Excellent explanation. Thanks.
Fred and
Jack
Antenna Height - Height is restricted to 30 meters above HAAT
(height above average terrain) of 76 meters this can be calculated
here.
»www.fcc.gov/mb/audio/bickel/haat···tor.html
Where it asks this question
(Enter the height (in meters) of the antenna radiation center
above mean sea level (RCAMSL))
Enter your site elevation NOT the antenna radiation center because
you get to go 30 meters above ground level at that point.
ref: Second Memorandum Opinion and Order (paragraph - 66)
Frank
Frank
On 9/30/2010 7:37 PM, Jack Unger wrote:
Fred,
I'm sorry to seem dense but I don't understand your explanation
below. I'd appreciate it if you would re-explain. The FCC said:
"transmit antenna used with fixed devices may not be more than
30 meters above the ground. In addition, fixed devices may not
be located at sites where the height above average terrain
(HAAT) at ground level is more than 76 meters".
I'm trying to reconcile that with your statements. Could you
please re-explain more clearly or by using better actual numbers
(both HAAT at ground level and antenna height above ground)?
Thanks in advance,
jack
On 9/23/2010 4:48 PM, Fred Goldstein wrote:
The rules allow antenna heights up to 30 meters, around 100
feet. One problem with the maximum HAAT limit is that it
applies to the ground height, based on having a 30 meter high
antenna. In other words, the ruling assumed a maximum antenna
HAAT, and then set the ground HAAT to be 30m below that. If
somebody's house is >10m below the limit, then a 10m
antenna should be legal. (The minimum antenna height went
away, since sensing is no longer required. That frankly seems
to be the only major improvement in the rules.)
Brian
From: [email protected]
[
mailto:[email protected]] On Behalf Of Tom
DeReggi
Sent: Thursday, September 23, 2010 7:32 PM
To: WISPA General List
Subject: Re: [WISPA] Transmit Antenna Height
Yeah, that really sucks. Many areas needing served have
thick forest/trees easilly 70ft tall.
A 90ft height, just wouldn't allow enough of the signal to
have open air, and the signal would be going through trees
most of the full path.
In 900Mhz, the difference between having the tower side over
the tree line and below the tree line can be the difference
between a quarter mile coverage and a 7 mile coverage in our
market.
All be it, 700Mhz does have better NLOS propogation
characteristics than 900 does.
I would have liked to see that height doubled.
However, admittedly, it will allow much better spectrum
re-use in areas that have a limited number of channels
available.
Spectrum reuse is one of the best ways to serve more people.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
- ----- Original Message -----
- From: Fred Goldstein
- To: WISPA General List
- Sent: Thursday, September 23, 2010 4:36 PM
- Subject: Re: [WISPA] Transmit Antenna Height
-
- This item alone may be the show-stopper, the poison
pill that makes it useless to WISPs in much of the
country.
- In places where the routine variation in elevation is
more than 75 meters, there will be houses (subscribers)
that are more than 76 meters AAT. I notice this in the
areas I'm studying, both in the east and in the upper
midwest.
- In a place like Kansas, nobody is >75m AAT. But in
the woody Berkshires of Western Massachusetts, the UHF
space is needed to get through the trees, and a
significant share of houses are >75m AAT. Also, if
you want to cover a decent radius, the access point
needs to be up the hill too. 75 meters isn't a
mountaintop; it's just a little rise.
- It makes no sense to absolutely ban fixed use at a
site that is 100m AAT if the nearest protected-service
contour is, say, 50 miles away. A more sensible rule
would be to follow broadcast practice, and lower the ERP
based on height, so that the distance to a given signal
strength contour is held constant as the height rises.
Hence a Class A FM station is allowed up to 15 miles,
and if it is more than 300 feet AAT, then it is allowed
less than the 3000 watts ERP that apply at lower
heights.
- Maybe the lawyers want to have more petitions to argue
over.
- At 9/23/2010 04:07 PM, Rich Harnish wrote:
- 65. Decision. We decline to increase the maximum
permitted transmit antenna height above ground for fixed
TV bands devices. As the Commission stated in the Second
Report and Order, the 30 meters above ground limit was
established as a balance between the benefits of
increasing TV bands device transmission range and the
need to minimize the impact on licensed services.129
Consistent with the Commission’s stated approach in the
Second Report and Order of taking a conservative
approach in protecting authorized services, we find the
prudent course of action is to maintain the previously
adopted height limit. If, in the future, experience with
TV bands devices indicates that these devices could
operate at higher transmit heights without causing
interference, the Commission could revisit the height
limit.
-
- 66. While we expect that specifying a limit on antenna
height above ground rather than above average terrain is
satisfactory for controlling interference to authorized
services in the majority of cases, we also recognize
petitioners’ concerns about the increased potential for
interference in instances where a fixed TV bands device
antenna is located on a local geographic high point such
as a hill or mountain.130 In such cases, the distance at
which a TV bands device signal could propagate would be
significantly increased, thus increasing the potential
for interference to authorized operations in the TV
bands. We therefore conclude that it is necessary to
modify our rules to limit the antenna HAAT of a fixed
device as well as its antenna height above ground. In
considering a limit for antenna HAAT, we need to balance
the concerns for long range propagation from high points
against the typical variability of ground height that
occurs in areas where there are significant local high
points – we do not want to preclude fixed devices from a
large number of sites in areas where there are rolling
hills or a large number of relatively high points that
do not generally provide open, line-of-sight paths for
propagation over long distances. We find that limiting
the fixed device antenna HAAT to 106 meters (350 feet),
as calculated by the TV bands database, provides an
appropriate balance of these concerns. We will therefore
restrict fixed TV bands devices from operating at
locations where the HAAT of the ground is greater than
76 meters; this will allow use of an antenna at a height
of up to 30 meters above ground level to provide an
antenna HAAT of 106 meters. Accordingly, we are
specifying that a fixed TV bands device antenna may not
be located at a site where the ground HAAT is greater
than 75 meters (246 feet). The ground HAAT is to be
calculated by the TV bands database using computational
software employing the methodology in Section 73.684(d)
of the rules to ensure that fixed devices comply with
this requirement.
-
- 130 The antenna height above ground is the distance
from the antenna center of radiation to the actual
ground directly below the antenna. To calculate the
antenna height above average terrain (HAAT), the average
elevation of the surrounding terrain above mean sea
level must be determined along at least 8 evenly spaced
radials at distances from 3 to 16 km from the
transmitter site. The HAAT is the difference between the
antenna height above mean sea level (the antenna height
above ground plus the site elevation) and the average
elevation of the surrounding terrain.
-
- 67. In reexamining this issue, we also note that the
rules currently do not indicate that fixed device
antenna heights must be provided to the database for use
in determining available channels. It was clearly the
Commission’s intent that fixed devices include their
height when querying the database because the available
channels for fixed devices cannot be determined without
this information.131 We are therefore modifying Sections
15.711(b)(3) and 15.713(f)(3) to indicate that fixed
devices must submit their antenna height above ground to
the database.
-
- 68. We continue to decline to establish height limits
for personal/portable devices. As the Commission stated
in the Second Report and Order, there is no practical
way to enforce such limits, and such limits are not
necessary due to the different technical and operational
characteristics of personal/portable devices.
- --
- Fred Goldstein k1io fgoldstein "at" ionary.com
- ionary Consulting http://www.ionary.com/
- +1 617 795 2701
-
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ionary Consulting
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Jack Unger - President, Ask-Wi.Com, Inc.
Author - "Deploying License-Free Wireless Wide-Area Networks"
Serving the Broadband Wireless, Networking and Telecom Communities since 1993
www.ask-wi.com 818-227-4220 [email protected]
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Jack Unger - President, Ask-Wi.Com, Inc.
Author - "Deploying License-Free Wireless Wide-Area Networks"
Serving the Broadband Wireless, Networking and Telecom Communities since 1993
www.ask-wi.com 818-227-4220 [email protected]
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