Category: Amateur Radio

I spent some hours today trying to receive a balloon travelling nearby on 2m 1200Bd AFSK.

At the end of the day, I note that the balloon was decoded by only two receivers located in or near Sydney and that resulted in a record to APRS-IS. One was my own station which decoded three packets, and VK2RHR-1 which relayed 16 packets.

Given the balloon’s flight, it is notable that it was not relayed by VK2AWM-1 (which was 40km closer), VK2RAG-1 and VK2RTZ-1 at Gosford and Newcastle, and at least four igates in Wollongong, Sydney and Newcastle. Continue reading Diagnosis of APRS reception problem

Appropriate setup of audio drive of an AFSK APRS FM transmitter is important to ensuring that the signal can be copied by all receivers in range.

Excessive audio drive results in a signal that cannot be decoded by some receivers event though it may be very strong.

The TNC-X does not have any facilities for producing steady tones for adjusting the tx audio output for the desired deviation level, so alternate firmware was developed solely for this lineup function. The regular MCU chip is replaced by the adjustment chip for the lineup then the regular MCU chip is reinstalled. Note that this is not an augmented version of the regular firmware, it is for adjustment purposes only… do not overwrite the original chip. Continue reading Audio level setup on TNC-X (MFJ-1270X)

This article shows how to analyse 1200Bd AFSK FM signals off-air to identify defects in setup that will degrade system performance, and the shared channel generally. Continue reading Are you getting the best performance from your FM AFSK APRS transmitter

Foxtrack is an inexpensive kit form basic APRS tracker, taking a GPS NMEA feed and producing audio frequency shift keyed output to key an FM transmitter. It incorporates a limited TNC function and some intelligent position reporting algorithms

Above is the top view of the Foxtrack PCB. Continue reading Foxtrak build

I recently built a FoxDelta FOXTRAK APRS tracker.

FoxDelta supply the FOXTRAK with firmware by DK7IN, but also recommend APRSTRACKER by PE1RXQ and PE1ICQ.

APRSTRACKER v0.11 was trialled as it offered promise of a better SmartBeaconing implementation and support for altitude, course and speed reporting. Continue reading Review of APRSTRACKER v0.11 firmware