For six or eight weeks now, I have been flying with a Zaon MRX air traffic detector. I've been borrowing it from Joe Greblo, on condition that I report my experiences with it. Here's my half of the deal.
The short version:
The Zaon MRX is a small gray box, about the size of a deck of playing cards, with a little antenna and powered by two AA batteries. It detects the transponder signals sent by powered airplanes, and displays distance and relative altitude (but not direction). It will beep an alarm signal when another airplane gets close. My results with it have been mixed. It reports some non-threatening aircraft parked at Camp 9 and elsewhere, and I haven't yet gotten it to report all genuine collision risks soon enough to be useful. However, it has indicated some inbound air traffic well before I would have seen it unaided. The device shows enough promise that I've ordered one of my own (about $500 from Windsports), and will continue to experiment with its settings and configuration.
The long version:
The device:
Zaon is a small business, founded by Zane Hovey (the technical guy) and Jason Clemens (the business guy). They make two products, the XRX and the MRX, both of which are Portable Collision Avoidance Systems (PCAS). The simpler MRX has a list price of $549 (cheaper from Windsports) and has a single antenna; the more sophisticated XRX has a list price of $1795 and has an antenna array and more elaborate display. Both devices receive and decode the transponder signals that are transmitted by nearly all other aircraft in the Los Angeles area. Those signals contain the pressure-altitude of the transmitting aircraft, and by comparing this to the PCAS's own internal altimeter, it can compute the relative altitude of the other aircraft. Based on signal strength, the PCAS devices can also estimate a rough distance. The XRX has an antenna array so it can determine the direction of the other aircraft; with a single antenna, the MRX cannot. The MRX displays relative altitude and distance of the greatest threat on its LED display, while the XRX has a more elaborate display and can be connected to an external GPS. Both are intended to sit on the glare shield of a private plane, and while the XRX would be awkward on a hang glider, the MRX is entirely practical.
I was generally impressed with the engineering of the MRX. The display is very simple and easy to understand. The five-way switch isn't intuitive, but there are aren't many options and they only need to be configured once. While the device is a little delicate for hang glider use, those who treat their flight instruments with reasonable care will have no trouble with it. For the geeks in the audience, the electronics inside are pretty straightforward. It contains a 1090 MHz receiver, a solid-state altimeter, a magnetic sound transducer for the alarm, power supply circuitry, and a PIC 16F877 microcontroller to do the thinking.
Running on two AA alkaline batteries, I found that the MRX runs for several flights, perhaps six flight hours though I haven't kept track properly. It has an audible low-battery chirp, and it keeps working for about a half hour after this starts. For routine use, I plan to use rechargeable batteries in the same way that I do with my radio and GPS.
The manual is detailed and well written, and it is available online here:
http://www.zaon.aero/component/option,c ... Itemid,33/.
In flight:
The MRX sounds an alarm when a threat gets too close. The threshold can be set; my experimentation was primarily at 0.8 nautical miles. When thermalling or flying slowly, I hear the alarm. But the alarm can be drowned out on a faster glide by wind noise, vario noise, and radio chatter. I found it essential to mount the MRX right next to my vario so when looking at one, I would automatically see the other. It turns out that I look at my vario often enough in flight that I see most of what the MRX says. Unfortunately, the LED display is impossible to read in full sunlight. A simple little sun shield would probably improve the situation, but for the moment, I have to shade it with my hand or wait for the shady half of the turn while themalling.
Airspace in most places aside from Kagel is pretty quiet. At Crestline or Garlock or Hurricane or Blackhawk, the MRX's display is virtually always blank, showing just a couple dashes so one can tell that it's awake. Not so at Kagel. Perhaps 70% of the time, it reports an active transponder somewhere within its four mile range. Often it's at that maximum range, 1300 feet below, and I ignore it (the majority of my flight time is spent between the 2200 and Lances, at launch level plus or minus 500 feet). I've been unable to identify the location of these transponders. There is also a significant amount of transponder activity from Camp 9, when they evidently have a helicopter powered up on the pad. I don't mind knowing this, because it is a warning of potential air traffic.
Not surprisingly, my experience with genuine collision hazards is a little sparse, though it's what we care about most. Sometimes the MRX works perfectly, pointing out the air traffic before I find it visually. It has been particularly good about low-altitude helicopters that can get lost visually against a mottled sagebrush background. Inbound aircraft arrive very fast, and I have not yet figured out how to get the MRX to dependably give enough warning to be useful. Conversely, I sometimes see an inbound airplane that never appears on the MRX display. I can't believe these don't have active transponders, so perhaps the MRX senses a sufficient altitude separation that it doesn't perceive a threat.
Current conclusions:
I don't yet see the MRX as the magic solution to eliminate our risk from midair collisions. On the other hand, I still think there's reasonable hope that it will help to reduce that risk. A midair collision would probably be fatal to the glider pilot involved, perhaps also to those aboard the powered plane, and perhaps even to the sports of hang gliding and paragliding nationwide (imagine a rule change that prohibits us from flying in Class E airspace). I don't think such a collision has ever occurred, but one could reasonably predict that the first would be at our site. Hence this problem must be solved, and SHGA pilots are the appropriate ones to solve it. I have ordered an MRX of my own and will continue to experiment and report my results. If you would like further information, I would be happy to discuss the topic, and I'm sure Jim Thompson (another MRX owner) and Joe Greblo would too. If you would like to try one out, I'm willing to loan mine when I get it, and you could probably arrange to borrow one from Joe as well.
