Mini-whip RX active antennas

These antennas can be very effective on VLF, LF and MF. They are extremely small but work every bit as well as big antennas. They are the best way to listen on these lower bands.

They are sometimes known as E-field probes (EFP). They work because external noise dominates. This noise decreases as the wanted signal decreases so actual S/N is just as good with a small antenna. This is not the case when the RX noise figure dominates. Often they are optimised for lower frequencies. With active antennas it is important to have good dynamic ranges.

See https://sites.google.com/view/g3xbm4/home/antennas/e-field-probe-efp . 

UPDATE 1253z:  Now 137kHz EFP on new site - see https://sites.google.com/view/g3xbm4/home/antennas/137khz-efp-rx-antenna .