My Humax Forum » Freeview HD » HDR 1800T, 2000T

'Short Circuit' error with 5v Antenna Power.

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    Roy22

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    OK, so I'm setting up my HDR2000T in a new house/new city, where signal strength is rather lower than my previous location. The aerial looks fairly new, and the previous owner seems to have been pretty keen on electrical improvements, so I thought I'd turn on the 5v Antenna Power, just in case a booster was fitted somewhere up in the loft etc.

    This gives an error about a 'Short Circuit' each time I try turning it on. After playing with different coaxial cables to no improvement, I tried turning the 5v on with no aerial lead plugged in at all to the Humax. The error remains.

    So, what does this mean? A hardware, or software fault somewhere? It works fine otherwise.

    | Thu 6 Jul 2017 18:28:48 #1 |
  2. grahamlthompson

    grahamlthompson

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    It simply means there is no amplifier that requires power connected to the aerial. Many aerials are a short circuit to DC. The active element may be a simple loop made of aluminium which is of course a total short circuit to DC.

    At a guess you need to turn off the power to the box after turning off the DC power option, to reset the DC overcurrent protection trip resulting from you turning it on.

    Signal strength is not important, if the quality is 100% you have nothing to worry about. My weakest mux are about 40% but with quality at 100% reception is rock solid.

    | Thu 6 Jul 2017 19:25:33 #2 |
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    Roy22

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    Many thanks Graham, I hadn't realised that ordinary aerials were a virtual short. And you've confirmed what I suspected, that's it's quality not quantity that matters for digital reception.

    One other question then. I think I'm still on the Sutton Coldfield transmitter (any way to know?) but much further away. Some pretty trivial minor channels are now gone, which I won't miss. But BBC4 HD is now gone, just standard definition BBC4 on Ch9 remains. Would a powerful enough signal booster restore the HD channel?

    | Thu 6 Jul 2017 21:39:14 #3 |
  4. Biggles

    Biggles

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    Roy22 - 43 minutes ago  » 
    Many thanks Graham, I hadn't realised that ordinary aerials were a virtual short.
    *****

    Not a virtual short but an actual short circuit, however some aerials are open circuit (like mine), it depends on the design. I believe some amplified indoor aerials use this built in 5v supply.

    | Thu 6 Jul 2017 22:27:02 #4 |
  5. grahamlthompson

    grahamlthompson

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    Roy22 - 11 hours ago  » 
    Many thanks Graham, I hadn't realised that ordinary aerials were a virtual short. And you've confirmed what I suspected, that's it's quality not quantity that matters for digital reception.
    One other question then. I think I'm still on the Sutton Coldfield transmitter (any way to know?) but much further away. Some pretty trivial minor channels are now gone, which I won't miss. But BBC4 HD is now gone, just standard definition BBC4 on Ch9 remains. Would a powerful enough signal booster restore the HD channel?

    Bear in mind I don't have a 2000T so the following information is based on the very similar earlier HDR-FOX-T2 which has a very similar User Interface.

    Check what transmitter you are on.

    https://ukfree.tv/transmitters/tv/Sutton_Coldfield/PGSTART2480/

    Make a note of the UHF channel used by each Mux - eg PSB1 is C43.
    Note the power of the COM 7 mux which carries BBC 4 HD, PSB 1 200kW Com 7 89.2kW. That's why you have lost BBC 4 - HD and the other COM 7 channels. More later.

    On your box

    Press list Move to one channel from each Mux and press info it will tell you the UHF Mux you are using it should match the list you created above. eg BBC1-HD C43.

    Check your predicted reception - Use the detailed view by entering your postcode here.

    http://www.digitaluk.co.uk/operations/about_the_coverage_checker

    Improve signal levels hopefully to pick up COM 7

    Fit a low noise masthead amplifier with variable gain as close to the aerial as possible - hint if your downlead goes into the loft you can fit the amplifier in the loft. 12V power is supplied by a remote PSU.

    Adjust the gain to give best quality, be careful not to over amplify the high power mux as this will create problems from tuner overload.

    Basically adjust the gain to a level that brings in COM 7, you might have to fine tune depending on how you get on in bad weather.

    This one has 4 outputs so you can use it to feed 4 or more extra TV's. It should have enough gain to use passive splitters. I have one that feeds 10 tuners mounted in my loft.

    https://www.amazon.co.uk/Vision-V20-4260L-Masthead-Amplifier-Booster/dp/B00MEPIUUG

    Alternatively start by changing the aerial to a better design. You may not need the amplifier.

    I can recommend the log 36 which I use.

    https://www.amazon.co.uk/AERIAL-STUB-TUNING-LTE-AT800-V10-36L-VISION/dp/B0118KKW0S

    Hint use the manual tune option to check and set up new aerial and/or amplifier. Select the mux channel and DVB-T for SD mux and DVB-T2 for HD mux including com 7.

    | Fri 7 Jul 2017 9:17:24 #5 |
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    Roy22

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    Dear Graham,

    Many thanks for the detailed reply. It does appear I'm on the Sutton Coldfield transmitter, with the weaker MUXs vanished off the radar.

    Re the Masthead amplifier, I've been up in the loft and was pleased (in a problem solving sense) to find a crudely taped-up joint where the incoming aerial wire is joined to two others headed off to wall sockets, possibly more than two wall sockets (house full of boxes still!), could they be chained one after another?

    A bad tape-up job is not how to join coax and so gives me hope for improvement. My plan is to put a Masthead amplifier as you describe replacing this junction point.

    But one spurious question. FM radio reception isn't wonderful either (and DAB seems reduced in channel range). Would the amplified TV aerial offer any improvement for FM, or will such frequencies have been filtered out?

    | Sun 9 Jul 2017 17:46:33 #6 |
  7. grahamlthompson

    grahamlthompson

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    Roy22 - 29 minutes ago  » 
    Dear Graham,
    Many thanks for the detailed reply. It does appear I'm on the Sutton Coldfield transmitter, with the weaker MUXs vanished off the radar.
    Re the Masthead amplifier, I've been up in the loft and was pleased (in a problem solving sense) to find a crudely taped-up joint where the incoming aerial wire is joined to two others headed off to wall sockets, possibly more than two wall sockets (house full of boxes still!), could they be chained one after another?
    A bad tape-up job is not how to join coax and so gives me hope for improvement. My plan is to put a Masthead amplifier as you describe replacing this junction point.
    But one spurious question. FM radio reception isn't wonderful either (and DAB seems reduced in channel range). Would the amplified TV aerial offer any improvement for FM, or will such frequencies have been filtered out?

    If you replace the bodged taped up effort with a proper splitter before you do anything you may well find that your problem is solved. Without the impedance matching that you get in a proper splitter you get allsorts of signal reflections. Add a 3 way splitter first with DC pass to allow a masthead amp afterwards if you need one.

    http://www.labgear.co.uk/product-categories/splitters-filters/splitter-splitters-filters/uhf-3-way-splitter-power-pass-ports/

    http://www.aerialsandtv.com/ampsandsplitters.html#AmplifierOrSplitter

    A UHF aerial will get virtually no signal in the VHF band (they are designed to receive only UHF band signals) the splitter itself or any amplifier will not be the issue, the solution is pretty easy. A combined DAB/FM VHF aerial connected via a UHF/VHF diplexer before the splitter will send the signal down the coax.

    See aerial response curves

    http://www.aerialsandtv.com/tvaerialtests.html

    eg

    https://www.ebay.co.uk/i/172519570438?chn=ps&dispItem=1&adgroupid=45192391362&rlsatarget=pla-327465392370&abcId=1129006&adtype=pla&merchantid=107686325&poi=&googleloc=9041125&device=c&campaignid=861899735&crdt=0

    You need the same device at the other end to seperate the UHF TV signals from the two VHF bands used by DAB and VHF.

    http://www.aerialsandtv.com/ampsandsplitters.html#DiplexedTelevisionPlusFM

    I can recommend Justins ATV aerial site for all sorts of info re terrestrial TV and radio reception.

    http://www.aerialsandtv.com/index.html

    | Sun 9 Jul 2017 18:37:13 #7 |
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    Roy22

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    OK, so I took your advice and bought the Masthead amplifier you recommended. I didn't fit it on the mast, but pretty close by in the loft just where the coax enters. I'm glad to say it brought back my missing (lesser) Freeview HD channels! Quality is 100% whereas strength seems 50-70%.

    One thing though. On retuning, the Humax asked Country\Area\Region or something to that effect, and I chose GBR\England\West Midlands, the latter due to pointing at the Sutton Coldfield transmitter. Afterwards, I wondered if that was a mistake (I'm more in the East Midlands really) but I wondered where this region question came from? Because new channels were detected? My Freeview always TV asks these region questions after a retune, but not my Humax to the best of my memory.

    Retuning again a couple of times, the regional question did not reappear. Why?

    | Mon 17 Jul 2017 19:41:24 #8 |
  9. grahamlthompson

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    Roy22 - 15 minutes ago  » 
    OK, so I took your advice and bought the Masthead amplifier you recommended. I didn't fit it on the mast, but pretty close by in the loft just where the coax enters. I'm glad to say it brought back my missing (lesser) Freeview HD channels! Quality is 100% whereas strength seems 50-70%.
    One thing though. On retuning, the Humax asked Country\Area\Region or something to that effect, and I chose GBR\England\West Midlands, the latter due to pointing at the Sutton Coldfield transmitter. Afterwards, I wondered if that was a mistake (I'm more in the East Midlands really) but I wondered where this region question came from? Because new channels were detected? My Freeview always TV asks these region questions after a retune, but not my Humax to the best of my memory.
    Retuning again a couple of times, the regional question did not reappear. Why?

    Perhaps because you are now picking up channels from more than one transmitter that were found on a auto tune. Have you channels in the 800's. If so post for manual tuning instructions. If you have not selecting West Midlands (the correct answer) should have removed them. It's not where you live it's the transmitter location. Sutton Coldfield is firmly in the West Midlands so provided no 800+ channels everything is fine.

    | Mon 17 Jul 2017 20:01:22 #9 |
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    Roy22

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    No, 698 is the highest channel I have. Glad I picked the right answer!

    | Mon 17 Jul 2017 20:15:38 #10 |

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