My Humax Forum » Freeview HD » YouView DTR-T models

Signal Strength Meter on YouView Box

(7 posts)
  1. tellboy

    tellboy

    member
    Joined: Jan '13
    Posts: 19

    offline

    I live within line of sight of Winter Hill Transmitter.
    You can get a TV picture with a bit of wet string, nevertheless even though the aerial fitter told me I didn't need one , I still recently had a high gain aerial fitted.
    My Panasonic TV reports 100% Strength 100% Quality on the signal strength display.
    All of the Humax FreeView equipment I have ever used reported about 65% strength and 100% quality. I always wondered why but it was never a problem.
    The YouView DTR-T1000/T1010 reports the same but I am still getting areas of the screen boxed out for a second or two and occasional loss of signal messages.
    Flicking over to the TV during these episodes no screen problems and 100% strength.
    The aerial goes to the Youview box and then to the TV.
    Connection is to a latest Panasonic TV on HDMI1.
    All connections are good. Do other get similar figures ?
    Humax Support do not respond at all to emails even as concise as this explanation but apparently wait for phone calls I gather ?

    Thu 28 Mar 2013 15:43:55 #1 |
  2. User has not uploaded an avatar

    grahamlthompson

    special member
    Joined: Feb '11
    Posts: 4,232

    online

    Too much signal is as bad as too little especially if the kit has sensitive tuners. You would have done better fitting a log periodic antenna. Try fitting a uhf attenuator.

    http://www.ebay.co.uk/itm/TV-Aerial-Attenuator-Variable-0-20Db-Freeview-Digital-1ST-CLASS-SAME-DAY-/221181804245?pt=UK_ConElec_TVAerials_RL&hash=item337f767ed5

    A uhf-uhf splitter before the Humax will drop the signal level about 3.5dB and will allow the TV to have a direct feed so you can use power saving on the Humax.

    Thu 28 Mar 2013 16:13:00 #2 |
  3. tellboy

    tellboy

    member
    Joined: Jan '13
    Posts: 19

    offline

    Thanks I will try that but why would the Humax report only 65% signal strength on almost all the stations and even did that on a very old normal aerial on other Humax boxes ?

    Sun 31 Mar 2013 15:27:24 #3 |
  4. User has not uploaded an avatar

    grahamlthompson

    special member
    Joined: Feb '11
    Posts: 4,232

    online

    tellboy - 6 minutes ago  » 
    Thanks I will try that but why would the Humax report only 65% signal strength on almost all the stations and even did that on a very old normal aerial on other Humax boxes ?

    If you have a variable output amplifier capable of driving the tuner front end into clipping then what happens is that as you boost the signal gradually the indicated signal strength and quality will go up until you get to the optimum quality. Increasing the gain more will continue to indicate more signal for a while but the quality will decline as the digital in built error correction has to work harder to cope. Eventually the tuner front end amp has such a distorted waveform that the measured signal actually falls. Often the signal level will fluctuate wildly as well.

    I could be totally wrong and this is not the cause but it's certainly worth trying, especially as you say you can actually see the transmitter.

    The power output used by digital transmitter was greatly increased at dso, in some cases to get reception pre dso high gain aerials and amplifiers were used. Come dso you don't need all that gain.

    Sun 31 Mar 2013 15:42:57 #4 |
  5. tellboy

    tellboy

    member
    Joined: Jan '13
    Posts: 19

    offline

    Thank you for the additional info.
    i also found this on Google

    UHF Attenuators

    When a Freeview receiver detects a signal which is too strong, its automatic gain control (AGC) adjusts the tuner gain down to compensate. If the signal is _way_ too strong, the AGC tries to protect the receiver by overcompensating and turning the gain down much further. The result is often that the signal level display is quite low when the signal is way too high.

    Adding an attenuator reduces the incoming signal, causing the AGC to "relax" and the signal reading will go up!

    So you can't rely on an on-screen signal indication to measure signal level. It's purely a guide (and not a very good one). The only way to measure an aerial signal is with a properly calibrated aerial signal meter. Unfortunately, the cheapest one we stock is well over a hundred pounds.

    I did some tests on my own aerial system (which gives perfect results on all channels). I have a good, strong signal but not overly strong. I found that I could insert 30dB of attenuation in the aerial input before the on-screen 100% indication started to fall. In the case of a way-too-strong signal I would expect to need more than 30dB attenuation to get the signal down to a reasonable level that the receiver could handle. Perhaps even as much as 40dB. If you have a really strong signal, you might need a couple of fixed attenuators plus a 20dB variable attenuator to get the level right.

    There is very little to go wrong with our attenuators, apart from the adjustor breaking off. There's no electronics inside.

    Mon 1 Apr 2013 15:23:20 #5 |
  6. tellboy

    tellboy

    member
    Joined: Jan '13
    Posts: 19

    offline

    I tried a 20db attenuator.
    This reduced the signal strength from a displayed value on channel 1 from 65% to about 30% so I gather that the signal strength is not too strong after all.
    Having removed it and back to 65% I am still left wondering what signal strength other users get as typical values.
    Oddly the picture breaking up hasn't happened since starting this thread.

    Fri 5 Apr 2013 15:24:55 #6 |
  7. User has not uploaded an avatar

    grahamlthompson

    special member
    Joined: Feb '11
    Posts: 4,232

    online

    Sutton Coldfield Signal/Quality

    HD FOX T2

    PSB1 71%/100%
    PSB2 68% 100%
    PSB3 (HD Mux) 75%/100%
    COM4 72%/100%
    COM5 71%/100%
    COM6 76%/100%

    HDR FOX T2
    PSB1 80%/100%
    PSB2 72%/100%
    PSB3 84%/100%
    COM4 83%/100%
    COM5 78%/100%
    COM6 83%/100%

    20dB is a lot of attenuation. For example signal strength at DSO went up 10dB. So your signal after DSO would be worse than it was pre DSO.

    Fri 5 Apr 2013 16:05:05 #7 |

RSS feed for this topic

Reply

You must log in to post.