Minutes of the 2005 Annual Meeting of the
Communications & Electronics Section of the NSS
Brian Pease, Secretary/Treasurer
July 4, 2005, 1:00 PM
The first C&E Section Field Day got underway as a small group of dedicated members carpooled from the NSS Convention campground site in Huntsville to Limrock Blowing Cave, owned by the Southeast Cave Conservancy. Doug Strait did all of the work to select this cave and allow access to more than the usual size group. He also did two radiolocations, one ~200 ft and a second ~500 ft from the entrance, with stakes in the cave and flagging above. The first was 76 ft deep and the second 87ft deep. Among the people who attended were Doug Strait, Paul Jorgensen, Jansen Cardy, Steve Stokowski, Willie Hunt, Brian Pease, Bart Rowlett, Ray Keeler, plus friends, spouses, and one dog. Bonnie and others took pictures.
Willie Hunt demonstrated his Radiolocation gear, which operates on 325 Hz, a frequency that avoids both 50 and 60 Hz power line harmonics. His transmitter uses a MOSFET H-bridge driving a series-tuned air core loop about 12" in diameter with a crystal-controlled square wave. His receiver, also crystal-controlled, uses a 3-phase synchronous detector with CMOS switches and R-C filters, giving about 5 Hz bandwidth for quick nulling. Larger capacitors can be added to reduce noise. This is really a 6-pole commutating filter. For readouts, Willie uses three zero-center edge-mounted panel meters, which are centered when the signal is absent or nulled out. Offsets due to charge transfer by the CMOS switches are cancelled by summing differential (180 degree phase difference) outputs for each channel. The receiver is not phase-locked, but its frequency is set close enough to drift only about 1 cycle in ~30 seconds, slow enough to not degrade nulling accuracy. Gain control switches set the meter's motion to a reasonable rate. A separate, normal, meter on one channel indicates signal strength when the signal drifts into that channel. It all worked quite well. Willie was able to locate the surface mark over Doug's first Radiolocation with no problem.
Next, We tested my 185 kHz CB transverter voice radios with my ½" dia by 12" long ferrite rod antennas. First we tested several LED lamps for EMI. Ray Cole's 24-LED light was worst (but a very good light despite this!), but even a tiny self-contained Princeton Tec light was pretty bad. All of the switching circuits caused some EMI. Flashes on cameras caused some noise, but an external flash unit was the king of EMI! Ray Cole manned a 185 kHz LSB station just beyond Doug's first Radiolocation, while I walked further in with Jansen carrying a 1 meter square loop. By this time (noon), the weather outside had some clouds with visible lightning, causing the ferrite antennas to become solidly atmospheric noise limited. Despite this, the range was good, perhaps 400 feet using an up-over-down path. We tried different orientations, with the best, as expected, being horizontal with the rods perpendicular to the signal path. Vertical coaxial was second place, with vertical rods third. Ray switched to the 1-meter loop, which brought the signals well up on both ends, along with the noise on his end. At ~500 ft distance I also switched to the 1 meter loop, and we both had S-9 signals on the CBs. We could have gone much further into the cave, but elected to come out.
Willie Hunt and Doug Strait entered the cave with Willie's photo gear and giant strobes to take some big room pictures.
While we were testing 185 kHz gear, Paul Jorgensen set up his Yaesu FT-817 HF rig and homemade 80 meter base-loaded whip, which used a long coil of hookup wire on 1" OD PVC pipe with a ~5ft whip on top. The base had a ~25ft counterpoise of bare copper wire stretched out away from the cave entrance. Bart Rowlett went into the cave and set up his FT-817 with a short mini-outbacker whip with a counterpoise wire. They had good 80 meter voice comms all the way from the entrance to Doug's second Radiolocation point at ~500 ft range.
Lastly, I entered the cave with Ray Cole to do some 80 meter dipole tests. At 500 ft range, I had no trouble talking to Paul with my MFJ dipole horizontal and pointed at him, so we tried some antenna orientation tests. Signals nulled when my dipole was perpendicular to him, and seemed better when I turned it close to vertical. I changed it to an "L" antenna. This gave the strongest signals of all, when the horizontal portion of the "L" was pointed at Paul, weaker when perpendicular, and a shallow null when pointed away from him! Based on this, I had Paul swing his counterpoise to point toward us. His signals rose from S7 to S8! Ray & I moved much further into the cave, to the "breakdown" ~1000 ft from the entrance. At this point we could not hear even a crackle of atmospheric noise, so we obviously were quite deep, or under a conductive layer. I found that I was hearing a little bit of EMI from the IC-703, which was being conducted on the outside of the coax. The L or dipole configuration made no difference. This antenna is direct-driven without a link. Ray's 24 LED lamp made really serious EMI. We were too far away for Paul to hear us, especially given all the atmospheric noise at the entrance. It is possible we could have heard him.
It never did rain, and a good time was had by all.
41 people signed in for 2005 compared with 37 last year. We now have a total of 99 "members" who have signed in within the last 5 years, with 20 known hams.
The luncheon and chat session was 12-2 PM. We did not have the business meeting during this time. We talked about Field Day. We discussed the interference to Cave Radio Communications from the switching regulators in LED lights; propagation paths (up-over-down vs straight through the rock); the increase in conductivity and permittivity with frequency, etc.
At 2 PM, Bart Rowlett called the meeting to order. I read the 2004 minutes, which were accepted, and gave the treasurer' report. There has been no income (except interest) or expenses since the last report. The bill for NSS web space has not showed up yet. The account held $1520.05 as of 5/30/05, compared to $1512.28 last year.
Gary Bush has been doing a great job with the website, which now up to date with every issue of Speleonics through #25.
Paul Jorgensen continues to do a superb job with Speleonics. The web issues look very professional with lots of color.
Bart talked about the Field Day at limrock Blowing Cave, and said that it went well.
Paul Jorgensen said that he was familiar with the Bellingham, WA area, and would coordinate finding a Field Day site at a lava tube cave or mine. Possible projects:
- measurement of the light output and/or light patterns of LED lamps (Doug Strait). This could also be done in a darkened room. One way to do this is with a digital camera and a computer program, but the camera response does not exactly match the human eye.
- Magnetic compass errors in lava tubes. Bart said he has a gyrocompass. This could also be done on the surface of a lava field.
There were a couple of thoughts for section projects:
- The BOG needs a voting machine.
- A digital camera slave flash. Dave Gibson has done one.
Bart called for elections. Skip Withrow ran them. All 4 of last year's officers were nominated unapposed, and re-elected by show of hands. They are:
Bart Rowlett for Chair
Brian Pease for Sec/Treas
Gary Bush for Communications Chair
Paul Jorgensen for Publications Chair
Paul Jorgensen ran his short video/sound clip showing interference to 185 kHz reception by different LED lamps with switching regulators.
Paul showed two portable antennas for the 80 meter ham band. The first was an MFJ 1899T multiband telescoping whip, about 5 ft long, with 50 feet of speaker wire as a counterpoise, which was connected to the shell of the antenna connector, not to the radio, to reduce RF feedback. The antenna could be mounted vertically or horizontally. He had a homemade manual tuner in-line that was not really needed.
The second was a homemade base-tuned telescoping vertical whip about 8 ft long. He used #22 solid insulated wire wound on ½" ID PVC pipe. This antenna is longer than the MFJ, has a larger loading coil, and worked better in tests when the same 50 ft counterpoise was used.
Paul also showed a small 185 kHz ferrite rod antenna that he made by assembling 6 small rods into 3 stacks of 3 in a PVC pipe, then winding on the pipe, tuning, and matching.
Brian gave his paper "Optimizing Circuits Using Computer Simulator", which described using a free Spice circuit simulator program to model and optimize three 3496 Hz beacon circuits. This is much easier than breadboarding actual circuits.
Ray Cole talked about "picaxe" microcontrollers. www.picaxe.com. These are preprogrammed Microchip programmable ICs with built-in basic language and built-in serial port interface. No hardware programmer is required. Some versions have built-in PWM, A/D and D/A, audio tones, etc. It is used by students. There are many websites. Parts and app notes at www.phanderson.com , who also sells on Ebay.
Ray also mentioned Underwater Kinetics, www.uwkinetics.com ,who make UK or UKe dive lights, as a source for rugged, reliable LED lights with real switching regulators.
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