Just thought I'd post this if anyone is interested. If anyone is living close to a windfarm they might want to read this.
Most of the article relates to NTSC, so I've only included text that relates to DTV
from: EFFECTS OF WINDMILLS ON TELEVISION RECEPTION
Most of the article relates to NTSC, so I've only included text that relates to DTV
from: EFFECTS OF WINDMILLS ON TELEVISION RECEPTION
<edited to remove sections unrelated to DTV>
...
WILL HDTV BE AFFECTED?
So what happens when we switch from NTSC to HDTV over‐the‐air transmission? Will the potential for interference from wind turbines still exist?
To date, no signal quality tests have been conducted to determine the impact from wind turbines on HDTV signals because currently, there are no large‐scale wind farms in proximity to any of CBC’s existing HDTV transmitters. However, based on previous work with NTSC signals, it can be theorized that interference may occur.
HDTV receivers have built‐in ghost‐cancelling circuits not found in NTSC receivers. These circuits should greatly reduce or even eliminate the static interference created by larges structures such as wind turbines. Therefore, it is expected that HDTV will be more immune to the static effects from the wind turbines.
Dynamic interference, however, is a different story. As noted earlier, dynamic interference results when the receiver sees not only the main signal but also one or more additional signals reflected off the rotating blades of the wind turbines. As the signal is only reflected when the blades are at a particular point in their rotation, the reflected signal causes a sudden increase or
decrease in the amplitude of the received signal, in sync with the rotation of the blades. HDTV, like NTSC, uses amplitude modulation and so it is possible that HDTV signals may experience dynamic interference. Unlike NTSC, though, this interference may show up as pixelisation, blocking, frozen frames or the complete failure to decode.
It is likely that the degree of impact caused by any dynamic interference to HDTV signals will be related to the quality of the ghost‐cancelling and Automatic Gain Control (AGC) circuits in the receiver. These may vary from one receiver to the next as the performance of the ghostcancellation
circuits is a Consumer Electronics manufacturer proprietary issue. However, the actual degree of interference to our HDTV signals will not be truly known until field measurements are completed. Although the CBC fully expects to undertake these measurements when an HDTV transmitter is installed near a wind farm, this will likely not occur for a few years yet, and it is acknowledged that advances in receiver technology and design may overcome these issues before any measurements are taken.