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. Last update: 16th February, 2014, 7:53 PM
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 … Continue reading Speaker cable as RF transmission line
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 … Continue reading Wire dipole on 160m