21 Oct 2010
Using the same TX output power (5W) and the same loop antenna I'm finding life is VERY much harder on 137.5kHz compared with 500kHz. Last night I was being copied right across Europe on 500kHz but tonight only 2 stations (best DX 69km) are able to copy me on 137.5kHz WSPR. The reason is simple: the radiation resistance is so much lower, so losses become more significant, and the ERP is very considerably lower. There is no doubt that to increase my "sphere of influence" on 137.5kHz I'll have to make some big improvements.