Here's your list!
Jeff, I dont think anyone was arguing that a higher bit rate or a different encoding method couldnt affect PQ. Most people were arguing against your original stance, and the question of the poll. Repeaking the dish (if it was already at an acceptable signal level) wouldnt make any difference on the PQ, but would make the signal strength higher.
I wouldn't suggest that re-peaking a dish with "acceptable" signal level would result in an increase in PQ. I would say that the criterion "As long as you have lock" is not good enough. The poll question is merely a vague measure of how common or uncommon in the field, that picture quality has been affected by a re-point. It is assumed there was a problem or you wouldn't be re-peaking the dish.
I will also suggest that digital picture isn't perfect or gone, all or nothing. It does vary, it can be blurry, blotchy, grainy, or lacking detail. Blurry example:
Video Quality Research Home Page
The guy in the following thread describes a compromised digital picture and is told by some, that somehow he wasn't even watching digital anymore - he must be watching analog. He describes poor picture and even ghosting! How could he have seen ghosting? Because the same issues that plagued analog signal are being dealt with in digital signal.
The problems haven't changed, digital is just much more robust in dealing with the interference of multi-path , noise, and the rest. His failing LNB allowed him to watch his digital picture degrade to analog quality. And, we get an interesting glimpse of digital picture variation.
http://www.satelliteguys.us/dish-network-forum/119895-picture-quality-changed.html
Picture quality does indeed vary. So, the question is: "What can an installer due to affect picture quality?"
First, here's what the installer has NO control over. The installer has no way to affect intrinsic noise levels or compression artifacts.
The installer
does have the ability to limit external noise. The installer does have the ability to affect the signal-to-noise ratio, bit error rate, and data rate.
Limiting external noise:
Here is an excerpt from Dish Network training regarding connections:
"A small piece braid left wrapped around the center conductor will short out the signal and any power on the line, sometimes enough signal gets through the short to deliver an impaired picture to the TV-- The customer will see a reduced data rate and pixeling of digital video or no signal at all if there was power on the line."
And this from the same training about connections:
"The prep length of the dielectric is set at ¼". Too long can result in the Post not mating to the Port properly - which can cause poor ground continuity and shielding issues i.e. RF Ingress and egress and higher contact resistance which could damage equipment powered through the cable -- The customer could see interference in the picture, slow data due to increased Bit Error Rate, pixeling of a digital picture or as the connection deteriorates, no service at all."
Note: Dish Network training states above, "The customer could see interference in the picture, slow data due to increased Bit Error Rate,...". So when Hemi 6.1 says, "Yea what gives? A Directv or Dishnetwork Tech. can't change bit rates.", I would disagree. Haven't you ever been on a trouble call where the channels changed very slowly and when you checked the signal, it was low? You peak the dish and when you check the channels, now they change in a normal time frame? I have witnessed this a number of times.
And this from Dish Network training about grounding a system. This is one of the reasons to ground:
"Reduces Radio Frequency Interference which can degrade the display of video signals"
The installer, then, can avoid causing slow data and degraded video by:
1. Installing proper fittings, properly prepping the cable
2. Properly grounding the system.
The installer can also affect the most important variable, signal strength.
I can understand why this is hard to grasp. Those of you who doubt this information, are some of the best installers. With your good pointing skills, you wouldn't ever see any of this when a system is installed. But realize that there are a lot of installers that don't have the skills to peak those weak HD satellite signals. Haven't we all been on dish 500 service calls and found very poorly pointed dishes? How can you NOT get decent signal levels on the strong satellites 119 and 110? 
Yet, what I've seen in the field suggests there is a wide range of skills from good, to bad, to ugly!
If one of you were on a trouble call, you would check the signal, and if you knew you could do better, or thought the signal was low, you would just make it right. Right? But with the previous thinking that digital picture suffers no change or degradation, no assessment of picture quality would be made - and any comment made by the customer about picture quality is immediately dismissed. The whole subject is out of sight, out of mind. It goes against what we have been told. It goes against all of our past experience with digital systems. Until the advent of high definition picture quality and a more discriminating eye, the digital "all or nothing" idea was basically true. In practice, all previous comparisons of standard definition digital TV were made versus analog TV. Even the "compromised" digital picture, would it have been witnessed, would have been better than the static, fading and ghosts of traditional analog TV.
But, the greatest determining factor in system function is signal strength. Signal strength is in the hands of the installer. Signal strength determines the functioning of the system, signal quality, BER, etc.Signal quality is evaluated and expressed in signal-to-noise ratio, noise figure, and their digital cousins bit rate, and bit error rate or BER.
From January 2003 High Frequency Electronics Copyright © 2003 Summit TechnicalMedia, LLC:
"One of the changes that modern digital communications systems has brought to radio engineering is the need for end-to-end performance measurements.
The measure of that performance is usually bit-error rate (BER), which quantifies the reliability of the entire radio system from “bits in” to “bits out,” including the electronics, antennas and signal path in between."
Further,
"With a strong signal and an unperturbed signal path, this number so small as to be insignificant. It becomes significant when we wish to maintain a sufficient signal-to-noise ratio in the presence of imperfect transmission through electronic circuitry (amplifiers, filters, mixers, and digital/analog converters) and the propagation medium (e.g. the radio path or optical fiber)." Encyclopedia of Laser Physics and Technology - bit error rate, tester, BERT, data transmission
Note that with a "strong signal" we overcome BER problems. BER is a signal dependent value.
From Encyclopedia of Laser Physics and Technology:
"Even a digital data transmission system is not totally error-free – statistical fluctuations related to noise influences cause a small percentage of the transmitted bits to be corrupted. The average fraction of incorrectly transmitted bits is called the bit error rate."
And
"The maximum capacity of a reliable data transmission system is not reached by keeping the bit error rate at an extremely low level (basically avoiding any bit errors), but by pushing the data rate to a level where some tolerable bit error rate of e.g. 10-12 can be maintained and by detecting and correcting most of the remaining bit errors." http://www.highfrequencyelectronics.com/Archives/Jan03/HFE0103_Tutorial.pdf
With the HD satellites we can't afford a weak point job like those we've seen in the field with the Dish 500. There isn't the ability for the 129 or 118.7 to even hit 100+ on the signal meter like the 119 and 110. So it becomes crucial to get all the signal you can squeeze out of the 118.7 and 129.
Let me reiterate, you guys already maximize the weak signal, but there are a lot of installers having huge problems peaking multi-satellite dishes.
In the context of troubleshooting and service calls, it is important to know that digital picture is NOT all the same. It is important to understand that signal is the key variable and is installer dependent. It is important to know that picture quality can be affected by signal strength.
It is also important to understand that a small increase in signal strength produces a large decrease in bit error rate.
The installers also have control of the TV's user menu at the time of install. There are TV enhancements to turn off, or adjust; as well as picture controls. The minimum that an installer should do is to reduce the contrast to 50 to 60, reduce sharpness to zero, and turn off "Vivid" or "Dynamic" settings in favor of the "Default" or "Normal" settings. In a dark room or a dedicated theater room, use the "Cinema" setting.
So, if you've used the right cables, made the right connections, enabled the correct (HD) resolution on the receiver, adjusted the TV's enhancements and picture controls, and peaked the HD satellite signal, you'll have the full PQ list and there WILL be a fine picture, and no complaints. There's your list.
The real issue is that complaints of picture quality are everywhere. We are all wanting to assist others in getting the best quality HD available. Without the understanding that digital picture quality isn't always perfect, and without the understanding of what makes the "perfect" picture, our only option is to tell the customer, "No, it couldn't be your signal. Digital is "all or nothing". As long as you've got lock..." You know the rest.
Signal and HD
