Non-motoring > Analogue TV plus digital aerial Miscellaneous
Thread Author: L'escargot Replies: 18
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New Mon 17 Jan 11 14:50 
 Analogue TV plus digital aerial - L'escargot
A friend has recently had a digital aerial installed and bought a digital TV for use in a different room from her analogue TV. The aerial fitter wired the digital TV direct to the aerial, but installed what he said was an "amplifier" in the cable to the analogue TV. (There appears to be two separate cables coming from the aerial.) The thing which I don't understand is that the amplifier has to be powered up when using the digital TV. How can the amplifier affect the digital TV when it's merely in the cable to the analogue TV? Any ideas? Is perhaps the amplifier something more than just an amplifier?
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New Mon 17 Jan 11 14:54 
 Analogue TV plus digital aerial - Suppose
>> A friend has recently had a digital aerial installed
>>

see Old Navy's post
www.car4play.com/forum/post/index.htm?t=4589&m=99750&v=e
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New Mon 17 Jan 11 14:56 
 Analogue TV plus digital aerial - Tooslow
I'm being cynical but an aerial amplifier is only needed if there is not enough signal. Driving two tvs from one aerial may qualify but if one was not needed before then there should be no need now. Being pedantic, there is no such thing as a "digital aerial". Sorry, but in this case pedantry alerts us to the question of what was the aerial guy up to? Our analogue service went, we didn't need a new aerial. All of the digital switch-over campaign stuff says "you MAY need a new aerial".

I think someone's been had.
John
Last edited by: Tooslow on Mon 17 Jan 11 at 14:57
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New Mon 17 Jan 11 15:07 
 Analogue TV plus digital aerial - Old Navy
We run three TV's and a PVR off our loft aerial, at the moment they will work as analogue or digital TV's as our analogue has not been turned off yet. At switchover I will have to retune the TVs and PVR as some digital channels may change. We have a masthead amplifier which may not be required after switchover as the digital signal transmitted will be boosted. A masthead amplifier is the best type as it boosts the signal at the aerial and not further down the line when it may have picked up interference which would also be boosted by an amplifier near the TV.
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New Mon 17 Jan 11 15:02 
 Analogue TV plus digital aerial - Robbie34
There is no such thing as a digital aerial. The aerial installed is probably a wide band insofar as it covers the analogue as well as the digital frequencies.

There is insufficient detail here about where precisely the leads come from. My guess is that the downlead from the aerial is fed into an amlifier with two outputs: one goes to the digital TV, the other to the analogue set. If the amplifier is not switched on then the signal to the digital set will be attenuated sufficiently to prevent it going to the TV.
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New Mon 17 Jan 11 15:19 
 Analogue TV plus digital aerial - Bigtee
Normally one feed comes off the antenna and splits one to one tv then to other.

The amplifier will boost it's receive signal as some can be lost in the length of coax after the split.

This one seems to take two feeds from the antenna so in practice why it needs the booster is odd.

As i live on top of a hill the Emley moor transmitter is in view i can see it on a nice day and can receive it with indoor antennas, Better to have one antenna per tv but should you have more tv's then your option is the splitter.

Coax is as important as the antenna as much it's more important as water gets between the insulator (plastic covering) and corrodes the screen wire which then breaks leaving you with a snowy picture.

Indoor in loft has better protection.

On my Ham radio gear i replace my coax every 10 years regardless of condition, i wouldn't for a tv as it's only a receiver.
Last edited by: Bigtee on Mon 17 Jan 11 at 15:20
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New Mon 17 Jan 11 15:29 
 Analogue TV plus digital aerial - Stuartli
>>This one seems to take two feeds from the antenna so in practice why it needs the booster is odd>>

Might have used a Y splitter first (which halves the signal strength of each feed) on the TV aerial lead and used an aerial amplifier for the feed to the second set to boost the reduced strength signal.
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New Mon 17 Jan 11 15:35 
 Analogue TV plus digital aerial - Bigtee
Back some twenty eight years ago we had a rotator on the roof with a tv antenna on top and was brill as kids to watch it spin round to Tyne Tees tv as the programs on itv were different to those on Yorkshire and if good films were on we could watch there's.

Of course no need to do this anymore.

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New Mon 17 Jan 11 15:41 
 Analogue TV plus digital aerial - Bromptonaut
Blimey Bigtee that brings back a memory.

As kids a friend lived in Menston on the 'col' between Airedale & Wharfedale. Surrounding terrain meant they had a scrappy picture from Emley but they did have reasonable reception of tyne-tees from, IIRC, Bilsdale.

TTTV showed Joe 90 and one or two other treats denied to Yorkshire folk.
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New Mon 17 Jan 11 15:38 
 Analogue TV plus digital aerial - sherlock47
Are you sure that it is an amplifier? Line of sight - more likely to be an in line attenuator. Likely to have been installed if the signal was strong and the old analogue TV was being overloaded in the RF stage.
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New Mon 17 Jan 11 15:54 
 Analogue TV plus digital aerial - spamcan61
The only scenario that almost makes sense from the original description is if there is one feed from the aerial which then passes through a two output low gain distribution amplifier, one output to the analogue TV, one to the digital. That would need to be powered up irrespective of which TV was in use.

Even then the 'two cables from aerial' bit doesn't fit in...
Last edited by: spamcan61 on Mon 17 Jan 11 at 15:55
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New Mon 17 Jan 11 16:57 
 Analogue TV plus digital aerial - sherlock47
On further reflection I think what they have done is install a remotely powered 2 channel distribution amplifier at the aerial end of the cables. This is then powered 'up' the cable from an inline power unit situated at the location of the analogue tv. In some of these head end amplifiers only one of the outputs can be used to receive the power feed.

Probably done like this as the cable runs for each tv diverge some where near the aerial or in the loft.

Does that make sense now. However if it is line of site to the transmitter I think that somebody has been taken for a £ ride! unless the cable runs are very long. Maybe the fitter just had run out of passive splitters?

Spamcan has beat me to it!
Last edited by: pmh on Mon 17 Jan 11 at 16:59
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New Mon 17 Jan 11 19:08 
 Analogue TV plus digital aerial - spamcan61
>>
>> Does that make sense now. However if it is line of site to the transmitter
>> I think that somebody has been taken for a £ ride! unless the cable runs
>> are very long. Maybe the fitter just had run out of passive splitters?
>>
I'm not sure where the line of sight issue came into the thread, I don't think Mr. Snail mentioned it. I agree that needing any sort of amplification if there is LoS would be unusual.
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New Mon 17 Jan 11 19:23 
 Analogue TV plus digital aerial - sherlock47
Spamcan

'Line of site' was not from the OP. I read the thread (too) quickly, and then jumped to a possible conclusion in my first post, and then, taking my post as gospel, continued under the same misaprehension.

If in doubt read the question! A new acronym? RTFQ (or maybe RTFOP) - can I make it catch on?

But I have just Googled it and apparently RTFQ is already in common use. Maybe I can make my mark with RTFOP!
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New Mon 17 Jan 11 20:26 
 Analogue TV plus digital aerial - L'escargot
>> The only scenario that almost makes sense from the original description is if there is
>> one feed from the aerial which then passes through a two output low gain distribution
>> amplifier, one output to the analogue TV, one to the digital. That would need to
>> be powered up irrespective of which TV was in use.
>>
>> Even then the 'two cables from aerial' bit doesn't fit in...

Two cables come down the chimney from the aerial. One goes direct to the digital TV, and the other goes to the analogue TV via the amplifier. The amplifier need to be powered up for the digital TV to work, even when the analogue TV is switched off. The amplifier is in a cupboard under the analogue TV. I don't understand it either.
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New Mon 17 Jan 11 20:36 
 Analogue TV plus digital aerial - Zero
I would suspect there is a mast head amplifier, and the "box" that needs to be powered is actually providing power up the aerial feed to the mast head amp.


Thats the only scenario that fits.
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New Mon 17 Jan 11 20:37 
 Analogue TV plus digital aerial - sherlock47
Snail

Spamcan and I have both independently explained above. What is it you do not understand from our answers?

And now Zero with the same answer!
Last edited by: pmh on Mon 17 Jan 11 at 20:39
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New Mon 17 Jan 11 20:48 
 Analogue TV plus digital aerial - Zero
opps didnt read yours!
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New Mon 17 Jan 11 20:51 
 Analogue TV plus digital aerial - Old Navy
I'm in for the masthead amp theory too, with the power supply for it near one of the TV's.
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