Diary Entry # 9

June 11-15, 2000

INITIAL SUCCESS IN EL YUNQUE

 

The first priority, set by Jess Zimmerman, the Principal Investigator in the El Yunque rain forest of Puerto Rico, has been to link the three Weather Station Data Loggers, each of which perched atop 120 foot towers that rise above the rain forest canopy, to the El Verde Research Station. From which point the data could be both analyzed and captured by the computers accessible to researchers right at the Field Station, and then linked, eventually, real-time back to the Ecological Center at the University of Puerto Rico, 15 miles away, and through its net connections to distant researchers over the Internet.

 

Because of the dense vegetation, in spite of relatively short data radio distances - from 2 to 3.5 miles, we decided to use radios which operated at the highest FCC allowed power - 1 watt for spread spectrum, no license (Part 15 FCC Rules), and at the lowest allowed no-licence frequencies - 902-925Mhz. The lower the frequencies the more penetration of the RF signal through obstacles.

But the three installed Data Loggers at Bisley, El Verde, and Pico del Este are a mix of CR10X and CR21X Campbell Scientific models, and only require 9,600 baud data rates. They are equipped with slightly modified RS232 9 pin female ports (only 5 votes on the pin outs, rather than 12) on the logger itself, to which we would have to connect the radios. (As distinct from connecting to the memory module which is customarily carried back to the laboratory from the Data Logger location in the field, and then connected to a computer's RS232 port running the PCW230 software)

We decided to base the backbone of the El Yunque LTER wireless links on the Freewave DRG115R and W Series radios. For these 'W' series radios not only operate at the full 1 watt of power at the radio (with up to 4 Watts EIRP allowed at the antenna) and within the 902-928Mhz frequency range, but also have advanced 'repeater' features, which we figured we may well need if we cannot gain sufficient line of sight conditions between the towers and the planned repeater sites. The Freewaves feature standard 9 pin female RS232 I/O ports which can be set from 1,200 to 115,000 bps from the configuration menus. The 'W' radio is designed for outdoor use. They are waterproof. The 'R' model looks the same, but are not waterproof.

 

While the Freewave radios in these 'W' and 'R' configurations can be considered 'too much radio' - 115kbps radio for the 9,600 baud need - and are pricier than others - from $1,350 (R) to $1,750 (W) list price, they have a top reputation, are extremely reliable, have excellent radio 'receiver' characteristics - needed in thick vegetation - and are very configurable. We think they are ideal for 'backbone' links to important data logger sites - such as full, many-multi-sensor weather stations, as the three in El Yunque are.

In fact the latest Freewave models, have three advanced features which we would like to use.

1. The radios can be set up in a new 'network ID' mode (not TCP/IP) rather than every radio having to be entered, by radio ID, into Call Books. In the Call Book method, every radio is instructed what other radios - by ID - they must communicate with. Then, if one radio has to be replaced for reasons of failure, not only must its Call Book be updated, but every radio it is supposed to talk with has to be changed in their Call Books. When all radios are easily accessible, that is no big problem. But when some of the radios in the net are put in inaccessible places - such as on high towers in the case of the Rain Forest, or out on water bodies, it can be a major effort to visit, and reconfigure them all, on the spot.

When the Network ID system is used, the Call Books are NOT used, so radios can be replaced, without the need to reconfigure the other, often remote, radios, by physically carrying a laptop and RS232 cable to the location of the radio - close to the data logger.

2. A new mode called 'Repeater/Slave' has been introduced, permitting one radio to both become a 'repeater' station, AND send and receive data out its RS232 port. In the El Verde Tower case, we will use this feature, so that the radio we must mount high on the tower closest to El Verde Research Station buildings, can be attached to the Data Logger on the Tower which captures Weather data, but it can also 'relay' or act as a repeater from the more distance radios, down to a Master Radio inside the El Verde Station - the terminating point for all data collection efforts, by wireless links.

3. Freewave also integrated the ability to do remote 'diagnostics' wirelessly with PC software, which will help as we study the performance and reliability of the radios in this difficult environment.

Radio Network Architecture

The following schematic shows our intended architecture for the Freewave network.

Since there is no direct Line of Sight between the Bisley or Pico del Este Tower locations back to the El Verde Tower which looms right over, and is within 100 meters of, the El Verde Research Station buildings, but all three Towers can 'see' the highest peak in Puerto Rico, El Yunque, we decided to make the El Yunque peak a radio Relay Point for all three Tower radios.

Then, since El Verde Station itself is below the canopy level, and cannot 'see', even from its roof, Pico El Yunque, then we can, using the 'Repeater/Slave' mode of the Freewaves, make the El Verde Tower radio both a data collector from the Data Logger next to it, but also a Repeater Link between the Master Radio inside El Verde Station, just 100 meters away and down 120 meters in elevation, and the El Yunque Repeater Radio.

New Team Member

Because, over the long term, we want the LTER staff to be capable of designing, installing, maintaining, and troubleshooting wireless networks supporting their field data collection needs, we recruited, on the recommendation of Jess Zimmerman, one of the Techs who maintains the Internet systems at the University of Puerto Rico Ecological Institute back in San Juan - the base of operations for the LTER and El Verde Research Station. He is Andrew McFadden. So he assisted us the three days Mike Willett and myself were at the Research Station. And will be able to assist me when I travel there without Mike Willett, and as he learns more about the wireless arts, can begin to undertake installation tasks on his own, from where he lives and works in Puerto Rico.

This is part of the important 'wireless technology transfer' phase I think is important for every one of the LTERs who hope to adopt wireless data collection on any scale. There are simply too few wireless knowledgeable technicians yet at Universities that are the base institutions supporting LTER activities. And few are out there for hire - since corporate America is snapping up all the RF engineers and technicians they can as wireless is becoming more and more a main stream Internet connection technology.

Preparation

The first task was to configure a pair of Freewave radios, one as 'Master' to place inside the computer room in the El Verde Station, close to a PC that can run the data logger software. Where the radio can be connected by a short 9 pin RS232 serial cable to the computer. Then to try a small 0-dB gain omni antenna on a short piece of RF cable to move the antenna close to the windows on the wall nearest the El Verde Tower - which, being only 100 meters or so, through thick vegetation, to the north - ought to be able to get a satisfactory link to the Slave-Repeater Freewave radio on the Tower.

The pictures below is of the Master radio (next to a large HP Printer)

And the small omni antenna leaning against the windowsill behind a fan and birds nest.

The Slave Repeater configured radio, a DRG115W, had to have its 10 line, weather proof cable split off to feed both an RS232 connector and and draw its power from a separate 12 volt (Marine West Deep Gel Cell 31) battery, which would be constantly recharged via a 45watt Solar Panel, also to be installed on the tower. We had some discussion about whether to use a 6db Omni on the tower, or a 10 db Yagi - pointed toward the El Yunque peak where our relay radio would be - and depend on its 'back wave' (rearward from the Yagi, but at much less radiated power than the concentrated forward RF envelope) to be strong enough maintain a link with our inside small omni connected to the Master Freewave - since the two radio antennas would be less than 100 meters from each other. Mike argued we should, if it would work, use the lower db Omni on the tower, so it could serve data loggers that might be deployed close to the El Verde Station. I was doubtful, but agreed for this installation to try it, and see if the signal was strong enough linking to an Omni, which we would have to use (so that the other two or three outlying radios could link to it at greater distances using Yagis.)

The photographs below shows Mike Willett on the lower steps of the El Verde Tower. And the tower itself, 120 feet high to clear the canopy.

Thus our wireless rig on the tower, separate from the battery powered CR21X Data Logger system with its own battery, would consist of:

Freewave DRG115W Radio configured as Slave Repeater 3dB 915mhz Omni 915mhz

12 Volt, 31 Amp Hour Marine West Gel Cell Battery

45 Watt,18 Amp Hour Sieman SM-46 (13 x 43 inch) Solar Panel

Plastic box for battery, and, optionally, the radio.

LMR 400 (low loss) RF Cable and connectors

Mounting brackets to affix to the tower

Later, once good radio links were established we would add the RS232 cable from the Radio, and a required (from Campbell Scientific) SC932 9 pin to 25 pin DCE Interface to link the Standard RS232 Port of the Freewave to the nonstandard RS232 port on the data logger. At which time, so long as the Computer Room Windows 95/98 machine was mounted with Campbell's PC208W Software, there would be a direct link between the Data Logger on El Verde Tower and the Data Software in the Center.

 

CR21X <-> Slave/Repeater <--wireless--> Master <--> PC/PC208 Software

Initial Installation

 

Mike Willett and Andrew McFadden climbed the El Verde Tower, and over the next half day, mounted the radio system.

A unanticipated problem was encountered, however, when we discovered that the tubular opening in the bottom of the plastic case enclosing the CR21X Data Logger on the tower, carrying cables to each sensor, was both too narrow (diameter) and too jammed with cables, to permit the standard 9 Pin RS232 connector, with its flared brass plates, to fit through the opening. It was exacerbated by an even narrower 'collar' used to leave the smallest opening possible in the weatherproof plastic box, on the bottom side, so than water cannot get into the box and short out the data logger.

Several attempts to reduce the size of the connectors without destroying the integrity of the 9 pin configuration failed. And it was realized we would, wherever this was the type case being used, be obliged to take a portable soldering iron to the tower locations, with stripped cables, feed the cable through the opening, then solder the wires into the RS232 connectors while inside the box, and then make the connection to the I/O port of the data logger. A very inelegant solution, with its own risks of creating unreliable connections.

We left that task to later, since the software was not mounted on the PC in the Computer Room by the LTER staff, so an immediate connection would not be needed.

Once the Tower system was mounted, we had, as expected, a solid link between the Master Freewave inside the El Verde Computer Room through the walls, to the radio on the Tower. The first link works. We left it up and powered.

Top of El Yunque Peak Test

We encountered another major problem as we prepared to go to Puerto Rico. Efforts to contact Castle Communications, which has a major lease from the US Forest Service permitting it to operate private antenna towers and facilities on the top of El Yunque, was unsuccessful. In fact we were prepared to pay Castle Communications to mount one of our (quite standard) antennas on one of their towers on top of the peak, so when we got there, we would connect up our Relay FreeWave Radio, running the RF cable inside their fully-powered facility and use 110V wall outlet to run our relay radio. We knew there would be some 'rental' monthly fee for the use of their tower. But we did not know what that fee might be, which eventually would have to be paid by the LTER project.

Not only was Castle Communications - the key persons - almost impossible to contact, once contacted, they claimed that any plan of ours would have to undergo an Engineering Review, would take a long time (and lots of paper work). Arguing that this was such a small, low power radio standard device, with a very small antenna (maybe 3 feet), unlike almost all of their heavy duty, large hooded antennas, carrying large wattages for a variety of customers didn't help. The picture below shows one antenna array managed by Castle Communications, on El Yunque.

So I decided, since the LTER is a Federally funded, University, project (not a private business), and the top of the mountain belongs to the Federal government, managed by the US Forest Service, location, that I would attempt to make all arrangements through the Forest Service, using their mountain-top facilities, or ground outside Castle Communications leased space. So I put in a call to Fred Scantina, the collaborative-LTER research project manager, who is making arrangements for doing this entirely on Forest Service land on top of El Yunque, on a later visit. (now planned for the last week in July)

But we still needed to know how the radios would work down the mountain to El Verde, in any case. So Mike Willett and Andrew McFadden, carrying a third Freewave radio, set up as a 'Repeater' station in a way that its Green 'Connection' light would operate and tell them a connection had been made, but identified in the Call Book to link to the El Verde Tower Radio, an Omni and a Yagi antenna, connectors, and a small 12 volt battery, and one of two Motorola handheld voice radios, drove up the mountain as far as they could go without keys to the top of mountain access road gate.

There is a one mile long public hiking trail that takes off from the gate, and goes to the top of El Yunque. They hiked up and attempted to call me on the Motorola. I could hear them all right, but the RF environment is so dense on top of El Yunque, and so many distant voice radios were in use, they could not hear me answering. But I knew they were there.

They first attempted to get a link light with their hand held Omni antenna. That failed. The two weak db-gain antennas just could not connect with each other down that 2 mile distance. So they then mounted the 10 db directional Yagi antenna, and got a link. But it was not a very solid link, by the evidence of the fluttering of the green link light (which an experienced installer can interpret). They even climbed to the roof of the Castle Communications building, and its large tower, to do a hand held test. But they reported that, because of the intense RF in the vicinity, that it got them a worse link than on the ground level.

This somewhat confirmed my belief that we would need directional, 10dB gain antennas at all downhill sites on the three towers, including El Verde, pointing to either an Omni on top of the mountain, or even requiring a 'sectorized' directional antenna up there, which would give good gain in several directions (sectors). A very specialized antenna array.

But we learned what we needed to. Even with some masking of trees on the slopes of El Yunque, we could establish a link with Freewave 1 watt radios to the Tower, and Computer Room of El Verde Research Station. Now we would have to, working with the Forest Service and not Castle Communications, find a suitable place to mount our Relay Radio on El Yunque And face the possibility we would be unable to 'see' all three sites (Pico del Este, Bisley, El Verde - and even El Toro peak to the southwest where the Coqui-sound radios would have to be put) without further relay radios.

Between the dense vegetation, the few 'peaks' that dominated the forest, and those very much in demand by many radio operators, the thick RF environment, and plain old bureaucracy, just getting one relay radio to work - a $1,500 investment - on top of the most desirable peak, is a big challenge. No big surprise to me from the first day I saw, as we drove up to, Peak El Yunque, the large and numerous commercial, government, radio installations on the small peak. But a lesson all other LTERs need to heed. Everybody wants to use the same high peaks.

Surprise Success on the Jungle Floor

While work was being done on the Weather Tower radio links, I started to work with Dr. Jill Thompson, whose main research project involves monitoring the 44 light-sensor array in a plot of rain forest floor north east of the El Verde Research Station on the far side of Sonodora Creek. Four CR10X Data Loggers are deployed in four locations inside what is referred to as the 'Big Grid' 500 meter research plot. Then each Data Logger, in turn, is connected, by wires to 11 very small light sensors which record the amount of light hitting that spot on the forest floor.

Besides attempting to link the four data loggers back to the El Verde Station, wirelessly, in the long run we will attempt to model the connecting up of the sets of light sensors to the data logger wirelessly also, with tiny broadcast radios. This is because Jill experiences many interruptions in her data collection, as tree branches fall, breaking the wires, jungle rats chew on the wire installation, and bigger beasts trip over, and break the wires. That is a later challenge.

The first task on this visit was to test both more costly, and powerful Freewave radios, and very small World Wireless Microhopper radios, to see if they will penetrate the jungle floor laterally, out to Jill's research sites.

So, having set up a FreeWave radio, with small rubber-duck antenna, and a separate Microhopper radio with small whip antenna inside and at a window looking in the direction of the Research Plot, then equipping myself with a portable battery, a corresponding pair of radios, a Yagi antenna, and a laptop computer with Microhopper software installed, we set out through the forest.

I had to carry the laptop, because, unlike the Freewaves, which have status lights on the front, and thus give you an indication of a good link, the Microhoppers, to conserve power when attached to a battery, have no such lights. So the only way one can insure there is a link, is by running the software, that reports the quality of any detected link by the radio at the laptop. With mud boots, plenty of mosquito repellents, and a light rain jacket, we set out.

A close up of an uncased Microhopper. Note the fingernail.

To give some idea of the relative size of the Microhopper, the pictures below shows two Microhoppers, a 12 volt battery which can drive one, and in the foreground a single light sensor of the type Jill deploys. All are sitting on the metal case of a Canadian Wi-Lan 915mhz T-1 Frequency Hopper radio.

Our map calculations showed that the nearest data logger would be at least 600 meters from the El Verde building, through solid forest. With unknown effects from low ridges in the uneven terrain.

We proceeded through the trails and across the suspension bridge during a light rain, over the Sonadora. The bridge is quite high - 15 or so feet over the creek level, for rains cause rushing floods down the narrow creek that rise quite high.

About halfway to the closest data logger site, we stopped and tested both radios through the 300 or so meters of forest. As expected both worked quite well at that distance. An important finding, since, if we would be unable to connect all the way from the furthest, 600 meter point, we could consider putting a relay radio in this vicinity.

We continued on to the data logger location, but not before I stopped to admire a jungle phenomenon - a tree exuding large quantities of a white sap, the Taitano Indians were reported to burn as a kind of insect repellent.

When we got to the first data logger, having gone down some slopes as well as up - while Jill experienced in this part of the forest felt we were not masked by terrain from El Verde Station (of course we could see nothing but forest out to about 50 meters) - we set up the radio tests.

The picture below shows Dr. Jill Thompson at her first site. The box on the ground contains the CR10X data logger, with a post on top of which is one of the light sensors. The yellow tape denotes the path of the wires that extend, with light sensors every 5 meters to the limit of 11 sensors, or about 55 meters.

The next picture shows me, a bit bedraggled from the wet, rainy walk holding the Microhopper up, connected to the laptop. To my great delight, the small 100 milliwatt Microhopper radio connected with its mate back at the Center, using only the small whip antenna!

While not very clear in jpeg, the following is the graphical report on the quality of the link on the laptop CRT.

We ran out of time (light) before testing the radios from further data loggers, from 50 to 100 meters further. But this test at logger #1 told me that if they could not reach all the way back, the Microhopper at Logger #1 site can be used to relay the signal.

For one of the powerful characteristics of the 19.2, 915mhz, 100 milliwatt Microhoppers - which in custom waterproof cases which I have ordered from World Wireless would cost $500 or less - is that any one of them can be used as a point to point, point to mult-point, or relay (up to 7 hops) radio!

With the discovery that we can reach the forested sites that far through medium-density forest, I immediately saw that we can, at last, deploy at affordable 'scale' data radios that can serve many deployed data loggers, in many LTER sites.

My search for the smallest radios in the world has not been in vain.

Planning for El Toro Peak

We were unable to meet with Victor Cuevas of the Forest Service, the general Biologist who works with recording the Coqui sounds of the Richmondi subspecies on El Toro. But we made arrangements for Andrew McFadden to meet with him soon, to get far more details on the El Toro site that we would need before embarking on that task.

I, in turn, scouted out the entry point for the hike up El Toro. And found it. The pictures below show the peak (I believe. I was alone when I took it), the entry sign, and the trail beginning.

Conclusion

With the above activities, we departed Puerto Rico, to prepare for later trip to make the permanent installation on El Yunque Peak, and as soon as back ordered solar panels arrive, install slave radios on Pico del Este and Bisley Towers, and plan and site survey further on El Toro, to hook up the elusive Coqui, which I heard, but never saw, in the jungle.

 

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