Communications & Electronics Session Minutes
2018 NSS Convention
Monday, july 30, 2018
Brian Pease, Sec/Treas
The C&E Session started at 1:30PM in room 124 of the Capitol High School. The small non-air conditioned room was overcrowded with as many as 42 cavers, some standing.
Sam Rowe gave the history of the Special Event Ham Radio station at the NSS Convention over the past 5 years and asked for operators to help during the week.
John Lyles gave is talk on testing HF radios in fairly shallow New Mexico caves. He used the Dell Axim X50 Windows Mobile PDA with PocketDigi software running PSK31to generate audio. He purchased a very small 30 meter (10MHz) crystal-controlled SSB transceiver from the transverters-store (Ukranian) on Ebay. He said that a tuned dipole or loop make an efficient antenna on 30m. He used an MFJ helical mobile dipole with a balun, but still needed a tuner and SWR meter in the cave. He has not done the actual testing yet.
I gave my talk on Experiments with custom WSQcave Radio text mode software. The software operates on 5 kHz I demonstrated using an audio link between computers to get automated responses to requests for s/n, location, etc. The benefit is that one of the stations can be unmaned but still receive a message or transmit a previously recorded message on request. Also, the link can be tested from either end at any time.
Paul Jorgenson gave a talk on attempts to find where the air goes in the commercial Grand Canyon Caverns. He started by bringing a temperature/humidity meter into the cave, but soon changed to data loggers. He used UNI-T loggers which look like USB data drives with temp/humidity/atmospheric pressure in the fancy version. He cautioned that these will only work up to 90% humidity, ie desert caves! They can take 60,000 readings with good battery life. Used for 4 months at 3 min intervals. They can be calibrated, so all set to read the same. He was able to show that when air pressure went up, the humidity went down. This is an ongoing project.
Ian Drummond, VE6IKD, Described his SOTA (Summits On The Air) efforts. His equipment includes a 5W FT817 with a 45W booster amp run at ~30W, and a 20/17/15m dipole with clips to change bands, set up as an inverted-V, with a 20 ft pole guyed 2/3 of the way up. The radio is directly under the antenna with no balun used. He uses SSB voice mostly on 20m. He uses a 5 AH lithium battery. He found that a high stability oscillator was needed in the radio due to the temperature extremes.
Craig Cantello talked about the DARPA SUB-T Challenge to create an autonomous robot map to underground tunnels, bunkers, and caves in challenging conditions. The test tunnel will be featureless, the bunker may contain ferrite material and be collapsing during the visit, the cave might be smoke filled, and there may be water hazards, low passages, obstacles, etc. There will be radio interference. Distance may be 1km. The data has to come out, but the robots don't have to. Most of the non-military vender teams have already dropped out.
John Lyles showed his attempt to build a wind generator to use at the entrance of a cave he has purchased. It failed due to insufficent wind energy. He also tried a quality CO2 detector in the cave, which pegged at it's 500 PPM limit.
The session ended at 5PM when the school closed.