The project has been expanded to accept a Dallas / Maxim DS18B20 1-Wire temperature sensor. The DS18B20 produces a digital output (signed sixteenths of a degree) has a range of -85° to 125°, accuracy of about 0.5°, and costs a dollar for bare chips, a few dollars for an encapsulated probe.
Above is a development prototype with the DS18B20 being heated by a small incandescent dial lamp to test function.
The ic9350 is protocol converter to permit use a Codan 9350 or 3040 automatic antenna with an Icom radio. Most Icom radios support the Icom AH-4 ATU, so the approach is to design a protocol converter that converts the protocol used by the 9350 and 3040 to the AH4 protocol to allow full integration with the Icom radios that support the AH-4.
In about 2009 I purchased a Uni-mig Jasic 200A TIG welder (though these are sold under many brands).
The welder came with unusual 2 and 5 pin connectors for the torch trigger switch and an optional pedal. The optional pedal was quoted at around $500, probably partly as the seller had locked the market up with the unusual connectors. (I note that the XS12K2P etc connectors are now available on Aliexpress.)
There is no standardisation of these connectors, but the pedal internals are pretty common. A quite common configuration is a 2 pin Foster (microphone) connector for the trigger switch and 3 pin Foster (microphone) connector for the current pot.
The loop appears to be made from 7/8″ copper tube, and is 7′ in diameter. He estimates its efficiency to be 66% and initially reports I’ve got it less than 4 feet above ground yet it tunes flat to 1.1>1 with roughly 10kHz bandwidth.. Curiously, 10kHz is the result calculated by AA5TB’s spreadsheet, though I have written elsewhere it is deeply flawed (Small transmitting loop calculators – a comparison).
Let us assume that these figures are correctly reported, and that the unqualified bandwidth means the half power bandwidth of a matched loop.
We can estimate the efficiency of a Small Transmitting Loop (STL) in free space.
Before getting excited about the results, let us question the validity of the model. There are three important factors that question the validity of the model:
The IC-7300 is a transceiver where all heterodyning oscillators are derived from a single master oscillator.
This type of radio makes for very easy checking and calibration of frequency accuracy.
The video below demonstrates the technique.
The video used a local GPS disciplined source at 50.1MHz. The frequency was chosen to provide the greater resolution in setting the oscillator, though setting it to within 1 part in 50,000,000 or 0.02ppm is better than the stability of the oscillator (specification is 0.5ppm or 5Hz at 10MHz).
Any accurate known reference can be used, it could be WWV or the like, or even a MW broadcast station, though an accurate signal at 10MHz or higher is better.
The technique can be applied to the much older IC-7000, and many transceivers released since then, of various brands. The important thing is that ALL oscillators are derived from a single master oscillator.
This article explains the ‘demagnetisation’ issue that challenges sensorless brushless DC drives that depend on Zero Crossing (ZC) detection to synchronise the next commutation phase.
Above is a scope capture the ‘A’ terminals of a Multistar 4220-650Kv with 1045SF propeller running at about 50% throttle on 3S (about 4000rpm). The motor is quite lightly loaded for the purpose of illustration. The motor drive is low side complementary PWM modulated, and drive is advanced by 15° and the FETs are all N-FETs.
We will focus on the detail starting at about 5 divisions on the time axis (2500µs). The explanation will detail behaviour of the ‘A’ section of the drive, but the same thing happens on the B and C sections which follow each 120° electrical later respectively.
I recently purchased a Surecom SW-102 VSWR meter. It looked a little like a supercharged RedDot copy.
Above the Surecom SW-102 VSWR meter with backlight and photographed under normal interior lighting. The display lacks contrast, and overall is difficult to read due to size of text, fonts used, and lack of contrast. (The pic is taken with a screen protector installed, but the evaluation is based on the bare meter with original protective film removed as it degraded readability.) Continue reading Surecom SW-102 VSWR meter review
A ham in search of good advice asked in QRZ forums dB, dBi, and dBd: I have a loose grasp of these terms and their relationships. Is there any way to rule of thumb the gain of any antenna over a dipole over earth?
This is a report on a series of tests performed on a Hobbyking Multistar 4220-650Kv sensorless brushless DC motor.
Above, a top view of the bare motor. It is a 12S16P disc form or pancake form motor, a style that is very popular though inclined to sync problems.
Above, the underneath of the bare motor.
The prop adapter is not shown, it had almost 1mm runout and would need to be replaced to actually fly the motor as propeller induced vibration would be unacceptable.
The motor would appear to be similar to the Hengli 42 20 650Kv, in fact so similar that it would seem possible, even likely that Hengli is the OEM.
Induced voltage waveform
The motor was driven at 970rpm and the voltage between two motor wires observed on a scope.
The line-line voltage is the sum of two phase voltages, one of which is a time delayed copy of the other and whilst the resultant is sinusoidal when the components are purely sinusoidal, the transformation is less obvious for complex waves such as shown above.
The phase voltage is of interest as it drives the sense process that provides motor timing crucial to commutation.
Direct measurement of the phase voltage using a star of 12kΩ resistors to establish a neutral reference yields the waveform above.
The induced voltage waveform somewhat the result of the 12N16P configuration. Period of the waveform is 7.7ms, equivalent to 60/0.0077=7790erpm indicating 7790/970=8 pole pairs or 16 poles. Continue reading Hobbyking Multistar 4220-650Kv