signal.  If you look closely at the analogue TVs this may also cause 'ringing', a bold outline to the right hand edge of everything on screen.   Ringing is just like the more familiar 'ghosting', except the ghost is only a fraction of an inch to the side, so is less noticeable.

Fitting terminators to any unused sockets may help as they'll stop the reflections.  But they'll also absorb some of the signal strength, possibly leaving not enough for the digital sets.  Worth a try?

edit: said 'attenuators', meant 'terminators'. 
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tonyappuk

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Re: TV Aerial Cabling.
« Reply #2 on: December 08, 2009, 02:50:23 PM »

I have sent a long and rather rambling message to Tickmike after he emailed me on this subject and it's probably too long to include in full. Suffice to say I fully endorse SLM's recommendations. It is essential to provide isolation between sockets and not feed in parallel. You are likely to have problems if you do with some sockets not providing adequate Freeview signals  due to the tuning effect of the unused stubs to the other sockets. If anyone wants more info I would be happy to provide.
Tony
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sevenlayermuddle

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Re: TV Aerial Cabling.
« Reply #3 on: December 08, 2009, 03:08:49 PM »

Suffice to say I fully endorse SLM's recommendations.
Phew, that was a lucky guess then  :)

Seriously Tony, thanks for helping out.   I'm aware you have some real expertise that can go way beyond my wild ramblings.

- 7(S)LM
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tonyappuk

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Re: TV Aerial Cabling.
« Reply #4 on: December 08, 2009, 04:49:18 PM »

SLM Thank you for the compliment - just happy to help.
Tony
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tickmike

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Re: TV Aerial Cabling.
« Reply #5 on: December 08, 2009, 10:28:41 PM »

Thanks for all the reply's, I've got some mods to make. :)
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I RECOMMEND TRYING PCLinuxOS (www.pclinuxos.com).
I have a set of 6 fixed IP's From my Kcom Business isp.
BT ADSL2 (G992.3) line>HG612 as a Modem, Bridge, WAN Not Bound to LAN1 or 2 >pfSense (Hardware Firewall and routing) > Ethernet LAN, DMZ,WiFI LAN and Spare LAN .
DSLstats LAN2 linked Ethernet

HPsauce

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Re: TV Aerial Cabling.
« Reply #6 on: December 08, 2009, 10:59:14 PM »

I've totally (well almost - see below) eliminated passive splitters and it's improved Freeview no end.
Where possible I've run all sockets back to the distribution amp in the loft. As there are more sockets than outlets I plug in what seems appropriate for likely use in the immediate future.
Where it's not possible I've got a small powered (typically 2 or 3 outlet) local distribution amplifier.

The only exception is that my main amp has a single higher-power (extra 8dB?) output, not sure what for exactly, but I do have a 2-way passive splitter on the end of that.
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tonyappuk

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Re: TV Aerial Cabling.
« Reply #7 on: December 09, 2009, 12:07:32 AM »

During my correspondence with Tickmike he has made an excellent suggestion to avoid problems with parallel feeds. Make your own terminations with coax plugs and mini 75 ohm resistors to plug into the unused sockets. If the feeds are really all parallelled together that will produce double or triple termination but it will reduce the tuning effect of the unused stubs. If a resistive splitter is being used it will fix the problem.
Tony
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