On April 12, 2000 as the weather began to move
into spring, Mike Willett, our NSF project technical assistant
from Dallas, and I, as Principal Investigator from Colorado Springs,
rendezvoused at Trout Lake, northwest of Rhinelander, Wisconsin,
to accomplish several things.
1. Make a joint decision, with Tim Kratz, Site Manager, for
North Temperate Lakes Long-term Ecological Research Site at the
University of Wisconsin, and Joe Sanfillipo of Northern Technical
Services who would do the construction, exactly where to site
the 110 foot tower we had determined, on earlier visits, would
be required to enable FCC Part 15 type data radios to link up
both to a higher tower on Muskie Mountain, and to close in Data
Collection sites near or on Trout Lake itself.
2. Make a decision through consultations with
Tim Kratz, Paul Hanson, Technological Manager of the University
of Wisconsin Center for Limnology in Madison, and technical and
support staff of Trout Lake, what the exact architecture of the
wireless data collection network should be, and how it will interface
with both Trout Lake Station, the Madison Center, and the Internet
3. Do a series of field tests of the radios
we had selected to be the backbone of the network, to both get
a rough 'benchmark' for the ability of these radios to penetrate
the mix of deciduous and pine trees that exist throughout the
research area as forests, and to map out a profile of the areas
radiating outward from the Research Station that could be reached
directly by these radios, without using radio relay stations.
4. Get, install on our own computers, both
the Campell Scientific software that the Center uses to control
their Campbell Data Collectors - principally the CR21X's which
are used to collect data from a complete weather/water station
on a raft on Sparkling Lake, the unique, compiled, programs created
at the Station that runs on the CR21Xs there, and become intimately
familiar with the LTER's data collection procedures, and how the
data is stored, and communicated to Madison. In this, Tim Meinke,
the Station's long time chief Technician would be the key man
to work with.
5. Become familiar with the $83,000 data collecting
'Apprise Buoy' that the Station had recently acquired with an
NSF grant, that Paul Hanson was responsible to get operating,
and which he had determined could be connected by advanced wireless
from its place on the water.
In spite of a snowstorm that swept over the
area, dumping 2 inches of snow the night we arrived at the cabins
at the center - after a perfectly beautiful day when we came in
on Wednesday the 21st - we accomplished all the tasks I had set
out for the two working-day trip.
THE LOW-COST WIRELESS CHALLENGES
In previous reports - which can be accessed
under the Progress Reports section - Reports
4 and 6 - the geographical layout of the Trout Lake Research Area
is described, accompanied by maps and photographs. I won't repeat
Suffice it to say that the main characteristic
of the Research Area, currently embracing 7 lakes and bogs, the
furthest of which is only 3 miles from the Research Center on
the southern end of Trout, the largest, lake - are the forests.
Distance, or range, for the data radios to
traverse is not a problem. The entire area can easily be reached
by almost all Part 15 radios, operating at, from 100 milliwatts,
to 1 watt, of power. The problem is the uniform coverage of the
entire area by tall trees, whose branches and leaves will sharply
reduce, with wide variations caused seasonally, the useful range
of the radios that are sited to penetrate them parallel to the
The technical reasons that thick stands of
trees are a challenge - which for environmental biological field
science areas throughout the world are to be expected - are twofold.
First, the current FCC Rules for use of Part 15 no-license radios,
particularly spread spectrum radios limit the devices to a maximum
of 1 watt of radiated power at the radio, and no more than 36dB
of radiated power gain at the associated antennas in the US. (it
is as low as 100milliwatts in numerous other countries.) The second
reason is that no-license radios whether spread spectrum in design,
or under UNII rules, are currently confined by the FCC to three
frequency bands which are relatively high on the spectrum of usable
frequencies - 902-928Mhz, 2.4-2.483Ghz, and 5.725-5.85Ghz. This
means they must - as a function of both power and frequency -
operate pretty much as 'Line of Sight' radios beyond any but the
closest distances - such as inside buildings, or after a few hundred
meters between buildings, or trees. Low power and obstacles, whether
trees or hills, sharply reduce the ability of the radios to communicate
These factors were well known to myself and
radio engineer Mike Willett from our years of experience deploying
such radios, both commercially, and through my findings via the
'Education by Wireless' NSF Grant ANI 9527664, that I supervised
between 1995 and 1999. Just 'how limiting' the specific types
of trees, and their densities in the Trout Lake 'North Temperate
Zone' region would be, was yet to be determined - but it did not
take an elaborate engineering analysis or costly spectrum analyzers,
for us to know that the best strategy for dealing with the trees
that rimmed all the lakes and bogs in the area, was to get above
them at strategic points, striving to get direct sight lines between
the antennas mounted on masts or towers (or even cooperating trees!)
and the data collection floats or devices put on or near the water.
Or, at the very least, by calculating the number of meters or
kilometers of average density trees that a signal would have to
pass through when it comes down from a high point at a slant angle,
stay within the penetrating-power capabilities of the radios to
sustain a link. Another strategy could be the use of radios for
'relaying' signals through forested areas at ground level, or
from various high points.
On prior trips to the region we had decided
that one new tower was needed in the close vicinity of the Research
Station. It would have to be at least 110 feet to comfortable
clear the trees that averaged 85 feet in height. Northern Services
was capable of erecting such a tower under contract to the NSF
Project, but it would have to be guyed both for practical safety
and government regulatory purposes.
THE RESEARCH STATION TOWER
The first order of business on Thursday, the
13th, was to decide on the exact location for the main tower,
and its required concrete base - which could not be emplaced until
the ground had thawed - April at the earliest. Joe Sanfillipo
of Northern had already made two trips to the Station, and discussed
tower locations with Tim Kratz, and had given the Project an estimate
($5,700 for a 110 foot tower). Two possible locations had been
discussed - one right next to the main research center building
at the Center, the other at the far end of the row of cabins on
The Station personnel, headed by Tim Kratz,
were concerned about the environmental impact of the tower - both
its appearance, and the degree to which trees on the property
would have to be trimmed or cut down. While the Trout Lake Research
Center consists of many buildings, and considerable amounts of
equipment and vehicles, care had been taken to make the facility
blend in as much as practicable with the surround sylvan wooded
setting. A tall metal tower would be intrusive. In turn we had
to be concerned about the distance from the nearest building,
for power and antenna cables - which reduce the throughput from
the radios the longer they reach - and the point on the premises
that the data signal can enter the local area network - LAN -
and thus the Internet. So a compromise was indicated.
There was a brief jocular discussion about
camouflaging the tower, and we mentioned the costly Cell Phone
towers on Monument Hill in the midst of the Black Forest along
the Interstate between Colorado Springs and Denver, in Colorado.
They are designed to look as much as possible like, and blend
in with, the surrounding Ponderosa Pines. One has to look for
a few seconds at the structures before one realizes they are not
natural. When passing by at 75mph they do not attract attention
to the man made structures. However they cost $250,000 each. I
mention this, because environmental suitability of antenna towers
- whether in rural natural or urban settings has already become
a legal and regulatory issue at the FCC. Wireless demands towers
and tall antennas. Aesthetics calls for their minimization or
elimination. One solution is to make them blend in better. However
few companies have specialized in that potential market. Other
than possibly painting the 120-foot bright metallic colored tower,
nothing much can be done at Trout Lake to mask the new structures,
which is one aesthetic price of wireless.
After tromping around in the snow for about
an hour, everyone agreed on a third, compromise, location - behind
a garage in what might be termed the 'industrial' area of the
complex. About 100 meters from the main research building, which
would require a link from there to the tower or the radios at
its base. But the main advantage of the site was that there is
one heated room in the garage, where preserved plankton samples
are stored. We could put our small radios in that room, where
there is also 110v wall power, and still only have about 130 feet
of RF cable running to the antennas on top of the mast. (There
is 3-4 dB of loss per 100 feet in even the best RF cables, so
minimizing that loss was a consideration for us.) Joe Sanfillipo
still had concerns about just where he could run the angular guy
wires, which had to be on the garage side of the tower site, and
legally 120 degrees from the other two legs of guy wires. Only
a minimal number of branches might have to be trimmed from the
trees in the woods around the tower, no large trees having to
be cut down. Which was a relief to all.
At first we thought we should dig a 100 meter
ditch through the woods between the garage and the Research building,
to bury CAT5 cable or fiber to link the radio at the base, to
the POP in the main building. But Mike and I decided, later, that,
given the low data rates coming from the Campbell Data Loggers
- 9,600 baud being routine - we could make the entire wireless
network comprised by Freewave DRG115 Serial-Port 1 watt 902-928Mhz
radios. And we could use a pair of such radios link the garage/tower
radio site to the main building at tolerable cost - probably less
than construction cost of the cable ditch. We also decided to
go up 10 more feet - to 120 feet on the tower height.
So the first major decision was reached.
1. The tower would
go on the north side of the garage, 120 feet high, giving it 35
feet clearance over the surrounding trees, approximately 30 feet
from the garage building, and 100 feet from the main Research
2. Joe Sanfillipo would come back on his own
and lay out the exact spot the base pad would be built, and where
the three guy wires needed to be emplaced. He would first get
Tim Kratz approval for that exact scheme.
3. Joe would fax the bid for the work and
materials to me, and we would execute the agreement for the tower
to be erected in May. Joe estimated it would take from 2 to 3
weeks after the contract was signed for the tower to go up.
4. The work would include Joe affixing the
915Mhz capable antenna and cable to the tower at the top, and
running it down to the vicinity of the heated room in the garage.
While we were capable of doing that work ourselves, it was desirable
for Joe to do this, since, later, other towers might be erected
for the general research area, and it would be desirable for a
local contractor to become quite familiar with the special requirements
of these low power radio networks and the care and permanency
with which the RF cable lines and antennas had to be installed,
5. The heated room in the garage would be used
for the base radio or radios at the Research Center, using wall,
or grid, power, supplemented by an UPS - Uninteruptable Power
Supply, powering the radios.
THE WIRELESS NETWORK
During an hour-long discussion with all interested
Station personnel present, the Architecture of the entire wireless
network emerged, represented by the following diagram.
1. We decided on the key role of Muski Tower,
whose owners, the Wisconsin Power Company had already indicated
by return letter to me, they were willing to permit an antenna
array to be placed high up on it, and use power in their 'radio
shack' at the base for our low-power drawing, radios. This is
still subject to final approval, but they appeared to be very
cooperative. We avoided asking the owners of the taller tower
at the same general site - a communications company, in which
telephone company equipment is used - for permission. We were
aware that, in general, telephone companies are uncooperative
to requests to put even small, and very small wind-loading radio
antennas on towers they control. Their lack of familiarity with
spread spectrum radios, and their often expressed views about
such no-license (therefore no commercial service cost) radios
as being in 'competition' with them dissuaded us. There is no
competition in the case of utility companies.
At Figure 1 is a digital view up the 200 foot
Wisconsin Power tower.
Tower on Muskie Mountain tower
We would seek to put an omni antenna with 8db
of gain, tuned to 915mhz region high on the tower, and run LMR-400
low loss RF cable down into the Radio Shack, where a Freewave
DRG115 1-watt radio, operating only as a 'Relay' radio would reside.
Freewave DRG115 Radio
Freewave DRG115W Professional
- in Waterproof box
This antenna has a radiation pattern suitable
for being so high on the tower/mountain (small hill). The higher
the gain the antenna the 'flatter' its effective envelope of coverage.
Since the relay radio would have to communicate with 7 or more
radios, from as close as 1 mile, out to as far as 10 miles, the
'envelope' of coverage needed to reach the ground had to have
sufficient depth. Thus our choice.
3. The Relay Radio at Muski Mountain would
be set to communicate with the Freewave radio at the base of the
tower at the Trout Lake Center operating as the 'Master' radio.
Perhaps a 4db Cushcraft omni antenna. Since, even if the Center
radio could reach many points around Trout Lake, it was clear,
because of interfering terrain - low hills - it could not reach
several of the lakes. Thus the Relay Site on Muski Mountain would
be the key radio to reach all sites on the 7 lakes. A single radio
at the relay point, working in 'both directions' cuts the effective
thrupt in half. Thus it can be expected that the thruput from
the Slave radios back to the Master will be no more than 56kbps,
half-duplex. Since the data loggers only operate at 9,600 baud
out their serial ports, this appears to be plenty of capacity.
4. The Freewave radios at the 7 lakes, whether
on rafts, or buoys, or not, would be set to communicate in "Slave
Mode" - a characteristic mode for the Freewave radio. This might
require a directional antenna on each of the rafts, pointing back
to Muski Mountain. Given that the rafts can move, bob up and down
in the wind and small lake wave action, the antennas chosen for
the Slave radios would have to be a compromise between highest
gain, with the narrowest beam path, and a wider and deeper, while
still directional, zone of coverage. Swings of a raft beyond 90
degrees would be beyond the ability of the radios to communicate
at the 1 to 10 mile distances, even without the consideration
of trees up to the water's edges.
5. The Slave Radios, on the lakes, would be
powered by external 12-volt batteries shared with the Data Loggers
at those sites, and the solar panel array which would keep the
batteries sufficiently charged. One benefit of spread spectrum
radios generally is their low power draw. The Freewave radios
are rated at an average of 180 milliamps, 100 to receive and 600
to transmit. The Campbell Data Loggers also operate at 12 volts,
DC, so the shared battery approach is quite feasible and economic.
6. Because the Freewave Radios can be configured
to operate on any of 15 'channels' within the 902-915Mhz range,
it then, with the above configuration of up to 9 radios (Master,
plus Relay, plus 7 Lake Radios) on one hopping pattern, we can
put another pair of radios between the Garage and the Main building,
and interconnect only by RS232 cable, the two radios sitting side
by side in the Garage radio site. They will be set to operate
on different hopping patterns from the Master and Muski Tower/Slave
patterns. In the event that either the thruput, or data response
time from the slave radios and data collectors back through the
relay radio is inadequate, we can, thanks to the design of the
Freewave, configure it as a third network. This would consist
of the Slaves talking to the Muski Tower Radio as a Master, then,
in the radio shack, connecting the RS232 ports on the Master,
to a second radio as a Slave to the Master back at the Garage,
which then connects to a third Master radio talking to a Slave
inside the Center, only 100 feet away. All three sets on different
hopping patterns, thus not interfering with each other, even though
their antennas and the radios are co-located. This of course would
require a second RF cable and antenna, on the Muski Mountain tower.
So we will probably ask Joe Sanfillipo to emplace two cables,
and antennas, rather than one, on the Muski Mountain Tower.
Thus the Trout Lake initial Wireless Network
will look like this:
Proposed Wireless Network
FIELD DATA MANAGEMENT
One issue arose during the discussions, which
has to be thought through - largely by the Trout Lake and Madison
LTER staff. And that is, who can access the data via the wireless,
where does the data reside, and how the interaction between data
storage server at Trout Lake and those operated by the U of W
Data Management staff in Madison.
Currently the Trout Lake staff can dial up
the raft and Weather Station's Data Logger on Sparkling Lake using
a PC with the PC208W software twice a day. The LTER staff in Madison
also, separately, dials, long distance, the cell phone on the
raft, and collects the data in Madison's computers, makes it accessible
with a Web interface from its Oracle data base which all LTER
researchers have access to. The data does not pass through Trout
Lake facility enroute to Madison. The public - 'citizen science'
including students, can only access this data until after Madison
puts it, periodically, on their web site.
Once the Wireless links are up, the data CAN
be delivered, or requested by, Madison, over the T-1 Internet
link to Trout Lake - at no added cost (cell phone and service).
It can also be polled more frequently - even down to every 5 minutes
or so, giving nearly 'real time' data from all the sensors. We
discussed alternate ways that Science students in K-12 schools,
might have access to the data, and/or substantively assist in
the data gathering, storage, analysis, or representation on web
servers accessible to the Public, as well as Science students
The technical capability, policies, security
procedures, to deliver that data from the Data Loggers, first
wirelessly, then via the Ethernetted Internet, has to be decided
before the final 'interface' is installed.
Paul Hanson agreed to work on that matter before
the final design of the network is finally decided.
The wireless links both enable new ways to
gather and distribute the data, and poses new management questions,
THE APPRISE BUOY
After these decisions were made, we spent a
little time examining the sophisticated Buoy by Apprise Technologies,
which was stored in the garage, and discussed with Paul Hanson,
who had to return to Madison, his ideas on linking it by radio.
The Buoy consists of three metal rectangular
tanks that float in the water, connected to each other in a star
formation, each leg being 120 degrees from the other. Inside each
tank are batteries, and on top is a solar collector panel. In
one tank is space and openings for the data collector. A mast
for a weather station is included.
But the main value of the Buoy, resides in
a pair of cylindrical tubes attached to each other, between which
are inserted 3-foot long cylinders which contain 6 sensors each,
or a total of 12. Then the apparatus is lowered into the water
under the Buoy which being loosely tethered to it on the surface,
and a proprietary system of pressure valves for air and water,
keep the device at any selected level in the water beneath the
Buoy, so it can gather data at various depths. Even if the Buoy
bobs around, the sensors remain at a constant level in the lake.
While the Buoy is shipped with a Motorola
radio system, Paul Hanson, realizing the greater power and flexibility
of a pair of Part 15 data radios, procured a set of Aironet Radios
- BR100, which operates in the 2.4Ghz frequency bands, at 100
Milliwatts of power, at 2Mbps of rated speed. To be the base station
on shore. And a PC4500 Aironet, designed to operate in a desktop
computer, into a chassis of his own design, which includes a complete
processor, to put on the Buoy.
This arrangement can be further interconnected
to the router and T-1 link to the Internet in general, but more
particularly to the Center for Limnology at Madison, 250 miles
away. Data can be read real-time from there.
By using this radio system, rather than the
analog Motorola radio, which is mated to the Data Logger low rates
of throughput, it becomes possible to add devices, such as digital
video cameras on, or suspended under, the Buoy, which requiems
substantially higher data rates. (Full motion video can require
384Kbps to 1.1mbps of throughput)
Since the Buoy in this case will operate out
on Trout Lake, there will be no difficulty in communicating from
the vicinity of the shore where the Center is, out across the
lake to its furthest reach with this radio pair, even though the
power is one tenth that of the Freewaves, and at a less tree-penetrating
set of frequencies.
Unassembled Apprise Buoy with
Hanson holding one sensor set.
This system will be launched onto Trout Lake
We spent several hours on Thursday after the
above work, bench testing the operation of the radios I brought
with me, linking the Campbell Scientific software on PCs, to a
CR21X Data Logger.
Working Group at Trout Lake
Tim Meinke at the Trout Lake Center is largely
responsible for set up, operations, and maintenance of the data
loggers. He operated a Center's PC on which was mounted the Campbell
PC208W30 software - which is the key data gathering and analysis
software for all of Campbell's Data Loggers.
As designed by Campbell, the Data Loggers
are connected to the Computer running the software, via a RS232
cable, terminating in the data logger in a DB9 port. However this
is not a completely standard RS232 port. It is connected to an
SC32A Optically Isolated RS232 Interface, which is in turn connected
to the computer, or serial port on a modem for use with a cell
In the simplest configuration, on the table,
or in the field where it is desirable or necessary to get the
data via a physical visit to the location of the data logger,
or to set it up with changed software, an RS232 cable is run between
the computer's DB9 serial port and the SC32A device, and another
RS232 cable is run to the DB9 port on the data logger. The Software
is commanded to 'Connect' upon which the custom software loaded
onto the Data logger responds, showing a connection, and transfers
the initial data.
On the raft on Sparkling Lake, this can be
done, but there is also a Cell Phone on the raft, which is connected
into the Data Logger there, via a modem operating at 9,600 baud.
The Data Logger's program is programmed to
turn on the cell phone for 30 minutes twice a day, to be able
to receive calls from the Trout Lake Station or Madison. A PC
then captures the data at the Center. It is also possible for
the Data Base Managers at the Madison, WI campus, to call the
same way, long distance, and capture the data. This is done as
the primary means by which the Madison campus gathers the data
to put it into the North Temperate Lakes LTER data bases - not
through the T-1 Internet connection with exists between the two
This arrangement of course, works satisfactorily
where there is cell phone service at the field sites where a data
logger is deployed. If, however, there are many sites - such as
the '7 lakes' scenario, 7 different cells phones and contracted
services would be necessary, one for each. This might be tolerable
for one-a-day calls to the rafts and data loggers. However, as
efforts to gather the data every 5 minutes, as was suggested as
an option, was done, the costs would go up substantially. And
of course if any data logger is out of range of the cell service,
no data could be collected. If the same data could be gathered
via the Part 15 no license, therefore free, data radios, and fed
into the Internet at Trout Lake, the costs would be limited, and
data could be gathered on any desirable frequency of schedule.
We substituted a pair of Freewave Data Radios
for the RS232 cables, set down to port speeds of 9,600 baud, and
the Data Collector <-> PC208W software link worked perfectly.
We did this with both the Computer owned by and configured by
the Trout Lake Center, and to/from the laptop Dell Computer I
brought, and had mounted the PC208W3.1 version of the software
(one revision higher than the Center's copy).
Whether or not that continues to work well,
when we increase the distance to miles between the radios, and/or
go through a Relay radio, remains to be seen. But the critical
test of a pair of radios acting as a standard 'serial' cable between
them, was passed using the radios we intend to use in the area.
We did not have such good luck with a second set of radios which
While not completely familiar with their characteristics,
since they were received only the week before, I brought an interesting,
lower cost, set of 1 watt, spread spectrum, Part 15 no-license,
56kbps radios named the World Wireless 900 SS Hopper Data Radio.
What is interesting about these radios, are
that they are much cheaper than the Freewaves, which list at $1,750
each in the weatherproof model. Together with necessary external
antennas, mountings, cabling and power supplies, the Freewave
solution can reach $4,000 for a pair of installed radios. The
990 Hopper radios, including a weatherproof Nemo enclosure, with
sealed leads coming out of the box, power supply, small directional
antennas, cost us $920 the pair. One-fourth the price. But you
get what you pay for in radios.
When we tried to make them link the CR21X Data
Collector and the PC208W software in a PC, they would not work
properly. I spent some time then, and the next day, systematically
altering cables, connectors, and settings in the radios to make
them work. They never did. I suspect, there is a timing problem
somewhere. There are few status lights on the 900 Hopper boards,
they cannot be set up in relay mode, and their configuration choices
are somewhat limited. The problem could also be with the 'optical
interface.' If we get that solved, If these radios prove to have
the same range as the Freewaves - which can only be verified by
comparative field testing we could not do there - they would be
a more economical solution that would scale for many data loggers.
More testing is needed.
GETTING A ROUGH WIRELESS BENCHMARK
The last day, we determined to (1) establish
a rough benchmark for 'how far' in miles and tenths the Freewave
radio would work through the trees of the Trout Lake area and
(2) see what points around the perimeter of Trout Lake we could
expect to get a good connection.
We did not have time to test different sets
of antennas in this 3 hour effort, so we determined to put one
antenna up on the roof of the garage with a vertical 6dB gain
antenna, and drive the second radio around, powered from the 12volt
DC car battery through its cigarette lighter. And to stop periodically
when the green 'link light' indicator on the radio went out, and
test it outside as far as the power line would stretch. The antenna
on the Freewave - a 3-inch rubber duck - has only 2dB of gain,
but I wanted a good bench test at that level first.
Over the next two hours we drove 15 miles around
Trout Lake, observing the reaction of the data radio, both inside
the vehicle when the radio signal would have to pass through the
glass and metal of the car, and outside. We kept exact distances
line of sight with a GPS that was keyed to the original point
and base radio at the garage. As expected, the results were quite
variable. However, we consistently could see that the radios would
lose link after about .8 of a kilometer, or one half a mile, through
solid stands of trees.
Thus our Rough Benchmark is .8 Km for trees
of the type shown in Figure 7, using the lowest gain antennas.
Woods Surrounding Trout Lake
However, since the garage is only about 50
meters from the shoreline of Trout Lake, with only sparse trees
in between, we also found we could satisfactorily connect up at
many points on the perimeter of the lake, even back from the shoreline
through trees until about .5 of a km of trees was reached. As
shown at Figure 8, we had a link at 2.5 miles on the western shore,
4.3 miles on the extreme northern shore at a site called Camp
Fiesta, which had to pass through a pensile about one quarter
mile wide, and its trees, and at 2.72 on the eastern shore, including
behind a quarter mile of trees, where the State Forest Headquarters
has a facility and offices. We also got a good link at the edge
of the research site Bog about 100 meters beyond the lake shoreline.
Coverage from Camp Fiesta
So it is clear, even at the lowest antenna
gain, it will be possible to reach almost any point on Trout Lake
itself from the Garage location (not just from the high antenna
on Muski Mountain, and onto the shore from variable distances.
However, because the land drops away to the east of Trout Lake,
we were not able to get a link at or near the four smaller lakes
two miles east of Trout Lake (3 miles from the garage radio).
But these lakes are directly north and at distances of from 1
to 3.5 miles from Muski Mountain. The antenna mounted there will
clearly be able to reach these lakes, including through from .1
to .4 km of trees.
All these baseline findings however, will improve
as higher gain antennas are used, and high tower mountings of
the antennas are made. And, as is usual for specific Wireless
Installations, the ability to establish reliable links is a function
of a specific engineering site survey of that individual site.
The rough benchmark can be used for general planning and estimating,
but the final plan needs to come from a carefully engineered and
surveyed layout. At the low power levels Part 15 radios work,
and at the high frequencies they must use, only a careful site
survey, with actual radio emissions data can insure that a site
will operate year round, reliably.
And it was also clear from our survey, that
we can use Freewave Radios as relays in places where small hills,
or depths of thick trees blocks our signals from either the Trout
Lake Station, or Muski Mountain sites. In fact, we could even
rely on one of the two radios we planned to link the garage tower
radio, to the Main building, to be in Multi-Point Mode, from where
it could serve many points out on Trout Lake or its periphery.
The main findings we made were that (1) the
1 watt, 902-928Mhz radios can penetrate approximately .8 of a
km through prevailing tree stands in winter at the lowest level
of antenna gain and (2) the Freewave DRG115 Radio has good receiver
sensitivity (3) Freewave DRG115 Radios will be suitable for the
Trout Lake Research Station work, and will scale to at least 7
lake data collection sites.
As soon as the 120 foot tower at Trout Lake
Station, and permission is obtained from Wisconsin Power Company
to install on their Muskie Mountain Tower, we can commence the