I had a contact with a newcomer recently, and struggling to hear him, I learned that he was using the 3030 antenna described in the WIA’s “Your entry to amateur radio” 2nd ed, the Foundation licence training manual.
Foundation manual on power measurement
My article Foundation watts explained triggered some discussion on the thorny issue of compliance with power limits of the LCD.
One correspondent was confident that the Foundation candidates are properly trained, which leads to examining the training materials.
SimonK ESC FW – test of commit 8873df24 – #3
SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this F330 quad with Multiwii 2.3 FC, 3S, Hobbyking D2830-11 motors and 8×4.5 SF propellers.
Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.
SimonK ESC FW – test of commit 8873df24 – #2
SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this X450 quad with APM FC, 3S, Hobbyking D3530-14 motors and 11×4.5 SF propellers.
Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.
Tricopter build – 20140201
Tests on the tricopter using a data logger to capture motor speed, current and pack voltage gives an insight into platform operation.
Above, data capture from the tricopter on 3S. The datalogger adds 50g mass.
The plot shows the device hovering at about 5000rpm and 10.8A at 11V. Two WOT ascents were made to check acceleration and motor recovery during closed throttle descents. From idle, it takes about 500ms to accelerate to hover rpm. This test was repeated and the motor reliably restarted every time and the tumbling craft stabilised quickly. A set of 12×4.7SF props has been ordered to try at 3S to more fully load the motors.
Similar tests were conducted also on 4S, and peak current on WOT was 80A on 15.5V for 8500rpm. Operation on 4S would provide sufficient lift to carry a camera payload, but WOT operation exceeds the motor’s continuous current rating.
Tricopter build – 20140131
The tricopter project lumbers on, delayed by faulty parts.
The recommended tail servo, a Hobbyking HK 922 Metal Gear Digital Servo, failed. It had a rough spot at about 70% of its range from new and which became worse quite quickly until the motor had insufficient torque to overcome it.
Cobwebb antenna impedance matching scheme
From time to time, correspondents have asked how the Cobwebb antenna works, and particularly how the impedance matching scheme works.
Firstly, what is the Cobwebb?
It is an innovative antenna for small spaces, quite compact and as I recall originally intended to cover five amateur bands from 20-10m.
Measuring common mode current on coax
In Common mode current and coaxial feed lines, I mentioned that common mode current is easily measured,
Common mode current and coaxial feed lines
An antenna feed line is intended to convey energy from the transmitter to the antenna, and usually without giving rise to radiation itself.
The term “common mode” comes from consideration of the currents on an open two wire line, and it refers to the net or unbalance current, ie the current that would give rise to external fields, to radiation.
This article looks at the equivalent common mode current in a coaxial transmission line.
RG174 for portable HF operation
There are frequent recommendations of RG174 for portable stations (eg SOTA), usually running QRP, principally because it is light and easy to wind up into a small package to fit into a pack. RG174 commonly uses silver coated steel (SCS) centre conductor, sometimes copper clad steel (CCS), sometimes copper.