A/B comparison test on 40m

An extended test comparing signals received in Florida from three nearby stations in Australia was conducted 21/12/13, a low elevation path of more than 14,000km.

The A/B comparisons were performed on statistics gathered from the W4HBK grabber, in this case measurements of the noise and each of two transmissions of 1min of steady carrier every 5min over a half hour.

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I2C – LCD interface – Type 1

A range of inexpensive serial to Hitachi style LCD interfaces are becoming available.

This article describes the settings for one sold by NYplatform on eBay (about $25 for 5 inc post at the time of writing – but they are getting cheaper). It uses the Philips PCF8574T I2C expander chip which is supported by the user developed Arduino LCD Library V1.2.


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Arduino RC servo ramp generator

In testing RC electric drive systems (ESC + BLDC motor), a repeatable scenario was needed to evaluate changes such as changes to commutation advance.

Often these changes have different impact under rapid acceleration or deceleration to slower changes.

This article describes a simple servo signal ramp generator based on Arduino hardware, in this case using an Arduino Nano but most Arduinos or clones could be used or adapted.

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Hobbyking A30 issues

The Hobbyking A30 is an economical power supply for LiPo chargers.

problems were noticed with a Turnigy Accel 8150 charger where the display became corrupted when the case was touched.


It turned out the output terminals of the A30 are isolated from chassis and power supply ground. Above is a scope capture of the voltage to chassis on the -ve output terminal, a common mode voltage of almost 300Vpk. Sure, it will not sustain much current, but it is potentially (pardon the pun) dangerous to any electronic equipment connected to the power supply.

In my case, I dismantled the case and bonded the -ve output terminals  to the mains connector earth terminal with a 2.5mm^2 insulated wire.

Whilst performing that work, I was concerned at the proximity of a large toroidal choke and the top cover with no intervening insulation. I applied some kapton tape to the lid to reduce the risk of problems.

Oh, and the power supply rattled when received. That was an extra case screw loose inside the power supply, and it had fortunately not yet caused apparent damage.

These power supplies are not intended as a general power supply for electronic equipment, and they do make a lot of radio frequency interference (RFI).

SAFETY WARNING: do not remove the covers or attempt such a modification unless you are competent to do so.

Some thoughts on zero crossing detection in sensorless brushless DC motors

A sensorless brushless DC motor senses motor position for the purpose of commutation timing by using the voltage induced in the unused winding at the time. Reliably sensing the motor position for a range of motor constructions and speeds proves a challenge.


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COMP_PWM and SimonK ESC firmware

COMP_PWM is an option on SimonK ESC firmware for sensorless brushless DC motors,

SimonK without COMP_PWM

Above is a capture of the waveform during two commutation steps where this FET is low side  modulated. You can see that when the low side FET turns off, voltage rapidly rises to just above battery as the energy stored in the winding inductance drives current through the high side FET body diode (which drops 0.7+V) and the other high side FET that is on.

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Australia’s NBN debacle limps on under a new government and new CEO

In an attempt to fix up a government orchestrated flawed regulatory and market environment that saw the dominant carrier digging its heels in to regain the right to install infrastructure that it was not required to share with competitors (ie, to allow it to reestablish a monopoly), the Labour government called for tenders from organisations to provide a National Broadband Network on its terms.

No contracts were awarded, government decided the way forward was for it to own the access network, at least for the interim, and so return to the situation that existed prior to the partial privatisation of Telstra in 1997.

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IC-7000 current consumption

This article describes measurement of an Icom IC-7000 current consumption during SSB telephony transmission.

The capture is of an IC7000 running 100W PEP with compression off. I have read copy as loudly and consistently as I could with barely a breath, so it is an overestimate of current consumption. There was small ALC deflection, but not so much as to effectively provide compression. Compression will draw higher current, depending on the level of compression. Note too, that like many Icom radios, the IC7000 draws a relatively high current key down with no audio (4.5A here).

IC7000 current consumption
IC7000 current consumption

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