One of my simpler projects, just three electronic components and 140 lines of code… an open squelch DCD (OSDCD) for Paccomm Tiny2 Mk2 . Continue reading Open squelch DCD for Paccomm Tiny2 Mk2
Hams often speak of inline RF wattmeters as being ‘averaging’, but are they? Continue reading Are inline RF wattmeters really averaging
Electrical safety testing of equipment is covered by AS/NZS 3760:2010 In-service safety inspection and testing of electrical equipment.
This article describes how to test earthing continuity of amateur equipment. It is only one of several tests described in (AS/NZS 3760:2010), but it is most relevant to ham equipment, especially so-called ‘boat-anchor’ equipment. Continue reading Earth continuity testing of amateur equipment
FoxDelta supplies a null modem adapter with their FoxTrak tracker. The null modem is used only during configuration.
The adapter is supplied with hex pillars (jack screws) on both DE9 connectors, which prevents the adapter being plugged directly onto the FoxTrak, or onto a PC USB-RS232 adapter with pillars. Continue reading Revision of FoxDelta null modem adapter
I have observed an apparent interoperability problem between FoxTrak tracker and Argent Data’s OT3.
Tests have revealed that two FoxTrak’s are not decoded by two OT3s. Continue reading Interoperability of FoxTrak tracker and Argent Data’s OT3 – Part 1
This article explains a method of setting the tx audio level of a Foxtrak using an SSB/FM receiver exploiting Bessel zeros to calibrate the modulator. Whilst the Foxtrak is used in this example, the method can be used with any tracker or TNC that allows single modem test tones to be transmitted. Continue reading Adjusting Foxtrak tx audio using an SSB/FM receiver exploiting Bessel zeros to calibrate the modulator
Some AFSK sources such as TNCs, APRS trackers etc do not have facilities for sending single modem tones for the purpose of level adjustment which must be done using data packets which are a complex arrangement of high and low tones. Continue reading Adjusting AFSK FM tx level using a PC oscilloscope
Hams have used 1200Bd AFSK FM as the physical layer of AX.25 for decades, though with variable implementation quality.
Whilst the AX.25 packet networks of yore have all but died, the protocol is currently used with APRS, and so the related issues remain relevant… well as relevant as APRS remains. Continue reading AX.25 1200Bd AFSK FM – to pre-emphasise or not
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
I noticed a number of unfamiliar call signs appearing on the aprs.fi info page as stations located near mine, and some clearly corrupted format.
These included VK2RR-1, VK2AW-1, VK2OM-9, VK2YGV9 to name just a few. Continue reading APRS call sign corruption at iGate