All posts by Tony
Below are all of Tony's postings, with the most recent are at the bottom of the page.
T
Crystal Palace (Greater London, England) Full Freeview transmitTuesday 8 May 2012 7:26PM
Chelmsford
jb38: Sorry. I should have mentioned that I live in Chelmsford, CM1 6SS. Thank you for your comments.
I have a Horizon HDTM meter and it is showing a signal increase of about 3db (from ~27db to ~30db. I had been expecting a greater increase than that.
I have a 0-20db attenuator built into my system. Do you have an optimal db value in mind?
Thanks in advance. I'll get back to you to report my findings.
Tony
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jb38: I tried attenuating my input signal and the HD channels immediately froze and came back when I reduced the attenuation to zero.
Am I right in thinking that the signal is not overloading? Maybe I need a better aerial for HD?
I have had my current setup for over three years.
Tony
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jb38: The plot thickens.
I would have explained earlier (I thought this issue was a simple one, wrongly), but I have a fairly complex setup. My aerial goes into a 0-20 attenuator and then into a Labgear 16 way destribution unit. Four of the outputs from the Labgear go to my WMC PC. Four others go to TVs throughout the house, three of which are HD ready, but don't have Freeview HD. Therefore, I get the HD from WMC extenders attached to my WMC PC (wired).
My Horizon meter shows channels 22, 23, 25, 26 & 28 having a signal strength of 30db. Using WMC I am able to see that all of these channels are giving signal qualities of 100%. As you say, the Horizon meter is no good for HD, so I can only diagnose that WMC reports the HD channel signal strengths are 60%.
WMC scans for channels by region (i.e. country) rather than by transmitter. So, when I setup the TV signal, WMC actually detects more than one source for certain channels. All but the Crystal Palace sources have inferior signal qualities. Where I live in Chelmsford, I get an unrestricted signal from Crystal Palace as I am quite high up with very few houses between me and the fall away of the hill I am at the top of. The aerial is setup to point slightly upwards of horizontal.
I have spoken to an aerial installer on the phone today and was told that the only way to be certain what might be wrong (if at all) is to do a survey. Sadly, they don't cover my area. So, I'll need to find a local installer (one I can trust as I've been stung before and am a bit wary now).
I hope this explains better my setup and how I am able to quantify the signal.
Thanks for your patience
Tony
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jb38: Thank you for your detailed analysis of my situation.
I will try what you suggest and take the attenuator out of the system and measure the reading on the Horizon meter straight from the aerial. I have to say that, as you also suggest, I was expecting a much higher db reading after switchover since the wattage should have gone up to 200,000 watts. It occurs to me that the Horizon meter might be limited to what it can display - so I'll contact Horizon to ask that question.
To switch my aerial around to Sudbury I would need to get a tv engineer out and that is out until I establish the true state of affairs.
FYI, I am using BlackGold BGT 3620 cards in my WMC PC.
I'll get back to you when I have tested the points above. Sigh.....
Tony
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jb38: Okay. I think I've got the story straight.
Firstly, I've been abit of a klutz and was not reporting the correct signal category from my Horizon meter. What I should have reported is as follows:
Channel dbuv
22 56
23 59
25 60
26 62
28 63
These values, which are direct from the aerial, seem to be well over the value predicted by the 'UK digital TV reception predictor' which suggests the normal value to be 46. So, it looks like there is nothing wrong with my setup. I have now removed the attenuator and a couple of splitters I had in my system. The readings after the signal has been distributed by the Labgear splitter are as follows:
Channel dbuv
22 63
23 64
25 65
26 66
28 67
The SN readings from the Horizon meter are showing no errors.
I telephoned Horizon and spoke to a very helpful chap who indicated that HD reception will never give the same signal qualities as standard channels - he said that some meter manufacturers fiddle the signal scale for HD channels to make it seem that the signal qualities are the same for standard and HD channels. He thought that a signal quality for HD of 60% compared to 100% for standard channels is about right.
Does all this make sense to you?
Tony
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jb38: Thank you, again, for a detailed response.
I don't have a HDTM-T2 monitor and I cannot check the HD signal strength except by using what WMC reports. The Horizon expert indicated to me that I should not expect a signal quality of 100%, as, he says, no-one will get that for HD for freeview terrestrial. I cannot comment on whether or not this is really so.
The issue you mention about the BGT3620 card isn't as problem with the card but a 'feature' of WMC for Windows 7 where WMC scans and loads channels from multiple transmitters. This means that there may be several sources for each channel. It then is necessary to manually remove all sources that reference frequencies for transmitters that you don't wish to use. This process is incredibly tedious. As it happens, I am a .NET developer and have written a windows application to manage this issue very easily - it removes all sources whose signal quality falls below a user defined threshold in less than a second. So I have overcome this issue.
Anyway, the main thing is that I do appear to be getting a better than adequate signal from Crystal Palace and do not need to call in a TV engineer.
Thanks for all your help.
Tony
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Nick & Mike: Thank you for your comments.
Like youselves, I am also a bit of a perfectionist (which drives my better half mad). My current Horizon meter seems to be showing that my SD reception is execellent, but in signal strength and quality. The only issue is whether or not my HD reception is optimal. But I don't see how I will be able to prove that without spending a fair amount of dosh getting a HD-T2 meter. The trouble being that once I've established the facts, the meter will be redundant.
The alternative is to get a TV engineer in, and I've been stung doing that before....
Tony
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jb38: This strand really got going because I was wondering why WMC was reporting HD channels as having a signal quality of 60% when all of the SD channels were 100%.
I am committed to providing digital tv to all rooms in my house from a single source. This allows us to be able to watch our recorded tv programs from any room in the house as well as live HD tv without having to replace all of the televisions.
Based upon your suggestions, if there is a problem with the video cards, then I will just have to live with that until a better card comes out.
Hope this thread hasn't been a complete waste of your time and much appreciate your comments and those of other contributers.
Tony
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Sunday 6 May 2012 9:02AM
I use Windows Media Center to access freeview digital services (Crystal Palace) and, since switchover, I'm finding that all of the channels, apart from the HD channels are giving signal qualities of 100% - the HD channels are giving SQs of 60%. Is there any explanation for this variance?
Also, since switchover, I am noticing certain channels, for example BBC News (80), will lose its signal periodically. WMC disables any channels that lose signal quality to zero automatically. So, ,I have to manually re-enable that channel quite often - a real pain.
When I re-enable lost channels and tune in to the channels manually, the signal quality returns to 100%. Go figure. This may be an issue with WMC, but I also think this has something to do with the digital signal after switchover, because this behaviour didn't happen before then.
Has anyone else noticed this or can anyone explain why this might be happening?