Kansas Zephyr said:
Digital TV has a cliff.
If you are on the cliff you have THE image. The PQ is the same if you are 1 mile or 1 foot from the edge.
If you are teetering, you have pixelization, blocky, intermittent reception.
If you are off the cliff you have no image.
Beware of the placebo effect.
You know, I'm a bit tired of trying to explain why this idea is so incorrect, at first I was going to let it go; but it being Friday, and the Rays/RedSox game is 'droning' on in the background (GO RAYS), that a bit of brainpower can be dedicated toward a response that is quite a bit more accurate.
Yes, on the 'bulk' side of things, there is a 'digital cliff' so to speak.
As the signal drops toward that 'cliff', the FEC (forward error correction) AND the transmission error scheme ((DVB-S2 in the case of DirecTV's HD or Ka/Mpeg4/SD transmissions), has to work harder in recovering the bits.
All kinds of 'effects' can be seen (or not, as the case may be) as the signal drops towards that 'cliff'. When (and IF) you see it may depend on several factors; first and foremost, if you have been trained or are natively sensitive to the effects. Second, if your display is sensitive in and by itself, allowing you (whether sensitive or not) to readily 'see' the effects easily.
The display factor is increasingly something to think about, as typical consumers continue to purchase what I (and most others who have worked in the field) consider to be abysmal display technologies, such as LCD, Plasma, and DLP types.
Those continue to get better over the years, but don't hold a candle to CRT's. There are at least 2-3 different technologies that MAY be able to give them a run for their money. Give it another 5 years.
Getting back to the basics, though, the computational power of the receivers (really, the Mpeg2/Mpeg4 decoder chip), is the limiting piece. As the decoder has to work harder, such things as 'mosquito noise' and 'mini-macro-blocking', effects that poor displays can either mask (or exasperate) come to the fore.
Now, to get to your (potential) problem; Yes, as the dish 'wobbles' (and yes, I also am in a 'high wind' area, the other day the sway of the 130' Evergreens across the street from my house were, well, jaw-dropping (!). But 1s I don't believe that putting the dish on a roof or other 'high' areas is a very good idea, mine is as close to the ground (just enough to clear the 15' tall holly trees), I haven't had to 'tweak' the thing (an AT9/Sidecar) since some 2-3 months after original installation some 3 years ago.
But I have put both AT9/AU9Slimlines on the top of multi-story apartment buildings. I think the 'vibration' you may be seeing mechanically on the dish, in severe wind loads, may cause problems as I pointed out above (make the error-correction work harder, and cause visible picture artifacts, even with monopoles correctly installed and make the dish as rigid as you can get it.
If you are really in a VERY high wind area, and can't get the dish lower (do to any number of factors), you may take a look at putting it inside a microwave transparent dome (fiberglass). I have several dishes inside such an arrangement here, both for wind but also for rain/snow protection.
New ones are bloody expensive, but as I'm obviously near the ocean, used radomes are easily found in junkyards. If your wind/snow problems are really something to 'write home about', you might take a look at what you can come up with.
FYI, I have some relatives that live in Bar Harbor, been a few years since I visited. I can easily envision their poor dish holding on to the mount for 'dear life' during several goodly storms a year!