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Old 23-08-2007, 16:46
lfcevans
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Is it ok to connect 2 coax cables to one aerial without loss of signal. I have a loft mounted aerial and can receive a good signal from it upstairs, but, I want to reconnect the main cable to the aerial so my new (Coming monday) intergrated TV can pick up freeview from the original coax wall socket.
Is there a way of doing this ??
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Old 23-08-2007, 16:58
Cruachan
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I think that what you need is a distribution amplifier which takes the signal from the aerial as its input and provides outputs for a number of TVs.

Here is one such ...

http://www.maplin.co.uk/Free_UK_Deli...fier_29413.htm

You'll see that that one provides 6 outputs - you'll be able to come across ones with two outputs upwards.

But ... are you receiving a good enough signal for Freeview? If not there will be further work to do.
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Old 23-08-2007, 17:12
chrisjr
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You will seriously screw up the signal to both TVs if you simply twist the wires from two or more coax leads together and stuff them into the terminals of the aerial. there are three options to do this properly.

In a strong signal area use a passive splitter. You can get metal bodied types with F connectors which do a better job than the very nasty white plastic types. But you will get some signal loss through these splitters which could kill a weak digital signal.

In marginal or poor signal areas you need a powered splitter of some kind.

If there is no mains supply in the loft use a masthead amplifier with multiple outputs. They are normally designed for outside use but will work OK in a loft. You will need to install a power supply near one of the TVs to send power up the lead to the amplifier however.

If there is a mains socket in the loft you can install an indoor amplifier to do the job.
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Old 23-08-2007, 21:04
Sam Radford.
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These diagrams are what you need:
http://www.satcure.com/tech/amps.htm#masthead
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Old 25-08-2007, 20:03
lfcevans
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Thanks for the help.

Because of my wife now wanting me to move the position of the TV to the other side of the room soon, It`s given me the push I need to put a new shielded cable from the attic down the outside wall and just feed it in to the new position. But while I wait for the order to move it all, as a temporary measure, I`ve connected an old anolugue aerial to the old coax for the wall plate, and pointed it in the direction of the local mast. Using that, its picked up 32 channels, but what I want really is the mux that sky sports news is on because I dont subscribe to that on Sky. Does anybody know which one its on.
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Old 25-08-2007, 20:20
SimonBlackham
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You need to post which transmitter you recieve from - or the first part of your postcode - or put your postcode into the Wolfbane 'predictor' for more info.

Sky programmes are on MUX-C - Sky News is LCN 82 and Sky Sports News is 83.
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Old 26-08-2007, 16:13
lfcevans
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Thanks again for the help
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Old 26-08-2007, 17:11
mrfreeview
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Is it ok to connect 2 coax cables to one aerial without loss of signal. I have a loft mounted aerial and can receive a good signal from it upstairs, but, I want to reconnect the main cable to the aerial so my new (Coming monday) intergrated TV can pick up freeview from the original coax wall socket.
Is there a way of doing this ??
If your signal is as good as you believe then all you actually need is something like this http://www.screwfix.com/app/sfd/cat/...44540&id=63654
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Old 09-01-2008, 19:30
icsys
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You will seriously screw up the signal to both TVs if you simply twist the wires from two or more coax leads together and stuff them into the terminals of the aerial. there are three options to do this properly.

In a strong signal area use a passive splitter. You can get metal bodied types with F connectors which do a better job than the very nasty white plastic types. But you will get some signal loss through these splitters which could kill a weak digital signal.
I know this is an old thread but...

That is exactly what I have done... two coax from one aerial.
Perfect reception on both tv's.

Introducing a splitter into the coax willl reduce the signal strength to each tv by 50% Not too much of a concern in a strong siganal area.

Using an amplified splitter serves only to amplify unwanted interference. If the digital signal is weak there is no substitute for a masthead amplifier.
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Old 09-01-2008, 20:22
SteveMcK
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I know this is an old thread but...

That is exactly what I have done... two coax from one aerial.
Perfect reception on both tv's.

Introducing a splitter into the coax willl reduce the signal strength to each tv by 50% Not too much of a concern in a strong siganal area.

Using an amplified splitter serves only to amplify unwanted interference. If the digital signal is weak there is no substitute for a masthead amplifier.
Just stuffing two cables into one aerial will reduce the signal strength by at least 50% on each and probably more due to the impedance mismatch. It will also affect some channels more than others. If you're in a strong signal area it'll probably work, but it is poor practice.
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Old 09-01-2008, 21:29
mrfreeview
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I know this is an old thread but...

That is exactly what I have done... two coax from one aerial.
Perfect reception on both tv's.

Introducing a splitter into the coax willl reduce the signal strength to each tv by 50% Not too much of a concern in a strong siganal area.

Using an amplified splitter serves only to amplify unwanted interference. If the digital signal is weak there is no substitute for a masthead amplifier.
All Good Engineering practice and electrical theory out of the window on this one then!
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Old 09-01-2008, 21:41
Mark.
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Using an amplified splitter serves only to amplify unwanted interference.
Not if it's close enough to the aerial.
If the digital signal is weak there is no substitute for a masthead amplifier.
And, of course, a multi-output masthead amplifier is nothing like an amplified splitter...
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Old 09-01-2008, 22:46
SimonBlackham
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If you are putting in a new downlead - put in two instead and do what we have done.

There is a 4way distribution amp behind the TV fed as shown in the 'Services' box to the left - with extra leads through to the kitchen and back upstairs to the bedroom.

LP is an amplified log-periodic aerial
= are 10 to 20m of Aerial Co-Ax using 'F' connectors (with adaptors where necessary)
TUTVA is the TopUpTV Anytime box
Astratec is a TopD2 box which has been moved up to the bedroom replacing the DigiLogic (which has gone to my Daughters)
There is a Hard Disk/DVD recorder (analogue) in the aerial
The VCR has been removed (as no longer necessary)
The Matsui is a TOPD2 box in the Kitchen with a 21" HD LCD TV
Son doesn't bother with the Freecom any more.

(I will change the services list to reflect the current situation when it has stabilised)

So the kitchen and bedroom have STBs (Matsui and Astratec TopD2s) which give flawless reception (after going through a few boxes, amplifiers and up to 30m of aerial lead) - unlike the TopUpTV DTR which is now first on the aerial and can be used to feed programmes and recordings to the other TVs using RF. It may seem stupid to feed a programme via RF to a downstream TV that has an STB - but the STBs have different delays on the sound so that it echoes terribly - unless both displays use the same digital source! (actually the Astratec and Matsui have identical delay so were OK when we had one in the lounge and one in the kitchen - but we have lately re-arranged as above and this is no longer so)
I am toying with connecting a video cable (using shielded cat5) to send sound and vision to the kitchen TV in parallel with the Aerial lead to get over this sound echo problem.
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Old 13-01-2008, 20:23
Cme2007
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Just stuffing two cables into one aerial will reduce the signal strength by at least 50% on each and probably more due to the impedance mismatch. It will also affect some channels more than others. If you're in a strong signal area it'll probably work, but it is poor practice.

Oooooops! Been running like this for a couple of years now.

Should I dismantle it and go back to analogue?

Still, I have always worked to the motto, there's 2 sorts of systems out there, them that work and them that don't.

Now, where did I leave my hat, six-shooter and the horse?
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Old 13-01-2008, 20:59
Mark.
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Oooooops! Been running like this for a couple of years now.

Should I dismantle it and go back to analogue?
No, just remove one cable and put a 2-way masthead amp in instead. Like this (if my ASCII art skills are up to scratch):

Code:
   A   MA  ________01
<<<---- []<_______  O2
A = Aerial
MA = Masthead Amp
01/02 = the two outputs from the amp
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Old 13-01-2008, 21:33
mrfreeview
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No, just remove one cable and put a 2-way masthead amp in instead. Like this (if my ASCII art skills are up to scratch):

Code:
   A   MA  ________01
<<<---- []<_______  O2
A = Aerial
MA = Masthead Amp
01/02 = the two outputs from the amp
Better Still if you have a high enough Signal Strength then fit a 2-way splitter. www.screwfix.com item 63654-90

A simple Passive device so no introduction of noise.
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Old 14-01-2008, 01:46
icsys
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Oooooops! Been running like this for a couple of years now.

Should I dismantle it and go back to analogue?

Still, I have always worked to the motto, there's 2 sorts of systems out there, them that work and them that don't.
Been running like this for about 2 years myself and it works fine for me.

Originally Posted by mrfreeview
All Good Engineering practice and electrical theory out of the window on this one then!
Who cares if Good Engineering practice and electrical theory goes out of the window as long as it works.
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Old 14-01-2008, 09:54
Big-les
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.....
Who cares if Good Engineering practice and electrical theory goes out of the window as long as it works.
Well the next time you go on your holiday flight just hope that someone more professional than you has installed the radios and nav aids!!!
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Old 14-01-2008, 13:28
Justin Aerial
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As a general rule a splitter is to be preferred to an amplifier as it does not introduce any noise, or the possibility of cross modulation interference, the latter could be significant at DSO (Digital Switchover).
But it`s all about the signal strength in your area as to if this is possible without degrading the signal. I`m not a fan of "reception prediction by post code", they`re wrong more often than not.
Working out your signal strength involves a bit of research, this gives you some clues :
http://www.aerialsandtv.com/aerials.html#SignalStrength
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Old 14-01-2008, 15:04
Big-les
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As a general rule a splitter is to be preferred to an amplifier as it does not introduce any noise, or the possibility of cross modulation interference, the latter could be significant at DSO (Digital Switchover).
But it`s all about the signal strength in your area as to if this is possible without degrading the signal. I`m not a fan of "reception prediction by post code", they`re wrong more often than not.
Working out your signal strength involves a bit of research, this gives you some clues :
http://www.aerialsandtv.com/aerials.html#SignalStrength
Yes and Iím sure Wolfbane have some interest in aerial amplifier manufacture.
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Old 14-01-2008, 16:11
Nigel Goodwin
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As a general rule a splitter is to be preferred to an amplifier as it does not introduce any noise, or the possibility of cross modulation interference, the latter could be significant at DSO (Digital Switchover).
I wouldn't consider that a general rule!

If your signal is exceptionally strong, then a passive splitter is fine - but in all cases it reduces signal strength, so reduces your signal to noise ratio.

If the signal is 'weak' enough not to cause cross-modulation of an amplifier, than an amplified splitter will increase your signal to noise ratio, improving things. An amplifier doesn't add noise, or they wouldn't be of any use.

The only factor is how strong the signal is, and cross modulation.
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Old 14-01-2008, 19:18
Channel Hopper
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An amplifier doesn't add noise, or they wouldn't be of any use.

The only factor is how strong the signal is, and cross modulation.
*snort*

and, back to school he goes.


BTW passive splitters with plastic covers, mainly sold by the batch online,will introduce noise into the system by leakage, virtue of proximity to the transmitter,
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Old 15-01-2008, 00:12
mrfreeview
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I wouldn't consider that a general rule!

If your signal is exceptionally strong, then a passive splitter is fine - but in all cases it reduces signal strength, so reduces your signal to noise ratio.
If your signal were -40dBm with a noise value of -150dBm then after a 2 way splitter (assuming no internal losses) the signal level would be -43dBm and the noise would be -153dBm on each of the outputs. .......so how has the signal TO noise ratio been reduced?????
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Old 15-01-2008, 09:47
Nigel Goodwin
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The limiting noise factor at the frequencies in question is the noise of the receiver front end (NOT noise entering the aerial) - so the splitter reduces your signal, the noise (which is after the splitter) isn't reduced - so your signal to noise ratio drops. Also a splitter will introduce some noise of it's own as well.
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Old 15-01-2008, 12:35
tr_ramsgate
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I used to think that it was easy to see if any intervention between the TV and the aerial was increasing or decreasing the signal to noise ratio. All you had to do was to look at the signal quality meter on your STB and see how it changed.

Now, I'm not so sure, after various experiments with weak signals.

First of all I have noticed that even when you have high quality readings you can still get flashes of picture perturbation on digital TV which don't show up on the quality meter.

And, secondly, I have found that direct connection of an aerial can produce a more stable digital picture, even though with an amplifier the meter readings are better.

Even more bizarrely I have seen that the strongest channel with an amplifier isn't the strongest channel without an amplifier. (Tested a few seconds later so wasn't due to a change in the weather.)

Suck it and see seems to be valuable procedure.
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