Speaker cable and similar Figure-8 twin in various sizes is popular as RF transmission line, particularly with QRP operators, especially those operating portable in the field (eg SOTA activators). Indeed, SOTA seems to have triggered a revival in the use of these cables. With the large number of online recommendations, one could be forgiven for thinking that a dipole and feed line formed entirely from #24 speaker wire is the antenna of choice.
With that in mind, this article looks at the performance of Jaycar WB1702 speaker cable, 14×0.14mm conductors (#24) with PVC insulation, cost $0.50/m.
Continue reading Speaker cable as RF transmission line
Matched Line Loss (MLL) is the loss or attenuation of a transmission line terminated in its actual characteristic impedance, and usually give for some length, eg dB/100′, dB/100m, dB/m.
One method that occurs in ham radio articles is to measure the input resistance of a resonant s/c or o/c stub, and to calculate MLL as 8.686*Rin/Zo/length dB/unitlength. (This is not the only method, or even a good one, but it is commonly used.)
Continue reading Measuring matched line loss
Bench tested a DT750 on 3S, Afro30 with 2013-10-29_8c2cf42_comp_pwm, 11×4.5SF and Eagle datalogger. This motor is reported by some to be incompatible with SimonK.
Continue reading HK DT750 motor, Afro30 ESC and SimonK 8c2cf42/comp_pwm
G3TXQ has published (undated) a set of measurements on commercial windowed ladder line at Wet ladderline (accessed 10/01/14).
His measurements are of interest as there is a dearth of credible measurement data for these types of lines below 50MHz. Continue reading Windowed ladder line loss – G3TXQ
A new Hakko FG-100 arrived from China this week, the meter and pack of 5 sensors cost less than A$12 including post.
Continue reading Review of Hakko FG-100 soldering iron thermometer
This article describes a driver for flashing LEDs using a repurposed ESC.
Continue reading Flashing LED driver using an ESC
I measured 6 different ESCs (all different types) at 25° with a 16MHz ceramic resonator, and standard deviation was 1200ppm, or 0.12%.
Continue reading ESC ceramic resonator accuracy
Discussion with a correspondent recently ranged onto the effect of some conductor materials in antennas. This posting reports the feed point impedance and internal efficiency (meaning power not turned into heat in the structure divided by power input at the feed point) of a 160m half wave dipole (80m long, centre fed, 20m above average ground and using 2.6mm diameter single core wire).
Continue reading Wire dipole on 160m
I have been heard to refer to “Foundation watts”.
I made a little video to explain and demonstrate the concept.
Continue reading Foundation watts explained
Robert Nickels, W9RAN shows a design for an “8 element colinear vertical” for 1090MHz ADSB in QST Jan 2014 in his article Virtual Radar From a TV Dongle.
Continue reading Yet another dodgy coax collinear