There are many causes of zig zag errors in APRS tracks, and they fall generally into two main categories: incorrect positions (ie the tracker was never there); and correct positions with incorrect timestamps. The first is common and has a number of causes, but principally defects in software used in iGates, most of which is … Continue reading Zig zags in APRS tracks
Small Transmitting Loops (STL) usually require a capacitor to tune the loop to resonance for ease of efficient matching. For an efficient STL that can handle moderate power, the capacitor must withstand extreme voltage, and must have extremely low equivalent series resistance (ESR). (Straw 2007) describes the so-called ‘trombone’ capacitor which is attributed to Bill … Continue reading Trombone capacitors in Small Transmitting Loops
A correspondent asked about whether the proprietary copper clad VHF whips are some kind of marketing ploy. Lets consider a quarter wave whip for the 2m band. Made from 2.4mm stainless steel, it should deliver lowest VSWR50 at about 483mm in length. The properties of stainless steel whips will vary, but lets consider the case … Continue reading Are copper clad VHF whips a marketing ploy
I was intrigued by the seemingly endless stream of stories of woes with the DYS SN20A (eg RCTimer / DYS Mini SN20a / SN30a / SN40a esc), so I purchased one to see if they are all bad. Of course, impressions of a sample of size one are of somewhat limited value, but it seemed … Continue reading DYS SN20A out of the box
Several correspondents have asked about the application of Calculate small transmitting loop gain from bandwidth measurement to the helically loaded small transmitting loop. The helically loaded small transmitting loop appears to be the invention of K8NDS and is described at Stealth Antennas for the Radio Amateur and (K8NDS nd). It may not be a novel idea … Continue reading Helical loading and Calculate small transmitting loop gain from bandwidth measurement
I recently travelled to Wollongong and back by a round trip, partly to evaluate APRS coverage on the Picton Rd. Above is a screenshot of the 140km track. Last update: 25th August, 2015, 7:58 AM
There are a number of USB-RS232 adapters available, among them Silabs, FTDI, Prolific and WCH. The Silabs CP series adapters have been reliable but not very widely used. The Prolific adapters are, well, prolific… but given their major compatibility problems and poisoned drivers, they are not a good choice. FTDI was a good choice until … Continue reading A tale of two USB-RS232 adapters
I have a little RC-4 temperature logger which has been a really handy device for ensuring that our freezers are cold enough, but no colder. The RC4 has an internal sensor and is supplied with an external sensor that plugs into a 2.5mm TS jack on the side. This article explores an alternative sensor that … Continue reading RC4 thermistor characterisation.
This Feb 2012 article has been copied by request from my VK1OD.net web site which is no longer online. The article may contain links to articles on that site and which are no longer available. Many designs have a ‘balanced output’ or an option of a ‘balanced output’, but what does that mean, and are … Continue reading Balanced ATUs and common mode current
After almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers. The plan is to investigate two streams, one ST Microcontoller based and one ATMEL based, both ARM architecture. Last update: 17th June, 2015, 6:04 PM