At 10/1/2010 05:47 PM, you wrote:
Eudora! Now there is a program I havent seen in years!
Four years discontinued, there's still nothing as good out there to
replace it (on Windows).
On Fri, Oct 1, 2010 at 2:56 PM, Fred Goldstein
<<mailto:fgoldst...@ionary.com>fgoldst...@ionary.com> wrote:
At 10/1/2010 02:27 PM, Matt Jenkins wrote:
What are the headings for your chart? I don't understand it....
Eudora had trouble with cut-and-paste of the original document.
The first column is height above average terrain, from x to y meters
(10 but less than 30, from 30 but less than 50...). The second is
the proposed distance outside of the protected contour of a
co-channel station. THe second (the small distance) is the proposed
distance outside of the protected contour of an adjacent-channel station.
So IEEE 802's proposal (in a 2009 Petition) was to allow antennas
above 600 meters HAAT only if more than 68 kilometers outside of the
protected contour of a co-channel station, or 426 meters outside of
the contour of an adjacent-channel station.
Not that those calculations were perfect; sometimes being precise
isn't the same as being accurate. TV broadcast interference is
usually measured at a fixed height, I think 10 meters above
ground. If the antenna is 500m above average terrain, it is
probably more than 30 meters above ground. It might even be on a
rather tall tower. In that case, the signal level near the ground
will not be the same as the signal level in a straight line. So
there is probably no likelihood of adjacent-channel interference.
I remember an FM station (WMSC) that came on the air around 1970, 2
channels away from two another ones (WKCR, WFUV) whose protected
contours it was within. You had to protect second and third
adjacent channels, which normally meant 4-channel spacing, because
receivers near to the antenna would be clobbered (>20dB
stronger). In this case the new station was about halfway up an
existing 1000-foot TV mast. So its signal strength at the height
that counted was so low that it did not violate the interference
rules for second and third adjacent channels. It is currently
licensed for 1W ERP at 205m HAAT. (But one of the
second-adjacent-channel licensees has still given them grief at the FCC.)
--
Fred Goldstein k1io fgoldstein "at" ionary.com
ionary Consulting http://www.ionary.com/
+1 617 795 2701
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