Because of the better signals, I have switched the circuit board to PBA-MLA4. It became clear that at LF an active whip is a capacitance coupled to the electric field. Results were encouraging and the whip length could be reduced from 100 cm to 30 cm without loss of performance. Tests were performed using an active whip antenna, designed by G4COL. However, I typically use the Mini-Whip in mobile operation (please see “ my antenna” page) and this is the best antenna for the car SWLing as it is very small and covers wide bands, without the effect from engine noise. The Mini-Whip antenna is a type of vertical antenna that is powered on top, where the voltage is very high and the current is very small.The impedance is very high and is perfectly tuned to. Hence an electric field antenna was called for. Results were encouraging and the whip length could be reduced from 100 cm to 30 cm without loss of performance. In the above videos, the Loop antenna actually performed the best. Zanzibar Broadcasting Corporation (Swahili) 11735 kHz In most cases, PBA-MLA4 gave stronger signals than the original PA0RDT type. The following videos are all Perseus spectra when compared between 1) PBA-MLA4 Mini-Whip, 2) PA0RDT Mini-Whip, 3) LZ1AQ’s AAA-1 Active Loop, and 4) back to PBA-MLA4 Mini-Whip, switching in this order about every 15 seconds. In the above photo, the lower one is another Mini-Whip based on the original PA0RDT’s design (also available in Japan as a kit), to use for comparison. It uses an op-amp IC chip instead of transistors. This looks a modified version of the famous PA0RDT Mini-Whip antenna. 2.0) Mini-Whip” antenna, developed by Hokushin Electronic Service in Japan (their Blog site to show this antenna is here, but only in Japanese). For LF it seems SNR is key and it isn't obvious that a bigger antenna or more gain will help.I am currently at my home country during the new-year holiday, and had a chance to test “PBA-MLA4 (rev. I also made a ferrite-sleeve-loop, and a ~1m diameter coax-loop, but haven't had time to test them properly. Anyway the mini-whip seems to perform quite well and is significantly easier to find space for than the 35-40m wire! For the TDF signal at 162 kHz the tuned long-wire provides almost the same signal as the amplified mini-whip. PA0RDT antenna (Mini-Whip) Information about the antenna The PA0RDT antenna is a very small antenna for the case you arent allowed or able to put a long wire antenna up in the air. The long-wire has a tuning coil for resonance at 136 kHz - so the comparison isn't entirely apples to apples. I just tested the original PA0RDT design against a long-wire (around 35m IIRC), looking at some LF time-code signals. There is an updated cricuit by PA0NHC that uses BF998 for the first FET: and also a version by RA0SMS, for sale on e-bay.
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