During an idle moment I downloaded the PlanePlottter software published by COAA and hooked it up to my WinRadio G305e receiver. Much to my suprise I’m getting fairly decent results with an antenna just sitting inside without a proper ground plane, not a great deal of activity because the Hobart (Tasmania) airport is hardly buzzing with activity but I have managed to pick up one signal close to 200KM away. When the weather fines up a bit I’ll try a proper antenna installation and see how it goes, at the moment I noticed I’m getting quite a few CRC errors and coverage is fairly directional as I’d expect with its current location.
So far the best ACARS settings for the WinRadio seem to be 131.550MHz (Australian / International ACARS frequency) in AM mode with the IF bandwidth set to 14KHz, smaller IF bandwidths seemed to get less reliable. I’ve got the RF section set for fast AGC with the preamp enabled but disabled the SAGC feature and any form of audio filtering. Setting the audio level also seems fairly critical for best performance, using the signal view in PlanePlotter I have it set so the noise floor is not a great deal larger than the graticules on the chart. Here’s an example message received earlier that contains GPS information:
—[2009-09-07 08:33:24]—
{SYN}{SYN}{SOH}
M {mode}
.VH-JQG {rego}
{NAK} {ack}
3L {unknown message type}
4 {block}
{STX}
M55A {seq}
JQ0711 {flt}
S 41.272/E146.515 /UTC 0834
{ETX}
PlanePlotter has displayed all positions so far without altitude, course or speed information. I’m not too sure what that is about, I thought especially the altitude would have been critical information. Anyway I’ll get it setup a bit better and keep my eye on it, the PlanePlotter software also supports Mode-S receivers which I haven’t looked into but maybe the standard ACARS transmissions don’t include the additional information.