<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div dir="ltr" id="yui_3_16_0_1_1413253379410_5065"><span id="yui_3_16_0_1_1413253379410_5768">I get that. What I'm not sure about is what kind of signal strength I'm looking for. Do I want a higher signal strength, or do I want it as close to 1 or 0 as possible? What about signal to noise ratio? I read somewhere that around 35 dB is optimal. That seems a bit arbitrary.</span></div><div id="yui_3_16_0_1_1413253379410_5769" dir="ltr"><br><span id="yui_3_16_0_1_1413253379410_5768"></span></div><div id="yui_3_16_0_1_1413253379410_5770" dir="ltr"><span id="yui_3_16_0_1_1413253379410_5768">Also, looking at the numbers for my channels, I don't see anything that stands out that would make one channel worse than another. The signal strengths and S/N ratios are all very close. Could there be another cause?</span></div><div dir="ltr"><br><span id="yui_3_16_0_1_1413253379410_5768"></span></div><div dir="ltr"><span id="yui_3_16_0_1_1413253379410_5768">Mike</span></div> <div class="qtdSeparateBR"><br><br></div><div style="display: block;" class="yahoo_quoted"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"> <font size="2" face="Arial"> On Monday, October 13, 2014 9:28 PM, Stephen Worthington <stephen_agent@jsw.gen.nz> wrote:<br> </font> </div> <br><br> <div class="y_msg_container">On Tue, 14 Oct 2014 15:00:50 +1300, you wrote:<br clear="none"><br clear="none">>On Tue, 14 Oct 2014 00:49:23 +0000 (UTC), you wrote:<br clear="none">><br clear="none">>>I've finally gotten my Ceton InfiniTV 4 PCie working on Mythbuntu. <YAY!> Anyway, I've set up a bunch of shows to record, all of them HD. Many of those shows record just fine. However, I'm a racing fan, and every race I've recorded so far has been of really poor quality except one.<br clear="none">>><br clear="none">>>All of those recordings show up with a yellow border. I think that means the recording is damaged from what I've read. When I watch the recording, every time a scene changes, the screen gets very blocky (macroblocking?) and the audio cuts out, then it will return to a beautiful recording for a moment until the camera changes, then it repeats. It gets worse and worse as the show goes. I haven't let it run, but I have noticed that the file size is very small. For example, a normal TV show recorded for 1 hour at 5.xx Gb. A formula 1 race (3 hours) recorded at 0.5 Gb.<br clear="none">>>I've also had some problems with BBC America. Some recordings are great. Some show up as yellow like the races. Of those, some just hang the frontend. Others come back with a message saying the file is missing.<br clear="none">>><br clear="none">>>The one race recording I recorded without problem was a NASCAR race that was not scheduled to record, but I turned it on in Live TV. It looked great, so I went back to the program guide and tried recording it. It recorded fine. As I said, these shows are all HD.<br clear="none">>> Initially, I was unable to record anything when I set up the box. I was getting buffer errors. I found that my network was running at 10Mb/s. I fixed that so it's running at 1000MB/s, but I still have some Cat5 (not 5e) cable in the walls.<br clear="none">>>I looked at the channels that I've recorded on and here's what I got for signal strength and S/N ratio:TNTHD - always good: Signal Strength - 3.8 dBmV, Signal to Noise Ratio - 32.6 dBWMAQHD - always good: Signal Strength - 4.1 dBmV, Signal to Noise Ratio - 33.4 dBWBBMHD - always good: Signal Strength - 5.9 dBmV, Signal to Noise Ratio - 34.6 dB<br clear="none">>>BBCAHD - sometimes good recordings, other times not: Signal Strength: 2.3 dBmV, Signal to Noise Ratio: 34.1 dBNBCS1HD - always bad: Signal Strength - 3.9 dBmV, Signal to Noise Ratio - 34.8 dBFS1HD - always bad: Signal Strength - 3.5 dBmV, Signal to Noise Ratio - 32.1 dB<br clear="none">>>Since it seems like a channel thing (higher channels have problems, lower channels don't), I figured I'd look at improving my signal strength. I've had a Motorola 1-2 amplified splitter (<a shape="rect" href="http://www.amazon.com/Motorola-Signal-Booster-BDA-S2-Amplifier/dp/B0017I1PVC/ref=pd_sim_e_5?ie=UTF8&refRID=0REJCWJTGHQ0WF945342" target="_blank">http://www.amazon.com/Motorola-Signal-Booster-BDA-S2-Amplifier/dp/B0017I1PVC/ref=pd_sim_e_5?ie=UTF8&refRID=0REJCWJTGHQ0WF945342</a>) on the line coming into my house for a while now. It helped a lot as before I couldn't tune. I've got one of those lines going to my old STB, and the other going to a 1-2 splitter. From the splitter, one line goes to the cable modem, and the other line goes to my backend's cable tuner card. I've always read that splitters degrade signal, so I tried disconnecting the STB and connecting one long line directly from the Motorola amplifier to my cable card. On all channels, SS goes up by 2 - 3 and S/N goes up a bit too. I've read that a perfect signal strength would be 0 dBmV, but I'm wondering if that's wrong.<br clear="none">>>Can anybody offer any suggestions on what I should look at to be able to record these shows?<br clear="none">>>Mike<br clear="none">><br clear="none">>Basic physics applies to splitters, as in all things. If you split a<br clear="none">>signal into two, then each split signal will be less than half the<br clear="none">>signal strength of the incoming signal. The "less than" bit is due to<br clear="none">>whatever losses occur in your splitter - some are much more lossy than<br clear="none">>others. The only reason that splitters work in aerial systems is that<br clear="none">>tuners usually have a very wide range of signal strength that they can<br clear="none">>work with, so halving the strength in a two-way splitter still leaves<br clear="none">>a signal that is easily enough for a tuner to work with.<br clear="none">><br clear="none">>When your signal strength as received at the aerial is too low but of<br clear="none">>OK quality, or you are reducing the strength by using splitters,<br clear="none">>amplifying it helps reception. But if the signal strength at the<br clear="none">>aerial is so low that the quality of the received signal is not good<br clear="none">>enough for the tuners to use, amplifying it does not help, and in fact<br clear="none">>degrades the signal quality further as amplifiers are not perfect.<br clear="none">><br clear="none">>Aerials are a compromise - they normally have one frequency they work<br clear="none">>best at and their performance drops off the further away from that<br clear="none">>frequency a channel is being transmitted on. So higher and higher<br clear="none">>frequency channels (in your case) will likely be getting lower and<br clear="none">>lower quality as received by the aerial, even if they are all<br clear="none">>transmitted with the same strength and quality. Which they are not -<br clear="none">>transmitters vary in quality and transmission power, even when all<br clear="none">>your channels are transmitted from the same site. Aerials are also<br clear="none">>more or less directional - if your channels are transmitted from<br clear="none">>different sites, your aerial will likely be pointed in a compromise<br clear="none">>direction somewhere between the transmitters.<br clear="none">><br clear="none">>So, as you can see, aerial systems can become very complicated. I<br clear="none">>would suggest that the first thing to find out is if the quality of<br clear="none">>your signal for the bad channels is good enough to work with at all.<br clear="none">>That means plugging your aerial signal as directly as possible onto<br clear="none">>one tuner without any splitters (or amplifiers initially). Can you<br clear="none">>record from it then? You may need to try adding amplification, but no<br clear="none">>splitting. If that works, then you can probably organise amplifiers<br clear="none">>and splitters that will work. But if it does not work, then the<br clear="none">>problem is the aerial itself. You may need a different aerial to pull<br clear="none">>in the problem channels, for example, one aerial pointed in the<br clear="none">>direction of each transmitter site and selected for the frequencies<br clear="none">>involved.<br clear="none">><br clear="none">>If the quality is OK with just one tuner on the aerial, then you may<br clear="none">>need to get a better signal path from the aerial to your tuners. The<br clear="none">>ideal setup with amplifiers is to have one amplifier/splitter at the<br clear="none">>aerial or as close to it as possible (eg where the aerial cable enters<br clear="none">>the house). That amplifier/splitter would have individual aerial<br clear="none">>cables going from it to every tuner (including your TVs). Also,<br clear="none">>amplifiers and splitters come in widely varying quality - choosing<br clear="none">>good ones is important when dealing with lower quality signals. It<br clear="none">>really helps to have a professional quality signal meter when setting<br clear="none">>up aerial systems like that, and some experience with aerials - so if<br clear="none">>you have a good aerial company you can hire to do the job, that may be<br clear="none">>the best option. There seem to be plenty of bad aerial companies<br clear="none">>around though.<br clear="none"><br clear="none">Oops, I did not read your email thoroughly enough - you are on cable,<br clear="none">not an aerial. The same rules apply though - the signal at the end of<br clear="none">the cable has to be good enough quality for an amplifier to work, so<br clear="none">try a direct path with no splitting to one tuner. If that does not<br clear="none">work, then you will likely need to get your cable company to fix the<br clear="none">signal. However, on looking at the infiniTV 4 PCIe card on the Ceton<br clear="none">web site, it looks like it only has one cable input. Since it clearly<br clear="none">has four tuners, it must contain a four way splitter. Possibly it may<br clear="none">also have an amplifier to make up for the splitter, but even if it<br clear="none">does, the signal quality at each of the four tuners will be less than<br clear="none">it is on entry to the card. So you may find that a single tuner cable<br clear="none">card can pull in your bad channels, where a four tuner one can not.<div class="yqt8381125910" id="yqtfd10483"><br clear="none">_______________________________________________<br clear="none">mythtv-users mailing list<br clear="none"><a shape="rect" ymailto="mailto:mythtv-users@mythtv.org" href="mailto:mythtv-users@mythtv.org">mythtv-users@mythtv.org</a><br clear="none"><a shape="rect" href="http://www.mythtv.org/mailman/listinfo/mythtv-users" target="_blank">http://www.mythtv.org/mailman/listinfo/mythtv-users</a><br clear="none"><a shape="rect" href="http://wiki.mythtv.org/Mailing_List_etiquette" target="_blank">http://wiki.mythtv.org/Mailing_List_etiquette</a><br clear="none">MythTV Forums: <a shape="rect" href="https://forum.mythtv.org/" target="_blank">https://forum.mythtv.org</a></div><br><br></div> </div> </div> </div> </div></body></html>