Decimalz Posted May 23, 2008 Posted May 23, 2008 Our housing estate (Belmont, Perth, WA) TV reception is provided by an MATV system. We get intermittent interference which is mainly pixelation and a gap in sound or sound appearing to be out of sync with the picture when we are watching DTV. On an analogue system it appears as strong horizontal white lines which some times includes the picture also losing sync. I have been to several houses over the site and all houses are affected i.e. both digital and analogue. I am under the impression it is electrical or RF interference, but where it is getting into the system is unknown. Should each house be isolated from feedback? i.e. should each of the taps (which are housed in the underground pit system) be isolated to stop any signal entering the system from the house? If not do you think this interference could be coming from any house which may have a faulty stb/vcr/tv? Also, the cabinet which houses the main MATV head end has no ventilation and it seems to be getting very hot inside. You can feel the heat emitting from the headend through the closed door! Any answers or feedback would be greatly appreciated.
digitalj Posted May 23, 2008 Posted May 23, 2008 do you get the picture breaking up when you turn lights on/off?
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 do you get the picture breaking up when you turn lights on/off? No, it doesn't seem to be caused directly by any electrical switch or general power outlet in the house. Though do you think the 'sparks' say of another property in the estate could be causing this? i.e. when they turn their lights on or off or use a power outlet to boil a kettle etc?
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 Would in-line isolators installed on the hardline cable entering the headend rectify this problem?
digitalj Posted May 23, 2008 Posted May 23, 2008 Is Every Cable RG6 Quad shield and every joint F-connectors?
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 Hard-line cable running from the MATV headend to taps in the pit system, which then have RG-11 feeding from the taps to the houses splitters, then RG-6 feeding from the splitter to the TV points.
I am not a duck Posted May 23, 2008 Posted May 23, 2008 (edited) While you may get advice here regarding your problem, ultimately engaging the services of a competent technician with experience in MATV systems is the correct procedure. Also, your enquiry may be more readily addressed by posting in the correct geographical forum. This might enable comments specific to your area to be more forthcoming. Edited May 23, 2008 by M'bozo
I am not a duck Posted May 23, 2008 Posted May 23, 2008 (edited) Edit: Forum dead slow causing double post. Edited May 23, 2008 by M'bozo
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 The technician who did the head-end and the design of the system is very competent, one of the best in WA in fact. It's why this problem is so baffling.
digitalj Posted May 23, 2008 Posted May 23, 2008 does everyone use the cheap $2 type of Flyleads for connecting the TV outlet to their TV/STB? These don't have very good shielding, and should be replaced by Flyleads made from RG6 Quad Shield.
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 does everyone use the cheap $2 type of Flyleads for connecting the TV outlet to their TV/STB? These don't have very good shielding, and should be replaced by Flyleads made from RG6 Quad Shield. Yes, most of the residents do use the cheap leads. Would this be allowing/causing feedback from the T.V./STB to be re-entering the system?
I am not a duck Posted May 23, 2008 Posted May 23, 2008 So the system is therefore installed to AS1367:2007. Has the half split method of troubleshooting been used to determine at which point the fault commences? Is the problem visible off-air at the primary reception point?
Decimalz Posted May 23, 2008 Author Posted May 23, 2008 Has the half split method of troubleshooting been used to determine at which point the fault commences?Is the problem visible off-air at the primary reception point? As far as I know the half-split method hasn't been used. I'm not even sure what that is! Could you please explain? No, I don't think the problem is visible off air from the primary reception point.
digitalj Posted May 23, 2008 Posted May 23, 2008 As far as I know the half-split method hasn't been used. I'm not even sure what that is! Could you please explain?No, I don't think the problem is visible off air from the primary reception point. I think M'bozo is saying a test at the antenna, a test at the tap and a test at the outlets, i.e. to see if the fault is happening before or after the tap.
I am not a duck Posted May 23, 2008 Posted May 23, 2008 I think M'bozo is saying a test at the antenna, a test at the tap and a test at the outlets, i.e. to see if the fault is happening before or after the tap. Good call dj. Half split method is essentially a fault finding process using binary progression. --Check the signal at a point in the middle of the system. --Is it good or bad? If it's bad, choose a point midway between there & the front of the system; if it's good, pick a point midway between there & the system output. --Again, is the signal good or bad? --Continue thus, always splitting the remaining section and moving toward the bad area until you find the faulty part.
alanh Posted May 23, 2008 Posted May 23, 2008 All, If the analog signals have the top half of the screen lighter and the bottom half darker which slowly moves vertically it is 50 Hz mains induction. Then it is either an earth loop or induction from power wiring. If the analog signals have a pair of lighter horizontal bars slowly moving vertically it is a power supply rectifier diode(s) faulty and or the power supply filter capacitors. These power supplies are used in the distribution amplfiers and in masthead amplifer if used. AlanH
mtv Posted May 23, 2008 Posted May 23, 2008 The technician who did the head-end and the design of the system is very competent, one of the best in WA in fact. It's why this problem is so baffling. Also, the cabinet which houses the main MATV head end has no ventilation and it seems to be getting very hot inside. You can feel the heat emitting from the headend through the closed door! Very competent technician? Installing a headend in a cabinet without ventilation causing overheating, suggests otherwise! From your description, the interference seems to be impulse noise interference, which may be being picked up by the antenna, amp/s (especially if they are failing to to overheating.. this could even be the primary cause of the interference) poor cabling eg:badly-shielded flyleads, or even through mains cabling. I would recommend you have your 'very competent' tech return, locate the problem and rectify it.
I am not a duck Posted May 23, 2008 Posted May 23, 2008 All,If the analog signals have the top half of the screen lighter and the bottom half darker which slowly moves vertically it is 50 Hz mains induction. Then it is either an earth loop or induction from power wiring. If the analog signals have a pair of lighter horizontal bars slowly moving vertically it is a power supply rectifier diode(s) faulty and or the power supply filter capacitors. These power supplies are used in the distribution amplfiers and in masthead amplifer if used. AlanH There you go Decimalz. AlanH is in Perth. He may be able to assist if you get stuck
Pross77 Posted November 20, 2008 Posted November 20, 2008 Alanh, I hope you get this as I am part of this complex and am actually the chairman of the strata. I have a feeling the person who posted this orignal post was the installer who was "one of the best". yes they used hard line, rg6 and wisi gear yet as you stated they put all the power supplys, amps etc in a sealed steel box next to the full complex power distribution point. Now I am new to this stuff but spent 7 year in the military and spend a lot of time around very high end comms gear. I understand most but may need some explaination with the DTV systems. Issue is the problems went away in late May and are now back! my pioneer STB remains with high signal just the SNR dorp fron high 20's db to near nothing. I pushed the info last time to our contract sparkies who I think had no idea (the installers) Some field info, 1. down stream amps powers supply which is next to the wisi headends hums very loudly and is bloody hot (curtious of no vents). 2. seams to be worse at night from 7 to 10pm. 3. analogue is the horiz white lines moving upwards. 4. the "experts" grounded the system as the original instal did not do this and they stated fixed the problems. 5. I have disconected each one of the three main lines from the headend to isolate parts of the complex but still had interfence so I feel that it is from the headend. 6. the spakies install voltage regulators for the headend power supplies so headend gets solid 240v even though australian power is now 230v. Can you help as it is really anoying to have a 50" plasma that can't be used for tv!!!
Pross77 Posted November 20, 2008 Posted November 20, 2008 Alanh, I hope you get this as I am part of this complex and am actually the chairman of the strata. I have a feeling the person who posted this orignal post was the installer who was "one of the best". yes they used hard line, rg6 and wisi gear yet as you stated they put all the power supplys, amps etc in a sealed steel box next to the full complex power distribution point. Now I am new to this stuff but spent 7 year in the military and spend a lot of time around very high end comms gear. I understand most but may need some explaination with the DTV systems. Issue is the problems went away in late May and are now back! my pioneer STB remains with high signal just the SNR dorp fron high 20's db to near nothing. I pushed the info last time to our contract sparkies who I think had no idea (the installers) Some field info, 1. down stream amps powers supply which is next to the wisi headends hums very loudly and is bloody hot (curtious of no vents). 2. seams to be worse at night from 7 to 10pm. 3. analogue is the horiz white lines moving upwards. 4. the "experts" grounded the system as the original instal did not do this and they stated fixed the problems. 5. I have disconected each one of the three main lines from the headend to isolate parts of the complex but still had interfence so I feel that it is from the headend. 6. the spakies install voltage regulators for the headend power supplies so headend gets solid 240v even though australian power is now 230v. Can you help as it is really anoying to have a 50" plasma that can't be used for tv!!!
I am not a duck Posted November 20, 2008 Posted November 20, 2008 (edited) Comments deleted when I realised the previous post is directed to someone else. Edited November 20, 2008 by M'bozo
beeblebrox Posted November 26, 2008 Posted November 26, 2008 Alanh,I hope you get this as I am part of this complex and am actually the chairman of the strata. I have a feeling the person who posted this orignal post was the installer who was "one of the best". yes they used hard line, rg6 and wisi gear yet as you stated they put all the power supplys, amps etc in a sealed steel box next to the full complex power distribution point. Now I am new to this stuff but spent 7 year in the military and spend a lot of time around very high end comms gear. I understand most but may need some explaination with the DTV systems. Issue is the problems went away in late May and are now back! my pioneer STB remains with high signal just the SNR dorp fron high 20's db to near nothing. I pushed the info last time to our contract sparkies who I think had no idea (the installers) Some field info, 1. down stream amps powers supply which is next to the wisi headends hums very loudly and is bloody hot (curtious of no vents). 2. seams to be worse at night from 7 to 10pm. 3. analogue is the horiz white lines moving upwards. 4. the "experts" grounded the system as the original instal did not do this and they stated fixed the problems. 5. I have disconected each one of the three main lines from the headend to isolate parts of the complex but still had interfence so I feel that it is from the headend. 6. the spakies install voltage regulators for the headend power supplies so headend gets solid 240v even though australian power is now 230v. Can you help as it is really anoying to have a 50" plasma that can't be used for tv!!! Pross77, some info on what the headend is, it's config and channels used wouldn't hurt... As previously stated measuring checking the signal at the entrance point ie before the head end when these problems are occuring would be the first thing I'd be checking to see if it's external interference or something within the system the analogue white linse could be an amplifier problem , either overload or power supply or some ac noise.. BER's across each channel need to be monitored before and after the headend to see where the problem is. Are the analogue channels transmodulated digital channels or are they just be amplified from the off air signal? Any info you have would be useful in assisting you.
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