Just as fast as any other frequency.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
On 9/24/2010 5:50 PM, RickG wrote:
But how fast can 200 or 300MHz go?
On Thu, Sep 23, 2010 at 7:41 PM, Brian Webster
<bwebs...@wirelessmapping.com <mailto:bwebs...@wirelessmapping.com>>
wrote:
But what if you are able to use spectrum around 200 or 300 MHz?
That certainly goes through trees.
Brian
*From:* wireless-boun...@wispa.org
<mailto:wireless-boun...@wispa.org>
[mailto:wireless-boun...@wispa.org
<mailto:wireless-boun...@wispa.org>] *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 <mailto:fgoldst...@ionary.com>
*To:* WISPA General List <mailto:wireless@wispa.org>
*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
<http://ionary.com>
ionary Consulting http://www.ionary.com/
+1 617 795 2701
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