> On 2 June 2014 04:18, John Coppens wrote: > > >> You have to be on resonance, as this is the point where the current in >> the >> antenna will be maximum > > > Lonnnnnnnnnnnnnnnng ago (counts on fingers (mentally) ... about 46 years > ...) : > > Best signal appeared to be achieved by maximising the blue glow in the > glass of the '807 final tubes. > This was very slightly off plate current resonance dip. > Those not using 807's will not have this inbuilt capability :-) I remember the same thing for 4-400s and 833s. To me, the physical configuration of an antenna results in a certain radiation pattern and a certain impedance (R + jX). The R is the radiation resistance. You want to get as much power as possible into this. As an antenna gets shorter, it becomes more of an isotropic radiator and the radiation resistance goes down. The reactance is zero at resonance. As R gets very low, you see losses in other resistances in the circuit (in AM broadcasting, the ground system losses become significant). As others have pointed out, if the reactance is very large, the voltage across that reactance will have to be large to get sufficient current through the radiation resistance. Most of my antenna experience is in the AM broadcast band (1MHz). An article on use of the 90 degree network in AM applications is at ouise.hallikainen.org/rw/theory/theory13.html . Harold --=20 FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available! Not sent from an iPhone. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .