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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Any RF experts about?
I've just been fitting TV aerials in two new houses - one a relative and
the other their new neighbour who saw what I was up to and wanted theirs done too, for a few beer tokens.. Both jobs took longer than expected. The first was because the darling builders had managed to get both the coax downleads to have whiskers of braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone socket in the living room. (This is quite nice, incidentally - two downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two UHF sockets on the twin faceplate, then a return lead takes your Sky+/ Cable/PVR UHF output back up to a bedroiom socket). The second time, I was ready for the braid to be all over the place and sorted that out first. Then I tried every combination going (on my own, up and loft-ground floor in a 3 storey house loads of times) but nothing I tried got a good signal. With my dying gasp I suspected whoever wired it up was even worse than before and tried the 'return' cable, just on the off chance. That was it. Anyway, on to the point of the post ;-) While looking for possible failure points, I checked out the (new) aerial closely. The only electrical connections were to two alloy 'horns' near the back which I guess the signal is focussed onto. Or rather, the connections were to a small PCB inside the plastic box the horns came out of. The horns were supposedly attached to the core of the coax by having the PCB screwed down onto them - however the large contact pads that would have touched them was still solidly covered in the non-conductive varnish, and the screws went through the non-plated holes without joining the two together electrically. I measured to be sure - yup, no continuity. So I scraped some of the varnish off and got a 1 ohm connection. The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... |
#2
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
PCPaul wrote:
I've just been fitting TV aerials in two new houses - one a relative and the other their new neighbour who saw what I was up to and wanted theirs done too, for a few beer tokens.. Both jobs took longer than expected. The first was because the darling builders had managed to get both the coax downleads to have whiskers of braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone socket in the living room. (This is quite nice, incidentally - two downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two UHF sockets on the twin faceplate, then a return lead takes your Sky+/ Cable/PVR UHF output back up to a bedroiom socket). The second time, I was ready for the braid to be all over the place and sorted that out first. Then I tried every combination going (on my own, up and loft-ground floor in a 3 storey house loads of times) but nothing I tried got a good signal. With my dying gasp I suspected whoever wired it up was even worse than before and tried the 'return' cable, just on the off chance. That was it. Anyway, on to the point of the post ;-) While looking for possible failure points, I checked out the (new) aerial closely. The only electrical connections were to two alloy 'horns' near the back which I guess the signal is focussed onto. Or rather, the connections were to a small PCB inside the plastic box the horns came out of. The horns were supposedly attached to the core of the coax by having the PCB screwed down onto them - however the large contact pads that would have touched them was still solidly covered in the non-conductive varnish, and the screws went through the non-plated holes without joining the two together electrically. I measured to be sure - yup, no continuity. So I scraped some of the varnish off and got a 1 ohm connection. The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... x-posted to uk.tech.digital-tv. Some aerial people there. Andy |
#3
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
"Andy Champ" wrote in message news PCPaul wrote: I've just been fitting TV aerials in two new houses - one a relative and the other their new neighbour who saw what I was up to and wanted theirs done too, for a few beer tokens.. Both jobs took longer than expected. The first was because the darling builders had managed to get both the coax downleads to have whiskers of braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone socket in the living room. (This is quite nice, incidentally - two downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two UHF sockets on the twin faceplate, then a return lead takes your Sky+/ Cable/PVR UHF output back up to a bedroiom socket). The second time, I was ready for the braid to be all over the place and sorted that out first. Then I tried every combination going (on my own, up and loft-ground floor in a 3 storey house loads of times) but nothing I tried got a good signal. With my dying gasp I suspected whoever wired it up was even worse than before and tried the 'return' cable, just on the off chance. That was it. Anyway, on to the point of the post ;-) While looking for possible failure points, I checked out the (new) aerial closely. The only electrical connections were to two alloy 'horns' near the back which I guess the signal is focussed onto. Or rather, the connections were to a small PCB inside the plastic box the horns came out of. The horns were supposedly attached to the core of the coax by having the PCB screwed down onto them - however the large contact pads that would have touched them was still solidly covered in the non-conductive varnish, and the screws went through the non-plated holes without joining the two together electrically. I measured to be sure - yup, no continuity. So I scraped some of the varnish off and got a 1 ohm connection. The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... x-posted to uk.tech.digital-tv. Some aerial people there. Andy It probably would have worked reasonably OK with just the capacitive coupling through the varnish, but this won't be a design feature so you were right to scrape it off and get a solid DC contact. On a similar note, yesterday I re-lamped the display cabinets in the lounge, and I appeared to have a fault with one of the fittings, then I realised the new filament strip-light has a varnish or flux deposit on the solder contacts that needed scraping off. I also have seen the same thing on high wattage flood-light lamps. -- Graham. %Profound_observation% |
#4
Posted to uk.d-i-y
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Any RF experts about?
PCPaul wrote on 30/04/2009 :
I measured to be sure - yup, no continuity. So I scraped some of the varnish off and got a 1 ohm connection. The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... The signal will capacitively couple it through the insulation, but you will get a slightly better signal with the insulation scraped away. What you are looking at is a folded dipole, if it forms a flattened loop. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
#5
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... What make was it?. Wouldn't have been lightning protection anything like that is akin to ****ing on a nuclear explosion let alone a house fire;!... -- Tony Sayer |
#6
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
"Andy Champ" wrote in message news Both jobs took longer than expected. The first was because the darling builders had managed to get both the coax downleads to have whiskers of braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone socket in the living room. Obviously. They always do. The second time, I was ready for the braid to be all over the place and sorted that out first. Then I tried every combination going (on my own, up and loft-ground floor in a 3 storey house loads of times) but nothing I tried got a good signal. With my dying gasp I suspected whoever wired it up was even worse than before and tried the 'return' cable, just on the off chance. That was it. They do this half the time, because it's a 50/50 chance. You just get used to it. We work on the assumption that everything will be wrong. This is usually justified. Some years ago we did a job where the wallplate was incorporated into a fancy 'media plate' which incorporated mains, phone, and TV. These plates were a nightmare to remove and a double nightmare to refit. It was part of the sparks' job to do the aerial/satellite cables. When I went round testing the first one was wired the wrong way round, so I took it off the wall, corrected it, and put it back. This took about 20 minutes! The next one was OK but the next one wasn't. So I put a piece of black tape on it as a marker and moved on. Finally I emailed the sparks to tell them to swap round the cables to about thirty plates. This they agreed to do. But when people started to move in we got a call from someone saying 'no telly' so I went out and sure enough the cables were still the wrong way round. So I passed it back to the sparks, and all further calls to that development were refused until they had been out and tried swapping the cables round. On the same job we had strongly advised the fitting of two sat feeds to each dwelling, but the builder wouldn't pay the extra few quid. Even now we get calls from there about Sky+. While looking for possible failure points, I checked out the (new) aerial closely. The only electrical connections were to two alloy 'horns' near the back which I guess the signal is focussed onto. Or rather, the connections were to a small PCB inside the plastic box the horns came out of. The horns were supposedly attached to the core of the coax by having the PCB screwed down onto them - however the large contact pads that would have touched them was still solidly covered in the non-conductive varnish, and the screws went through the non-plated holes without joining the two together electrically. The mention of 'horns' makes me visualise a DIY or European 'high gain' aerial which will undoubtedly be wideband. I measured to be sure - yup, no continuity. So I scraped some of the varnish off and got a 1 ohm connection. The question (finally) is this: was it designed to pass the energy by RF coupling? No, it's just a **** design. Isn't that a bit lossy on what is a weak signal anyway? Doubt it really. And have I ballsed it up by connecting it electrically? No. I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... No, deffo not lightning protection. x-posted to uk.tech.digital-tv. Some aerial people there. The actual real world beating aerial experts live there actually. Bill |
#7
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
"tony sayer" wrote in message ... The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... What make was it?. Wouldn't have been lightning protection anything like that is akin to ****ing on a nuclear explosion let alone a house fire;!... -- Tony Sayer So half a mil of varnish is going impede a lightning bolt that can travel through thousands of meters of air (quite a good insulator - look at all those 440kV grid cables). |
#8
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
In article , R. Mark Clayton
scribeth thus "tony sayer" wrote in message ... The question (finally) is this: was it designed to pass the energy by RF coupling? Isn't that a bit lossy on what is a weak signal anyway? And have I ballsed it up by connecting it electrically? I guess it could have been some sort of lightning protection, but I can't see it being all that effective, and it's in a loft now anyway... What make was it?. Wouldn't have been lightning protection anything like that is akin to ****ing on a nuclear explosion let alone a house fire;!... -- Tony Sayer So half a mil of varnish is going impede a lightning bolt that can travel through thousands of meters of air (quite a good insulator - look at all those 440kV grid cables). 400 kV so I'm told . Or read.. http://www.edfenergy.com/products-se...N_network_area _132_EHV_NG.pdf -- Tony Sayer |
#9
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer
wrote this:- those 440kV grid cables). 400 kV so I'm told . Between phases, in the UK. 440kV is a voltage used elsewhere though. -- David Hansen, Edinburgh I will *always* explain revoked encryption keys, unless RIP prevents me http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54 |
#10
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
In article ,
David Hansen wrote: On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer wrote this:- those 440kV grid cables). 400 kV so I'm told . Between phases, in the UK. 440kV is a voltage used elsewhere though. It's odd, because upto the time of the supergrid all distribution voltages in the UK were divisible by 11. (440v, 11kV, 33kV, 132kV, 275kV) -- From KT24 - in "Leafy Surrey" Using a RISC OS computer running v5.11 |
#11
Posted to uk.d-i-y,uk.tech.digital-tv
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Any RF experts about?
In article , David Hansen
scribeth thus On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer wrote this:- those 440kV grid cables). 400 kV so I'm told . Between phases, in the UK. 440kV is a voltage used elsewhere though. They use a lot of different voltages elsewhere .. up to 900 kV DC somewhere IIRC... -- Tony Sayer |
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