To compare with the K9AY loop i made a small active antenna to the concept of PA0RDT http://yu1lm.qrpradio.com/pa0rdt%20whip.pdf I used a strip of double sided copper clad epoxy print 200x30 mm. The amplifier is a FET U310 and 2N3053 emitter follower. This small capacitive antenna did fit in a cycle bidon (bought on the Alp de Heuz once..) Interesting this antenna is only picking up the Electrical-field. It is also a good RFI sniffler. I used a relative big pickup plane of about 3x20cm at the risk of IMD but i wanted to compare this E-field antenna on the 137kHz and 500kHz bands. It works but the DCF39 TX at 138.9 kHz is about 30B stronger on the K9AY Loop. I have to check that out the difference should not be that big. That was at the low position (top picture). I moved it on top of the house about 8m a.g. Now DCF39 138.9 is s9+30 the difference ...
Ham radio in JO33hg31 53.15N 6.35E