136kHz Direct Conversion Receiver by IK2PII
I describe a simple direct conversion receiver, thinked for QRSS and DFCW communications, as companion of ARGO or SPECTRAN programs. The receiver is useful also as portable receiver, fast turn-on receiver for a quick look an the band or as very low cost (and performances) spectrum analyzer.
http://www.qsl.net/ik2pii/lf/dcrx136.htm

136kHz Converter by LA8AK
Picture showing the latest version of 136kHz converter. In this business you just can't get too many input/output connectors. Installed some BNC connectors, but later preferred Conhex, because they are free and available on lot of surplus equipment and cables.
http://www.noding.com/la8ak/L1.htm

"Passive converter" using HCMOS switch by SM6LKM
This converter uses a 74HC4053 as the mixing element. It simply reverses the polarity of the incoming RF at the local oscillator rate. The principle is the same as in the case of diode ring mixers.
http://home4.swipnet.se/~w-41522/lfconv/lfconv.html

VLF/LF to 28.5 MHz Receiving Converter by DF3LP
This converter is one of my early projects. It is built using "ugly style" in a small metallic case usingBNC for in- and output connection including some internal shielding of the crystal oscillator.
http://www.qsl.net/df3lp/projects/lfconv/index.html

VLF nach KW-Konverter durch DG7XO
Dieser Converter stammt von der Homepage http://www.radiosky.com ab.Ich habe dazu ein Layout für ein OM aus unserem OV gemacht, dass ich auch hier zur Verfügung stellen möchte.
http://www.dg7xo.de/selbstbau/vlf2kw.html

136kHz L.F. Pre-amplifier by GØMRF
This circuit is based on a design by Dave Pick G3YXM and was jointly redesigned in 2003 after the original coils and polystyrene capacitors were made obsolete.
http://www.g0mrf.com/preamp.htm
 

Field strength meter for the 137 kHz band by PAØSE
The power radiated by an antenna is equal to the radiation resistance multiplied by the antenna current squared. Measurement of antenna current can be done in the 137 kHz band by for instance a thermocouple ammeter or other means.
http://hamradio.nikhef.nl/tech/lf/fsm/pa0se.htm