---------------------------------------------------------------------- Mammoth Cave APRS Test Plan [ revb ] 25 Jan 2013 ---------------------------------------------------------------------- WB4APR Updated 25 Jan to add Higher power digi test Updated 11 Jan to add Cleveland Ave plan. Date: 2,3 March 2013 (saturday and sunday of Cave City Hamfest) (also volunteer weekend in the Mammoth Cave Park). Time: Maybe a Saturday AM and PM and follow-up Sunday test? A formal Test Proposal has been submitted. It is not for public release since it might contain some detail not for public release? (I'm new at this and don't want to mess up). This file is my attempt at collecting some of the ideas... I suspect we will need 2 days since some of us will be coming from great distances. Probably plan on doing the initial tests on Saturday morning and then use saturday afternoon to condense what we have learned and then re-group Saturday night for followup tests on Sunday morning. WEEKEND OVERVIEW: This is volunteer weekend in the cave and so there will be lots of activity in the non-public areas of the cave. Since we will probably need to be continually going back and forth along our test route, I have also volunteered us to help carry out any trash being rounded up by other cave volunteers that weekend working in the same passages. This gives us maximum working experience with our network while also being useful to the overall weekend goals without being a burden on our hosts. GENERAL TEST AREA: See the Cleveland Ave map link on the web page. The Cleveland Ave area of the cave is lighted and is a route for some of this volunteer activity. It is about 4000' long and will make a good initial test area. We propose two VHF Teams entering from opposite ends. One enters at the Carmichael entrance and the other from the elevator. They test and deploy digipeaters as they proceed until they meet. As many as 7 digis each may be required, but anywhere along the completed 14 link chain, the data is never more than 7 hops from an end. VERTICAL LINKs: We have tested a 5 Watt VHF link from a car in the hotel parking lot to an HT in the "Rotunda" room in the cave, and a signal was barely detected. We are assuming that if we add 16 dB more link gain (better antennas and 50W, and better location) we can penetrate maybe 150' of rock with a working VHF link. This would work here but most other parts of the cave are much deeper and will not work this way. Fortunately, right at the Carmichael Entrance we should be able to make a link with about 100' of rock and at the elevator end we hope that passive RF coupling into the 240' power cable drops there will work for another vertical link. If time permits, we will also see if coupling into an abandoned 4" water pipe might also link a topside digi to one in the cave near the snowball room. HF Test1: The HF test team will enter from Carmichael and proceed to beneath the Bike Trail area. Teams above and below ground will establish HF comms there and then test all bands and all modes. Hopefully building up to a viable packet link (probably on 10 meters where 1200 baud packet is legal. Maybe using FM?) Rock thickness there is about 240'. HF Test2: If we have another team, then they do not fuss with all mode testing, but simply move along topside and in the cave to maintain overall contact with net control or whatever for voice coordination Initial VHF/UHF LINK Test Procedure: 2 VHF and 2 UHF continuous 5W beacons are placed at the starting location (Either the entrance or the location of a vertical link) one each in the center of the opening, and the other near the side.. Several cave hikers each with his own HT proceeds into cave walking abreast assessing signal strength to determine where in the passage the signals are strongest, where they fade, how signals may bend with the passage, and which band is best. When max range is found, that leg is documented and a digipeater is placed at the best location. Then the beacons are moved to this new location and the test repeated farther into the cave. We assume that VHF will work best in these 20-40' wide Mammoth Cave passaves but we also are gathering UHF experience too. Once both teams meet in the middle, then the full length of Cleveland Ave should be temporarily outfitted with digipeaters. At this point we can volunteer to make a few trips hauling out debris for the other volunteer teams while assessing our connectivity as we go. VHF 50W test: Given that several of our digis are D700/710 radios we should then re-do the placement starting at the ends with these digipeaters at 50 watts instead of 5. Then document how much better (if any) this might extend some of the hops. Although this increases link power by a factor of 10, it may not extend the range very much since most digi placement is due to major bends in the passages and not just power loss. Although this might appear to give unbalanced links to HT's, it does not because the digi-to-digi link is what needs the maximum range (50W) and any HT anywhere between them is always within half the distance and usually a straight line shot to one or the other digi. This is because in a cave-link system, range is not limited by actual distance but by turns in passages. UN-WIRED VHF Test Procedure: Since Cleveland Ave is fully wired for power and phone, we do not know how much of this metalic infrastrucutre is enhancing our ability to communicate. So we will then proceed out Carmichael and into the adjacent Violet City entrance which is unlighted. We repeat the test as far as we can go with 7 or even 14 digipeaters as time permits. This test will give us experience in an unwired passage. SMALL PASSAGE TESTING: The above test is repeated in a small passage area. Charles Fox of the CRF suggests Emilie's Puzzle near the elevator. Again VHF and UHF are tested. Theoretically VHF should be good down to a 3' wide passage if the theoretical "waveguide" effect applies (but rock is not conductive and this effect might be non existant. SInce only the WIDTH matters for a vertical held antenna, a good long NARROW but still walking passage would do nicely. In this case, rotating to horizontal antennas should restore some range. Our volunteers are not generally cavers, so for small crawling passage testing, we would prefer to find a variety of such squeegee passages 18"? that happen to be realitvely easy to access from BOTH ends via orthogonal larger passages so we can do the test through the passage but without crawling. This method is invalid of course if there is a second parallel large passage in the same direction where RF would leak around the test passage. BAT BAR TEST 3: Does RF penetrate the Bat bars? DIGIPEATER PLACEMENT PROCEDURE: Once the BAND and best location has been determined in a cave cross secion, then the first APRS beacon will be placed there and activated on a 12 second rate. The team will proceed inward until 10% beacons are lost. Then back up for a solid link. There, A digipeater is placed (with 2 minute beacon). This process is repeated. The second digi will get a 3 minute rate. The third will get a 5 minute rate. 4th, 5th 6th and 7th will all get 5 minute rates. All radios will probably use an outgoing path of HOP7-7,WIDE2-2. See the web page for how this transitions topside. When 4 hops are demonstrated reliably, then the initial digi with the 12 second beacon will be reset to a 30 minute rate. Digipeaters will ONLY be activated when placed. Range Extension.Test: Beyond the 7th digipeater, if packets are all reliable, then the Entrance and first digi will be reset to a 2 minute rate. Each new additional digipeater will get a 10 minute rate. After a total of 14 digipeaters and 2 end stations, the maximum range will be assessed. LATERAL TEST: This test will pick a useful side passage to demonstrate the capablity for extending the main link outward. Again, this is just a draft set of concepts. Bob, WB4APR