With a temperature around 0 deg C I did a field trip today TXing on 8.76kHz VLF to test two things: (1) to check the rebuilt 4-5W TX based on the TDA2003 could be copied at moderate range and (b) to try out the new tuned preamp with earth electrode receive antennas and see how these compared with a loop. The usual first test site, a National Trust car park about 1.5km from home was chosen. Today it was totally deserted with more sensible people curled up in front of warm fires. Using the 80cm receiving loop or with the earth electrode antenna (electrodes placed about 13m apart) decent
copy was achieved in QRSS3, using Spectrum Lab this time rather than Spectran on the PC. For the earth electrodes I just used barbecue skewers pushed in about 10cm into the very cold ground. Reception was also possible with the two earth electrodes just 2m apart. The first picture shows the signal received with a loop. The second is with the earth electrode antenna on receive. The ground was covered in a thin layer of wet snow and results when the soil, and soil surface, are dry should be better on earth mode conduction using earth electrodes at each end. The roads in the Fens were too icy to try reception at a more distant point 5-6km away. Also, I need a much longer baseline earth electrode pair in the car in case this is needed at greater range.