Some years before, some experimental licences for ham radio below 9 kHz were issued in germany. Meanwhile this frequency range is free as the Bundesnetzagentur has confirmed last year.
Transmitter is an Präcitronic GF62 Level Generator actually at 8,79 kHz. PA is an old homebrew NF-Amplifier with 2x 2N3055 and about 40 Watt at 4 Ohm into a 100V ELA transformer. Antenna is a T-Antenne of 10m with 20m top capacity and poor ground.
Receiver is a portable sferics RX that I built some years before (AATIS). Unfortunately its whip antenne is highly influenced by trees and houses.
The fact that I can hear (!) my beacon in normal CW up to 100m in an city environment with a highly unmatched antenna makes me believe, that in a better environment and with a matched antenne and with help of ARGO one can make tests over longer distances. But even from my QTH in the city the ODX ;-)) surely can be improved.
The mean problem now ist how to match the antenna . . . - or using ground antennas vor TX, RX or both.
20 Feb 2010
This has just been posted on the LF reflector by DO1KHS. I wonder how many other people have experimented with communications at radio frequencies below 10kHz? If so, do share your experiences here. See also my website on the subject at http://sites.google.com/site/g3xbmqrp/Home/10khz