|
|
|
|
Why haven't we heard of this before now? One reason that the effects of low signal hasn't been noticed and that has perpetuated the myth, is that when the first systems were put in, the ONLY reference was analog TV. Even a degraded digital picture would look good compared to the analog TV that we were used to viewing. In addition to that, other things have changed considerably - including our perceptions of picture quality. We have a more discriminating eye today. There is now a large variety of quality variances and resolutions from broadcasters to systems. Satellite systems and noise have changed greatly over the past three years. Early satellite systems where very easy to install. They used one satellite and they had one satellite receiver. One satellite was easy to hit and get the strong signal. And, one satellite receiver with the associated wiring and connections generated a low amount of noise as compared with today's installations. Performance (signal quality) is determined by the amount of signal vs. the amount of noise. We want to achieve a high signal strength and a low noise figure. When there is enough signal to overcome enough of the noise, we have a complete "acceptable" digital picture (The QEF condition). That used to be easy to do. In today's installations we have multiple satellites to hit and, unfortunately, many installers lack the skills to properly align a multi-sat dish, leading to poor signal strength. To compound the problem, it takes more information to create an HD digital picture versus an SD digital picture. HDTV picture requires 5 to 6 times the amount of information per second to render the correct result. "And if we are talking data communications, higher resolution means that more information has to arrive at a destination in one second than lower resolutions." MPEG In Data terms http://www.techonline.com/article/pdf/showPDF.jhtml?id=1931023401 Why is this important? In the "old days", with the strong signal (119) and lower noise (smaller systems, simple receivers) there was a large margin of error, and it was easy to get it right. The commonly accepted minimum strength was 70, and that was for SDTV! This is key and it is the real reason that Dish changed the scale. If you had ever noticed, signal meter readings on Dish receivers used to register lower as the model numbers went up. A 311 model for example, would always have the highest signal meter reading in a home and the more advanced the receivers became, the lower the signal would read. Until HD entered the scene, the differences in the signal meter readings were caused by the additional noise sources of added components (DVR, Dual tuner), only. The additional noise drops the signal-to-noise ratio, and therefore, registers lower "signal quality" on the meter. With the addition of HDTV and its need for more information (5 to 6 times more information per second) we see an additional drop in the signal quality meter reading. HDTV requires more signal than SDTV. Therefore, a signal strength of 70 on a 311 would NEVER have been enough for an HDTV tuner! We are now installing systems that have much more noise than they used to have and greater signal demands. Each receiver, splitter, cable, diplexer, and connection contained within the system, all add to noise to the system. Other noise factors such as thermal noise also add to the total amount of noise that is present, and needs to be overcome. Noise from power lines, wireless technology, and increased use of the spectrum contribute more noise today than ever before! The result of more signal needed and more noise to deal with, is that it greatly reduces the margin of error when installing a system. This has resulted in a large portion of America living on the cliff. It is more important than ever to maximize the signal strength and minimize noise where possible. And when it comes down to it, after good grounding and proper connections, there isn't really anything else that we can do to limit noise. The good thing is this: A small increase in signal strength will produce a large amount of benefit as it will increase your signal quality considerably. Small increases in signal strength produce dramatic increases in signal quality! Signal strength dramatically affects your system's performance. If you are here searching for why your TV picture is blurry, blotchy, or grainy, and you don't have all the signal you can get...get it. If your signal was below the green of the signal quality scales (below 70) you will likely see increase in the quality of your picture. (This is one of the reasons that a properly installed ground can affect the performance of a system. If the ground is not installed properly, or left out, those wires become a ground loop antenna! Either you have a newly installed "static" antenna to feed your system noise [NOT GOOD], or you ground it so that it will reduce the noise from RF interference, instead of injecting it into your system.) |
What do you want to know? Ask highdefjeff
Become a part of THE Digital Television Community!
Visit DTVUSA Forum and get the help you need!
|
|
You have a right to an antenna! The rule prohibits most
restrictions that: (1) unreasonably delay or prevent installation, maintenance
or use; (2) unreasonably increase the cost of installation, maintenance or use;
or (3) preclude reception of an acceptable quality signal. Over-the-Air Reception Devices Rule Send questions or comments about this web site.Copyright © 2009 WOWVision! Ministries Last modified: 01/16/10
|
