it wont see all of the traffic, it will see enough to earn its keep.

For this report, we tested all of the current portable alerters, flying all of them against the three top panel-mount systems-L3s Skywatch, Garmins TIS and the Avidyne TAS600.

Zaon evolved from SureCheck Aviation, which introduced a line of portable traffic alerters about six years ago. Under the Zaon banner, the company has the premium priced XRX model ($1785 discounted) and the bargain MRX, at $489.

Zaon calls these devices PCAS, for portable collision avoidance systems. The XRX brought new capability to the field in its unique ability to detect not just range, but also azimuth, which it does through what Zaon calls a signal amplitude/phase cancellation antenna mounted in the truncated pyramid atop the receiver. The Zaon models also have their own onboard altimeters, so if the host aircraft transponder fails or doesnt function correctly, the device can still display relative altitudes to tracked aircraft. Its also capable of showing aircraft heading through a built-in electronic compass, which helps with relative bearing, too.

The XRX will detect and display up to three target aircraft, showing range, bearing-with pointer arrows-and relative altitude trends. Threat aircraft can also be displayed graphically via a range ring presentation. All of this data appears on a single, smallish LCD screen, which is the XRXs biggest weakness.

We found it all but impossible to read the screen in bright Florida summer sunshine with sunglasses on. If you want azimuth, the way to go, we think, is to use one of the XRXs remote display options, such as the Garmin GPSmap 396 or the Anywhere Map products from Control Vision. Performance wise, the XRX did well. When it picked up targets, the azimuth was always correct-it shows targets in 45-degree quadrants-and it handled multiple targets in the traffic pattern in a way that made sense. The XRX is sensitive to panel placement; it needs to be as level as possible and it doesnt like to be near obstructions such as the mag compass or a window post. Zaons manuals-which are first rate for the XRX and the MRX-explain this in detail, along with general operating principles.

This is Zaons bargain product, although its performance belies the word “bargain.” The MRX is tiny, measuring 4 by 2 by inches and weighing under 6 ounces with two AA batteries. It will also operate on ships power-12 to 40 volts. A small antenna screws into the left side of the device and there’s a jack for the audio alerts, which are tones only. The MRX is one of the better designed gadgets of any kind that weve ever tested. The bright red LED display is highly visible and logically designed and the single control knob-a round rocker-is easy to use.

Advertised range is up to 5 miles and like the XRX, it shows relative altitude of targets, with trends. It also has a built-in altimeter to fill in for an errant transponder and although it will track multiple targets, it has no azimuth capability. The version we obtained from Gulf Coast Avionics was shipped with a ships power cord and an audio cable with a splitter to tie in a headset.

The MRX will issue advisories for distant traffic and alerts for closer threats, depending on distance and relative altitude. It displays data for what it calculates to be the most immediate threat, but if another target comes into view, it flashes “new,” then gives the new target data.

The MRXs performance was excellent. Like the others, it missed traffic, but generally, it locked on quickly and gave practical if not perfectly accurate range numbers. The audio alerts are logical and easy to interpret. Without question, the MRX was best at tracking traffic approaching from the rear. On some of the passes, only the MRX saw an airplane in our 6 oclock.