I couldn’t help myself… I bought a Raspberry Pi 2 (RPi2) to evaluate.
The RPi2 has 1GB of main storage (double that of the earlier RPi B+), and a 4 core 900MHz processor against a single core 700MHz process in the the RPi B+. Continue reading Raspberry Pi 2 initial impressions
Further to AIM 885 produces internally inconsistent results…
A new release, AIM885A appeared recently.
In the common theme of one step forward, two steps backwards, this version produces error popups when started.
The above popup appears twice when starting AIM885A. Just another symptom to undermine confidence in the system. It doesn’t make sense to me, and the program appears to otherwise start and run. Continue reading AIM 885A produces internally inconsistent results
This article builds on Accuracy of AIMuhf system – AIM865A vs AIM882 on a ferrite cored inductor by adding a measurement using AIM885 of the same test inductor.
Above is the test inductor. It comprises 6 turns of 0.5mm PVC insulated wire wound on a BN-43-202 binocular balun core. Continue reading Accuracy of AIMuhf system – AIM865A vs AIM882 vs AIM885 on a ferrite cored inductor
New features in version 885 is
Fixed “Refer to Antenna” function… so lets check it out.
The AIMuhf was calibrated using the supplied OSL components and AIM885.
Above is a sweep of a 1.05m length of Belden 8262 (RG58C/U) cable (with o/c termination) attached to the AIMuhf. Continue reading AIM885 Refer To Antenna checkout
Some time ago I published a calculator for estimating the impedance of RF inductors on toroidal ferrite cores (Calculate ferrite cored inductor).
The calculator (input form above) use the core dimensions and complex permeability as the basis for calculation.
There are some popular cores that are not simple toroids and so not suitable for direct use with that calculator. For these cores, a practical method is to measure the inductance constant Al (inductance of 1 turn in nH) at low frequency (where µ=µi), and using the µ’,µ” characteristic from the datasheets, to calculate the impedance at the desired frequency. Note that µ’,µ” are usually frequency dependent for ferrite materials. Continue reading A new impedance calculator for RF inductors on ferrite cores
I received a sample of speaker wire from a correspondent who asked me to characterise it.
Even if I had the time, a 50mm sample isn’t sufficient to characterise in a meaningful way… but let’s have an abbreviated look which will highlight the pitfalls of this stuff.
First thing to do is measure the conductors, stranding and diameter. There are 14 strands and several measurements fall just below 0.15mm diameter. This is probably nominal 0.15mm with new drawing dies which are a little undersize. Continue reading Speaker wire is so popular as an RF transmission line
In other posts, I have commented on the apparent inconsistency of AIMuhf measurements.
One of the devices I often wish to measure is a ferrite cored choke such as those used for a Guanella 1:1 balun. A small test inductor was made to provide a common device for measurement across instruments, and versions of software, though small, it has similar characteristics to the larger inductors more commonly measured.
Above is the test inductor. It comprises 6 turns of 0.5mm PVC insulated wire wound on a BN-43-202 binocular balun core. Continue reading Accuracy of AIMuhf system – AIM865A vs AIM882 on a ferrite cored inductor
The Slot.it CA20A is a sidewinder configuration with the Mabucci style MF08 motor with extended shaft at both ends. The shaft ends extend out to about the mid point on the rear tyres with about 1.5mm clearance to the tyre.
The supplied PT32 tyres are quite elastic, and fly off the rim at high speed, making contact with the extended motor shaft and gouge the tyre, not to mention slowing the car. Continue reading Slot.it CA20A rework
I couldn’t resist the Hobbyking Swap Dawg as an opportunity to play with SimonK ESC firmware with forward / reverse enabled.
ESC selection and implementation
I selected a Hobbyking F-30A ESC, which might seem a bit of overkill but it is a closed air space which reduces its dissipation capacity. The F-30A have proven themselves reliable with SimonK on a range of BLDC motors. Continue reading Hobbyking Swamp Dawg build – #1