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TV distribution around the house - again
In message , Graham.
writes "Ivan" wrote in message . com... " wrote in message ... On Jan 25, 1:04 pm, "Dave" wrote: Couple of months ago we moved into this house and, against all the odds, we actually like all the decor as it is and will not be looking to redecorate anywhere for a good long while yet, so running new coax around the place is a no-no for now. Previous owners used (and left in place, so we now use) a 'behind-the-set' aerial distribution amplifier that basically looks like a 13A plug with an aerial input and two outputs. The current setup is a terrestrial aerial feeds into our Sky+ box, RF1 is taken to an adjascent DVD recorder and on to the TV, RF2 is taken to the input of the amp and then a single coax goes around the house to feed an aerial socket in every room. It seems to work alright except that it won't pass the signal for a Sky "magic eye" thingy, meaning that we have to go downstairs to change the Sky channel. Anyone recommend a replacement that will allow us to use a magic eye and second remote upstairs? Thanks It would be interesting -- nay essential -- to know how the one cable going 'all round the house' is connected to all the rooms. The old ring main technique, much used by electricians and would be aerial system installers! Don't forget there is (or was) a legitimate version of this technique using faceplates with built in attenuated tap-offs. Don't forget to wire a 75R resistor across the last one. That certainly was one way of doing it. Each faceplate contained a directional coupler, with the 'tap' port of the coupler feeding the faceplate TV socket, and the 'out' port connected to the ongoing cable. [In some, the tap was diplexed to provide separate TV and FM outputs.] However, this was really only a 'specialised version' of the traditional 'old way' of distributing TV via a string of cascaded tap units. Even though it appears to work OK (for the TV signals), it might be fairly easy (and less hassle) to 'sanitize' the existing system by doing something similar. The existing cable could be retained, but connected to a string of single, separate in-line taps (under the floorboards), located at (or close to) the first six of the aerial sockets. Three taps with values of (say) 16dB followed by three more of 10dB might do the job. [The different values are suggested simply to help to equalise the signal levels at the TV sockets.] The 'tap port' of each would be connected to the existing wallplate TV socket. The 'out port' would be connected to the ongoing cable. To provide a permanent (and adequate) RF termination on the end of the cable, the last TV socket would be connected to the cable via a 10dB attenuator. [Or via another 10dB tap, with its out port terminated.] Obviously, in addition to the existing losses in the cable, there would also be an additional (non-cumulative) loss of 10 or 16dB at the tap, and there would also be the cumulative insertion loss of each tap (say 1dB for a 16dB and 1.5dB for a 10dB). The distribution amplifier would have to have enough gain in hand to make up for these extra losses. The amplifier would have to be of the type designed to pass the magic eye signal (reverse direction). [This could be the problem with the existing one] Note that the remote eye signal would suffer a 10 or 16dB loss back through the tap. [I don't know what is permissible reverse loss is with the Sky equipment.] -- Ian |
TV distribution around the house - again
I suppose if it works, I can't argue....but daisy chaining of sockets
is usually a total desaster and the first thing to do, as everyone says, is to pull it all out and do it properly, a seperate feed from the amp for each socket. However...if the pictures are ok, it is unlikely that a bipass amp made for magic eye use will work. It would be much easier and cheaper to use a "Radio Remote" sender to operate the Sky box from other rooms if they are not too far away. No connections, just a sender and a receiver. (Not a video sender, just a remote sender) http://cpc.farnell.com/remote-control-extenders There are two small blocks of flats nearby, about 12 each block. There is a master aerial for each block and the electricians saw fit to run one cable to each flat from the loft amp and then chain onto three more sockets in each flat. The whole thing has been a desaster from the time they were built and the developer refused to take any responsibility for the first couple of years until the residents had called in various aerial installers and each one had passed the same judgement. I wrote a detailed report and quoted for the job of correction but it was not accepted. Eventually somebody shouted loud enough and something was done..... The next time I was called privately by a resident to sort out their TV, which had virtually no channel 4, I was able to investigate: The firm "correcting" the situation had drilled a hole in each faceplate and managed (just) to pull enough of the outgoing cable from each socket through the hole and then to plug in a cheap "Y" splitter, one output for the set in that room and one for the ongoing cable. The last socket in the chain had 3 splitters before it so you can guess how well it worked ! Further complaints went from the residents to the landlords but with no effect so eventually my customer, who was on the top floor with their own loft, got us to fit a loft aerial, a remotely powered amp and a drop to each room which was easy due to convenient fitted cupboards. Problem solved but I suspect other residents struggle on. A couple of satellite dishes have appeared. |
TV distribution around the house - again
On Jan 25, 7:03*pm, "Graham." wrote:
"Ivan" wrote in media.com... " wrote in message .... On Jan 25, 1:04 pm, "Dave" wrote: Couple of months ago we moved into this house and, against all the odds, we actually like all the decor as it is and will not be looking to redecorate anywhere for a good long while yet, so running new coax around the place is a no-no for now. Previous owners used (and left in place, so we now use) a 'behind-the-set' aerial distribution amplifier that basically looks like a 13A plug with an aerial input and two outputs. The current setup is a terrestrial aerial feeds into our Sky+ box, RF1 is taken to an adjascent DVD recorder and on to the TV, RF2 is taken to the input of the amp and then a single coax goes around the house to feed an aerial socket in every room. It seems to work alright except that it won't pass the signal for a Sky "magic eye" thingy, meaning that we have to go downstairs to change the Sky channel. Anyone recommend a replacement that will allow us to use a magic eye and second remote upstairs? Thanks It would be interesting -- nay essential -- to know how the one cable going 'all round the house' is connected to all the rooms. The old ring main technique, much used by electricians and would be aerial system installers! Don't forget there is (or was) a legitimate version of this technique using faceplates with built in attenuated tap-offs. Yes and it was crap. Believe it or not we still maintain such a system. The skinflints there won't pay for a proper upgrade. It costs them a fortune in call-outs though. Every time a new resident moves in the first thing he does is remove the wallplate and fit a brass one, leaving the outgoing cable disconnected. Don't forget to wire a 75R resistor across the last one. The last one is normally a 12dB tap and the termination is built in. But yes, any value can terminate the line. Bill |
TV distribution around the house - again
On Jan 25, 7:22*pm, "Dave" wrote:
wrote: On Jan 25, 2:29 pm, "Dave" wrote: wrote: Hi Bill and thanks for your interest. A quick furtle about with a screwdriver and continuity tester shows me that a coax leaves the distribution amp, goes out through the wall and up, to re-enter the house under the floorboards in the front bedroom and then goes to a flush mounted socket on the far wall. A second piece of coax leaves from that socket and goes into the back bedroom socket, and from there a third piece of coax dives down into the kitchen etc., etc. All in all, there's seven TV aerial sockets around the house that seem to be wired in a radial fashion, ie, from one to another, to another, to another, ending at the seventh. We've got three TVs (lounge, kitchen and bedroom) and two DVD/HDD recorders (lounge and bedroom). Hope that helps, and thanks again. This isn't radial, it's 'daisy-chain'. Just a semantic point! The arrangement is so far away from any correct way of doing it that I can't really advise you. It's very surprising if it works from the point of view of decent picture quality, and there are lots of possible reasons why a Sky remote eye wouldn't work -- too numerous for me to list. If you called any decent installer out to this he would say that the only thing to do would be to start again and run separate cables from each TV outlet to a common point. At that point an amplifier with 'remote eye passthough' would be fitted. Others will no doubt suggest a various measures which might the remote eyes work, but the thing will always be unreliable and unpredictable, so personally if I were you I wouldn't waste my time -- I'd start from scratch and install a proper system. Thanks for that Bill. Unfortunately (as far as this is concerned anyway) it's going to be at least a couple of years before any redecorating needs to be done, so no chance of taking a hammer and chisel to anything yet. Picture-quality-wise, worst case scenario is/was two TVs on and the two DVD/HDD recorders actually recording - and everything seems to be fine, no problems at all. Maybe it shouldn't work, but it is - except for the sky remote eye *:-) Cheers anyway mate.- Sorry to be a bore, but the fact is, if you put 9V on the daisy chain to power the remote eye it will appear across all the outlets, and there's a good chance a telly or something will short it out. The phenonomal amount of mismatch will make it unlikely that the remote eye return signal will get back to the Sky box. The whole thing will be inherently unreliable. Bill Bill |
TV distribution around the house - again
On Jan 26, 12:47*am, widgitt wrote:
There are two small blocks of flats nearby, about 12 each block. There is a master aerial for each block and the electricians saw fit to run one cable to each flat from the loft amp and then chain onto three more sockets in each flat. The whole thing has been a desaster from the time they were built and the developer refused to take any responsibility for the first couple of years until the residents had called in various aerial installers and each one had passed the same judgement. I recently had cause to write the following email: Hello xxxxx, I’ve done my best with this, and the residents I dealt with are happy, but there are problems that couldn’t be fixed today. 1. In the flats I visited the installers have connected the cable from the head-end to the bedrooms only. The only TV cable running to the living room is an extension from the bedroom. This makes it difficult/ impossible to get everything working in both rooms. Botched attempts had been made to feed signals to both rooms from one cable. I guess the same thing has been done in some or all of the other flats. 2. The cable used is not TV cable; it is CCTV cable. This cable is not suitable for terrestrial TV and is very unsuitable for satellite use. The cable loses a very large proportion of the signal. This makes it very difficult to provide adequate signal levels in the flats, and exacerbates the problems caused by the fact that the only cable from the head end goes to the bedroom instead of the living room. It isn’t even good quality CCTV cable; really weird stuff that won’t strip properly. 3. The (cheap and nasty) aerial is tied to a pipe and I cannot make it secure. The aerial can move in the wind because the pipe twists round. 4. In an attempt to compensate for the cable being the wrong type the head end signal levels are excessively high, causing some distortion. 5. Because the local relay transmitter is close signals arrive at the TV sets without passing though the TV system. Since the signals from the system are weak these ‘direct’ signals cause interference. There isn’t much that can be done about (1) and (2) except respond to any individual complaints and just try in each case to find a solution that works well enough for the resident to accept. It will be a fudge every time, but there’s not much else we can do. Regarding the aerial, if this was closer to home I would automatically go back with a ground stand (etc) and put a new aerial up on the high flat roof. Not a cheap job and at this distance the cost would be even higher, so I’ll do nothing until and unless instructed by you. Incidentally, this system uses the local relay transmitter. At digital switchover this relay will replace the analogue signals with digital ones, using three of the same channels. Therefore no alterations to the system will be necessary as a direct consequence of digital switchover. Attached are a few pictures for your delectation and delight. Bill |
TV distribution around the house - again
On Jan 26, 12:47*am, widgitt wrote:
The firm "correcting" the situation had drilled a hole in each faceplate and managed (just) to pull enough of the outgoing cable from each socket through the hole and then to plug in a cheap "Y" splitter, one output for the set in that room and one for the ongoing cable. The last socket in the chain had 3 splitters before it so you can guess how well it worked ! In 2005 I was called to an 11 storey block that had four flats on each floor (except the ground floor which had three). I was met by the caretaker who was an old man (about my age). He explained that the TV reception problems had been gradually getting worse for many years, and were now particularly acute on the lower floors. He told me with some pride that he had 'kept the aerial working' by responding to individual complaints. In most cases he had found that the replacement of the wallplate brought about a big improvement. However, he warned me, it was important to connect both cables to the new wallplate or people in the flats below lost their reception. For twenty years he had been gradually removing the padded outlets and replacing them with ones from the local DIY shop. These were non-isolated and non-padded. The lower floors had very poor reception indeed. I spoke to the chairman of the residents' association over a cuppa and explained that a proper job would involve running new cables externally. But a quick fix was needed, because a new system wasn't going to happen overnight. OK, well if a botch is justifed I can be a super botcher! I went into every flat on Level 8 and fitted an amp with 30dB gain and high output capability, between the incoming and outgoing cables. The amps were just loose on the floor in corner of the room. I then gave the caretaker a bag of 12dB attenuators and brief instructions as to how to respond to complaints. This works embarrassingly well, and it was hard to get the residents' assn to understand that further repairs were necessary. In the end a new system went in, but without Sky+, which they couldn't 'see the point of'. Bill |
TV distribution around the house - again
On Jan 26, 1:21*pm, Paul Martin wrote:
In article , * * * * wrote: Don't forget to wire a 75R resistor across the last one. The last one is normally a 12dB tap and the termination is built in. But yes, any value can terminate the line. Being pedantic: how about 0R or 10M? -- Paul Martin Sorry, what I wrote was ambiguous. No, I'll come clean. It was downright misleading. By' terminate the line' I meant 'be the last tap on the line'. The impedence matching terminator would normally be 75 ohm, but of course in theory for a very low value tap it should be a slightly higher value. Actually, these padded outlet lines are a total mess in terms of matching. Not so bad if the linking cables are long because (since the cable used was often a lossy type) the reflections 'got lost' to some extent. But a system with CT125 links and only 3m between outlets (a drop down a stack of flats) can be just a nightmare really. Bill |
TV distribution around the house - again
Another interesting set-up in our area is the set of newly converted
barns. About 6 of them. Nice buildings, split level and 4 or 5 bedrooms each and about 8 aerial sockets per house. One of my existing customers bought one and called me when they moved in, to set up the tvs etc. I got very poor results so I assumed, as usual for a new house, that there was no aerial. However the owner told me that the builder had stated that there was an aerial and distribution provided..he knew as he had done that part himself ! I was now suspicious. I checked a few of the other sockets and the signals were different in each room, some channels high and some low but overall very poor. I decided to check the aerial first and, having discovered three diferent lofts, I found it eventually in one of them. A perfectly good Antiference XG lying on the floor. I couldnt see the rest of the set-up as the cable disappeared through a wall. Obviously the first thing was to see if it was able to work in the loft and then set it up correctly. I mounted it high up and aligned it with the analyser and the signal was very good and well balanced across the channels (just analogue at the time). Downstairs it was another matter entirely. The signals still varied widely from room to room and channel to channel although they were overall a bit better. Back to the loft I traced the cable to the next roofspace. It went to a masthead amp then a power supply about 6 inches away and then to a two way set-back amplifier. Two cheap cables came from it and disappeared into the rest of the house. To cut an even longer story short, the builder had wired the whole thing as a ring circuit. Starting at the amp, running round the house to each of about 8 sockets and back to the amp ! The customer phoned the builder there and then, had a rather forceful conversation with him, and handed the phone to me to explain. I would rather have written a report, to be honest, but it was too late for that. I explained exactly what was wrong and received a torrent of abuse for not knowing what I was talking about and was told that he had wired all of the houses he had built in the same way. It was perfectly good and there had never been any problems! The whole story carried on for some time as different people moved into their new houses and found poor results.. After a lot of fuss the builder agreed to get us to correct things as well as we could and he paid up but the systems are still a problem. |
TV distribution around the house - again
On Jan 27, 1:22*am, widgitt wrote:
To cut an even longer story short, the builder had wired the whole thing as a ring circuit. Starting at the amp, running round the house to each of about 8 sockets and back to the amp ! Years ago I was asked to fit an aerial in the loft of a large house that had been converted into a 32 room old people's home. In the loft the builder proudly showed me two coaxes, saying, "I've brought both ends up to the loft so you can connect the aerial to both." I said, "Yer wot?" and he expanded his explanation. The TV sockets in all 32 rooms and two lounges were in one loop. The eventual outcome was that an external surface fixed system was installed, but was only after a prolonged period of poor reception/no reception for the residents. Bill |
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