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550 posts

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# 215578 3-Jul-2017 17:25
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My mum's TV now has trouble producing clear pictures off an old high-gain UHF antenna dating back to when SKY installed it in the mid-1990's. The TV is plugged into a small amplifier which is then plugged into the cable that goes to the antenna. This system has worked well for Freeview's UHF service for several years until fairly recently. Her home is in Kohimarama (Eastern Suburbs of Auckland) and the UHF antenna is pointed toward Pine Hill on the North Shore.

 

About two years back there was a big storm and the UHF antenna fell off the metal pole and came to a rest on the roof, out of alignment with the TX but to my surprise the TV still managed obtain a clear signal with the occasional issues (usually during severe weather events). Somehow the antenna was put back onto the pole and seems to be properly aligned with Pinehil again. The current issue has only cropped up quite some time after the antenna was put back onto the pole.

 

Currently it regularly oscillates between providing a reasonable signal to a degraded signal then back to reasonable again and so on forth. I have some snaps from her Sony TV showing the signal details at its best and at its worst.

 

 

 

Happy to hear any suggestions of what I can look into. If it looks like I need to get someone in to have a proper look and/or fix something I would appreciate recommendations for firms/people I can contact to do that work.

 

Thanks in advance! :)


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  # 1811145 3-Jul-2017 17:45
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Lose the amplifier and go straight into the TV. Symptoms are what I have seen in the past with cellular networks causing amplifier overload. It came and went in cycles, im guessing as the load on the network improved or people moved around with their phones. We put a spectrum on it and there was signals about 30dB higher than the TV ones on the top of the band, so no wonder the amp was having a hard time. Straight into the TV worked mint without getting a filter, but there are filters available quite cheaply if you google lte filter.





Richard rich.ms



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  # 1811151 3-Jul-2017 17:51
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richms:

 

Lose the amplifier and go straight into the TV. Symptoms are what I have seen in the past with cellular networks causing amplifier overload. It came and went in cycles, im guessing as the load on the network improved or people moved around with their phones. We put a spectrum on it and there was signals about 30dB higher than the TV ones on the top of the band, so no wonder the amp was having a hard time. Straight into the TV worked mint without getting a filter, but there are filters available quite cheaply if you google lte filter.

 

 

I think you're on to something because Spark has just added LTE 700 MHz to their site across the road from Mum's house. You can see their antennas from her lounge. So your theory about cellular networks causing amplifier overload sounds like a plausible one given the timing.

 

When I turn off the amplifier I can't get a signal but now I think about it I suspect it doesn't pass through the signal when it's off. Didn't think to try plugging it direct (i.e. without the filter) so will try that next time and see what the outcome is.

 

- James


 
 
 
 


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  # 1811186 3-Jul-2017 18:24
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Yeah they dont pass thru much when off, just the parasitic coupling across the devices in it, so a massive loss when off but in circuit.

 

In the UK the telcos were forced to sort out peoples reception problems because thats the madness of the UK for you. In anycase if you can see them and they are on 700MHz then that will be the problem right there.





Richard rich.ms

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  # 1811198 3-Jul-2017 18:52
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If the antenna and cable is that old I'd suggest it's time for a new antenna and cable. The corrosion must be horrendous.


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  # 1812231 3-Jul-2017 20:22
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Depending on where your mum is in Kohi is where I would point the Aerial, Pine hill is a good option as is Remurea and Skytower.

 

My standard reply in these cases are to get an installer who has the proper equipment, in this case a proper field strength meter will be worth it's weight in gold. Most installers will not have a spectrum analyzer so dont expect that. ( some field strength meters do satellite as well and can be a spec an )

 

New cable which is quad shielded, decent crimp connectors and a decent antenna with a good front to back ratio will knock a lot of the side signals and anything from the rear.

 

I dont know if there are any 700MHz - 950MHz filters but one of those would help too.

 

 

 

John

 

 





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  # 1812232 3-Jul-2017 20:24
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Any recommendations for good installers?


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  # 1812234 3-Jul-2017 20:25
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Buy this. Plug it in before the amplifier (hopefully plugs are right) and see what happens.

 

https://www.jaycar.co.nz/4g-lte-filter-for-digital-tv-reception/p/LT3062





Richard rich.ms

 
 
 
 


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  # 1821779 13-Jul-2017 12:35
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Just following this thread. I'm having some issues with UHF reception myself, especially into a DVB-T card in a PC. Thanks for any suggestions.




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  # 1822334 14-Jul-2017 11:00
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Bought the filter last weekene and went to mum's house to test it out. This time I took an outside photo of the set up. You can see the exisiting VHF and UHF antennas. The UHF one is slightly lopsided but seems to be in the right direction.

 

Click to see full size

 

I put the filter between the ampifier and the TV. Basically something like this: Cable from hole in floor (screw type connector) --> ampifier (with screw type connector on both ends) --> (screw) cable (standard TV plug) --> filter (standard TV connectors both ends) --> TV. Doing this seemed to give a noticable improvment (and mum seemed to think so too). But the signal quality still drops every so often (but not as often as without the filter).

 

Click to see full size

 

I tried to rearrange the cables to take the ampifier out of the equation but the cable from the floor has a different screw-type end I'm not familiar with. I tried connecting the cable from the hole in the foor with the other cable and while it seemed to connect physically, when I plugged it into the TV there was no signal so perhaps I was doing something wrong. Resetting it back to the original confiuration worked fine but obviously with the issue present.

 

Click to see full size

 

My thinking at this point it's probably for the best to scrap the exisiting installation and just get an installer to install a new UHF antenna and new cabling direct to the only point where there is a TV. The exisiting arrange actually inclues splitters to three points, two of which no longer has a TV connected which I am sure does not help at all. Hopefully a good set up will avoid the need for an ampifier etc.

 

Is there any recommendations for aerial installers in the East Auckland area? I had a look at the yellow pages and Auckland Aerials looks good. Any feedback on them? Or are there any Geekzoners around who do this work for a living?


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  # 1822352 14-Jul-2017 11:13
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Yep, replacing antenna and cable seems like the best option.

 

Removing the VHF antenna at the same time will help as well, both in reducing the windage on the mast, but it will help reception as well if they are running down the same cable (and, the aluminium elements form the VHF antenna make great garden stakes!)


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  # 1822372 14-Jul-2017 11:41
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trig42: (and, the aluminium elements form the VHF antenna make great garden stakes!)


Don't stick anything in the garden you wouldn't like to sit/fall on.

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  # 1822375 14-Jul-2017 11:43
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KiwiSurfer:

 

 

 

I tried to rearrange the cables to take the ampifier out of the equation but the cable from the floor has a different screw-type end I'm not familiar with. I tried connecting the cable from the hole in the foor with the other cable and while it seemed to connect physically, when I plugged it into the TV there was no signal so perhaps I was doing something wrong. Resetting it back to the original confiuration worked fine but obviously with the issue present.

 

Click to see full size

 

My thinking at this point it's probably for the best to scrap the exisiting installation and just get an installer to install a new UHF antenna and new cabling direct to the only point where there is a TV. The exisiting arrange actually inclues splitters to three points, two of which no longer has a TV connected which I am sure does not help at all. Hopefully a good set up will avoid the need for an ampifier etc.

 

Is there any recommendations for aerial installers in the East Auckland area? I had a look at the yellow pages and Auckland Aerials looks good. Any feedback on them? Or are there any Geekzoners around who do this work for a living?

 

 

What you are referring to as an amplifier (and show in the image) is actually the power supply for a masthead amp up on the roof. It will be amplifying both VHF and UHF signals which is probably the main source of your problems. You need to remove the VHF antenna completely. The masthead amp may probably still be needed depending on which transmitter the antenna is pointing at and what signal strength is available at the antenna. Connecting the cable from the floor direct to the TV would have resulted in no signal because you removed the power from the masthead amplifier. IMO You definitely need a Pro installer with the appropriate gear to get it all sorted.




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  # 1822488 14-Jul-2017 14:12
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B1GGLZ:

 

 

 

What you are referring to as an amplifier (and show in the image) is actually the power supply for a masthead amp up on the roof. It will be amplifying both VHF and UHF signals which is probably the main source of your problems. You need to remove the VHF antenna completely. The masthead amp may probably still be needed depending on which transmitter the antenna is pointing at and what signal strength is available at the antenna. Connecting the cable from the floor direct to the TV would have resulted in no signal because you removed the power from the masthead amplifier. IMO You definitely need a Pro installer with the appropriate gear to get it all sorted.

 

 

Now that makes sense. Thank you for your insight, never thought it would be a power supply to an ampifier on the roof.


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