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| Strong Signal, Poor Reception http://forum.linhes.org/viewtopic.php?f=6&t=17047 |
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| Author: | bobaloo4200 [ Sun Oct 21, 2007 4:18 pm ] |
| Post subject: | Strong Signal, Poor Reception |
I am running R5F27 with a pcHDTV-3000. I have been able to successfully get an OTA signal for years with this card. I recently moved into a basement dwelling, so I've decided to try and use my QAM reception from cable. I can successfully tune QAM channels with my TV tuner, so I know they're there. I ran the myth tv channel scanner and it found all of the channels that I get on my TV. The problem is when I watch tv, I get a full signal (~80-90%) but the picture comes in as one broken up frame every second or so. It looks like I have no signal. The same thing happens when I record without watching tv and play it back. When you first select the "Watch TV" option, the OSD shows: Signal 89% | S/N 3.9db | BE 0 | (L__) Partial Lock then slowly the rest fills end until I'm locked; Signal 89% | S/N 3.9db | BE 0 | (LAM) Lock top shows less than 50% cpu load and the swap not being hit at all. I am able to watch videos through myth video. I also ran azap and was able to get a clear picture, so I'm thinking it's myth related. I've tried setting up myth backend with all the different frequency table variations: cable, HRC, and IRC; and the vanilla "cable" setting seems to be my deal. I've dug around in the frontend and backend logs and nothing jumped out at me, however I'm not sure what I'm looking for. I've searched around the forums and am having difficulty find someone with similar issues. If any one could provide guidance, it would be much appreciated. -bobaloo4200 |
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| Author: | bobmyth [ Sun Oct 21, 2007 6:00 pm ] |
| Post subject: | |
Do not watch the show while it is recording, but only after the recording has finished. A friend of mine has used this method to crutch along, I'm curious if it will work for you. I'm not sure what the conflict is. He, too, always used the card for OTA until recently. |
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| Author: | nbdwt73 [ Sun Oct 21, 2007 8:27 pm ] |
| Post subject: | |
What are your system specs (CPU, memory type and size). |
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| Author: | Girkers [ Sun Oct 21, 2007 8:37 pm ] |
| Post subject: | |
bobaloo4200, the problem could be the S/N. This is the signal to noise ratio in that the amount of signal compared to noise, the higher the figure the better, meaning you are getting more signal than noise. Whilst you are getting a good signal strength of 89% a lot of that is noise as the gap between the signal and the noise is 3.9db. Have you tried a different cable as this could sometimes be the problem. It is a similar problem people have with there ADSL connections in that it drops out or doesn't work very well as the S/N (sometimes SNR) is very low. You need to improve the S/N to help "clean" up the signal. |
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| Author: | bobaloo4200 [ Mon Oct 22, 2007 5:17 pm ] |
| Post subject: | |
Hi all - Thanks for the responses. First off, for those curious my system specs are:
768 MB RAM Seagate 250GB EIDE HD Mach Speed P4MSD-800 Socket 775 Motherboard XFX GeForce FX 5200 128MB DDR 8X AGP pcHDTV-3000 Tuner Card Like I said, I'm doubtful that it's hardware related as I have had this rig running successfully for over a year now. I had everything working OTA, but am trying to get QAM working because I have a poor reception in this basement apartment. I tried swapping out my coaxial cables to see if the S/N changed. It didn't between cables. As another test, I hooked up my antenna again using the same cable (for distance reference: my antenna is physically less than a foot from the cable jack, so it's not like I'm laying out my cable in two physically different spots) and everything worked perfectly (other than poor reception). The S/N did change slightly (down to 3.3db from 3.8 ), but not enough to explain the night and day difference in picture quality. I'm really thinking this is software related as I can use azap to capture video outside of myth and it looks fine. Something happens in myth to cause the recordings to breakup. I've tried changing the card type in mythtv-setup from DVB to "pcHDTV DTV Capture Card (w/4VL drivers)", but that just made it not work at all. Could the frequency table variations be causing it? I've tried all versions and I only got hits with cable-us, so I'm thinking that's where I'm supposed to be; but could be wrong. Yeah, so to sum up, I know the cable signal is unencrypted because I can tune it on my television tuner. I can capture video outside of myth using azap. My scan finds all the channels it should with a very strong signal (>85%). When I record (even without watching) the picture is extremely choppy (in fact my OTA reception with signal strength of 20% is less choppy than the QAM reception). Any further advice is greatly appreciated. -bobaloo4200 |
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| Author: | bobaloo4200 [ Sat Nov 03, 2007 3:05 pm ] |
| Post subject: | |
Hi all - I'm still having difficulties with this. Does anyone have any other ideas for where I could troubleshoot? Thanks. |
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| Author: | Liv2Cod [ Sat Nov 03, 2007 8:25 pm ] |
| Post subject: | |
This may sound weird but your signal may be TOO strong. If you have a splitter or something that attenuates the signal, try putting it in front of the tuner card. If the signal is too strong, the card may be compressing it which would ruin the modulation. I've never seen a signal even close to 80% on my pcHDTV cards so I can imagine a 90% or better signal is pretty darned strong. |
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| Author: | auttila [ Sun Nov 04, 2007 1:06 am ] |
| Post subject: | |
An antenna amplifier can indeed ruin the signal. The strength goes to top and the quality hits the bottom. Check if your antenna amplifier has an adjustment screw. I have 56% signal on my DVB-T cards, and have had no problems. |
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