LOW FREQUENCY MAGNETIC RADIO
PictureRadiolocating an autonomous vehicle under sea ice in Antarctica
 
 Theory, practice, advice, radio kits and circuit boards, volunteer and commercial services, and other cave related electronic stuff.
My old website http://radiolocation.tripod.com is no longer maintained but has useful information not given here.  More information will be added here from time to time.
IMPORTANT NOTE: My email address has changed.  See the CONTACT page!!!!!
This site was last updated on May 11, 2025.  There are some new technical articles
For the latest information click on the links below:

New May 2025!  Article from a Powerpoint presentation on cheap and easy TTE texting using the QDX-M  radio and RadioMsg software.
New November 2024! The PDF on constructing the Basic-2 Radiolocation units now includes info on making one of the units just a receiver and the other just a transmitter. This simplifies construction and use for those who just need one-way Radiolocation.
New June 2024!  See the Technical Articles page for a link to all 29 older Issues of Speleonics (1985-2013), publication of the NSS Communications and Electronics Section. Speleonics 30 has just been added with presentations and Section notes from 2014 - 2017.
New April 2024!  See Ian Drummond's article in CREG Journal 124 about an inexpensive transceiver kit that can be customized to do Through the Earth texting on the 2200m ham band (137.5KHz) with small loops and an Android smartphone with an existing free app. The radios are the QDX-M from QRP-Labs.com. His initial tests have been with laptops. I am actively working with these radios and cheap ruggedized tablets. Others are looking into Raspberry-Pi with a different version of the software. Also see his article on Long Range Radio.
New Feb 2024! Victor Porto has created an Android app that calculates radiolocation depths for both the field angle null and ratiometric field strength (2 heights above ground) methods. Victor has placed the app, called Depth Calculator, in the Google Play Store, where you can download it to your Android device.
The Ultraphone, a high performance single wire telephone for expedition use. They are in use on Bill Stone's Cheve Mexico expedition Jan-April 2021.  I plan to offer PC boards and possibly kits later this year.
The Basic-2, a simple, low cost, 1750Hz thru-the Earth radiolocation and 2-way morse code communication radio for beginners or demonstrations.  A complete kit (except for the loop antenna) is available.


The Double-Quadrature (DQ) 3496Hz receiver.  These are the most sensitive radiolocation receivers available.
Circuit boards and certain hard to find parts are available.

The Class-E 3496Hz underground Radiobeacon for use with the DQ receiver.  This simple and efficient design can be easily adapted to large and small loop antennas and multiple power levels.  Circuit boards and certain
hard to find parts are available.

Thru-the-Earth low frequency single-sideband voice communications using a transverter with portable HF Ham Radios.

Technical articles detailing experiments in thru-the-earth text and voice communications, cave surveying, and other electronic topics of interest to underground explorers.  Some are derived from PowerPoint presentations given at the annual National Speleological Society annual convention.