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Poor HDTV signal strength on HD-3000
http://forums.linhes.org/viewtopic.php?f=15&t=4418		 Page 1 of 1
Author:  cornrow [ Wed May 04, 2005 4:38 am ]
Post subject:  Poor HDTV signal strength on HD-3000
Hello,

I just spent 11 hours getting this Myth box to the stage it's at, and I still haven't seen the first glimpse of TV. I set up the DVB drivers for my HD-3000, and got to the channel scanning. It finds the correct channels, but at best the signal strength oscillates between about 25% and 50%, usually on the lower end of that. I plugged my regular HDTV receiver into the same antenna without moving it and got 80%+ reception on all the same channels.

Any ideas?

Ty
Author:  Greg Frost [ Wed May 04, 2005 4:46 am ]
Post subject: 
The inside of a computer can be a nasty place for RF interference. The first analog card I had (a pixelview pv-bt878p+) was unwatchable with the signal level at my antenna outlet wheras the TV looked quite alright plugged into the same outlet. I bought a cheap 12 dB RF amplifier to boost the signal before it entered the harsh environment of the PC and lo and behold the signal looked great.

It is worth remembering that a settopbox is designed specifically for the task of reciving rf signals wheras a general purpose computer is not.
Author:  Girkers [ Wed May 04, 2005 7:38 am ]
Post subject: 
Greg sorry to dispell your ideals, but I have done a test on this. With the exact same hardware I install Windows XP and download the current driver and application for my DVB-T card.

I get a signal strength of 77% and SNR of 89%

With MythTV when I scan the channels I get a signal strength of around 30% with a SNR of about 38%

Exact same hardware, exact same location, explain that :P

Sorry I am being a smart arse and that isn't very nice. What I put it down too is drivers.

Obviously with hardware most companies don't develop linux drivers and as such this is left to open source developers who have to do a lot of "guess" work.

With my particular situation I plan on replacing my coax cable with RG-6 and F-type connectors to lessen the signal loss from my aerial.
Author:  brendan [ Wed May 04, 2005 7:46 am ]
Post subject: 
Girkers wrote:
I get a signal strength of 77% and SNR of 89%

With MythTV when I scan the channels I get a signal strength of around 30% with a SNR of about 38%

Exact same hardware, exact same location, explain that :P


Well...one or the other driver itself might be misreporting the numbers from the DVB-T card.

And, for the record, my 3000 also shows abysmally low #s, even with an outside antenne. Still working on that...

-brendan
Author:  Xsecrets [ Wed May 04, 2005 7:49 am ]
Post subject: 
well you could try the old non dvb drivers. I've found that I have problems with the dvb drivers.
Author:  Girkers [ Wed May 04, 2005 8:16 am ]
Post subject: 
brendan wrote:
Well...one or the other driver itself might be misreporting the numbers from the DVB-T card.

-brendan


I thought that too, but when I watch HD with Windowz install it worked fine, with KnoppMyth it is pixelated.

I would try any driver that would work better, but I have a Visionplus using a Connextant Fusion 878A chip.
Author:  Xsecrets [ Wed May 04, 2005 8:45 am ]
Post subject: 
ahh the driver comment was because the original post had hd3000 in it.
Author:  cornrow [ Thu May 05, 2005 12:18 am ]
Post subject: 
I tried the old version of KnoppMyth with non-DVB drivers, and it is exactly the same. I also tried removing the computer from the rack and moving it away from interference. No luck. I also tried getting an antenna from Fry's, but it seems to be a huge piece of crap. Where can I get an RF amplifier?

Ty
Author:  Greg Frost [ Thu May 05, 2005 2:49 am ]
Post subject: 
I thought that the HD-3000 was a digital TV card. In which case, it should either work or not. If it is marginal you may get pauses and stuttering in the picture. I would not have thought that a reception issue could cause pixellation. Are you referring to some sort of corruption or just the picture quality looks different to that in windows. The windows software may be applying a filter. You could try adding denoise3d in the tv-settings->playback filter settings (i think thats where it is without looking).
Author:  cornrow [ Thu May 05, 2005 3:46 am ]
Post subject: 
No, it doesn't show anything at all. I'm not even at the point where I'm trying to see it in Myth (although I have checked it). I am using dtvsignal, or for the DVB driver version, using the scan tool built into setup. In both cases it shows signal strength of 35% or so at best, which is below the minimum threshold set in Myth of 50, so nothing shows up.

Is it at all possible that this is related to either motherboard (ECS something), Processor (Athlon 64 3200), or Power Supply (Piece of crap 300w)

Ty
Author:  Girkers [ Thu May 05, 2005 4:19 am ]
Post subject: 
I don't know this card, but when I scan for my channels in Myth setup my signal strength doesn't get about 30%, but works fine apart from the pixelation mentioned previously.

Just a suggestion are you putting in a frequency for the transport before you start the scan?
Author:  brendan [ Thu May 05, 2005 8:19 am ]
Post subject: 
cornrow wrote:
Where can I get an RF amplifier?


Heh. I spent a half-day or so researching HDTV RF amplifiers, being somewhat bewildered at the results...only to suddenly realize that I already had two: standard broadcast TV or CATV amplifiers work just fine. After all, it's all RF in the same bands...

[Shorter version: Radio Shack carries them. Search for 'amplifier' and then look at the ones they have for TV/VCR/HDTV etc.]

-brendan
Author:  ceenvee703 [ Thu May 05, 2005 8:25 am ]
Post subject: 
Girkers wrote:
Just a suggestion are you putting in a frequency for the transport before you start the scan?


I know the instructions call for entering a frequency, but if you select "full scan" in one of those channel scan dialogs, you can't enter a transport number to start the scan out with. Should you scan for channels individually?

I can also confirm that, although the channel scan reports pretty low signals, the recording itself seems to turn out OK. Well, as OK as they ever did.
Author:  Greg Frost [ Fri May 06, 2005 2:18 am ]
Post subject: 
cornrow: I see now, in another thread, you have got your TV card working. Was it a reception issue or something else?
Author:  cornrow [ Mon May 09, 2005 12:38 am ]
Post subject: 
I replaced the Motherboard (ECS) and Power Supply (old one), and it seemed to work. I still have a new host of problems, but that one's out of the way.

My hunch is that it was a power issue relating to the motherboard connectors. The old power supply wasn't meant for newer motherboards and needed an adapter to connect the 4 pin one.

Ty
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