Frank, et al,
I just did a calculation for the -38 dBm contour for a full power DTV broadcast station. -38 dBm - 33 dB = -71 dBm, it sure looks to me like a 40 mW TVBD inside 1500 feet could be a problem. Anyone care to comment?
I reviewed the new regulations today and it looks like the power levels will not exceed +26dBm EIRP, and limits on PFD are set in the new regulations, which I believe, is a good bit lower than that permitted in the 900 MHz band. Remember that each of the TV Channels is only 6 MHz wide as compared to wider channel(s) in 900 MHz.
I got some satisfaction in seeing limits on power on adjacent channels, both in absolute power and relative power based on incumbents. That comforts me a bit related to OTA broadcasts. I haven't done a C/I calculation yet. I hope it beats the number Feory's provided, at minimal distances.
My work is related to wireless broadband, but this potential to harm OTA has really concerned me, maybe just on principal.
I did a quick link budget calculation and it looks like 2 miles will be about it.
Now that I've seen the Second Memorandum Opinion and Order, I'd say it leaves plenty of margin for your TV -- even if you have your own white spaces device (TVBD) and set it right on top of your TV set.
With the contours of an adjacent TV station, TVBDs are limited to 40 mW = 16 dBm. TVBDs are also required to reject adjacent channel emissions to at least 72.8 dB below their max average operating power.
So in the worst case, you have -56.8 dBm of interference power at the edge of the adjacent (desired) TV channel. Your DTV receiver already tolerates interferers larger than this.
Like most death nails this one is probably just helping it along. The final one will be when convergence on seeing video on all computer devices happens. The technology could in place now, but when greed, lawsuits, and politics get involved don't hold your breath for that last nail.