28 Feb 2013

8.97kHz earth-mode tests with mag-mounted E-field probe

Today I started some tests at 8.97kHz with my mag-mounted E-field probe (EFP) on the car roof. As usual, the transmitter was my 5W QRSS3 beacon feeding the 20m spaced earth-electrode antenna in the garden.

The logical starting point was to drive to my usual "strong" test site 1.6km from home and compare signal levels on the usual 80cm square RX loop with that on the EFP.  For reasons I have yet to understand the signal was NOT copied, even on the loop! What I did see was what looked like an FSK telemetry signal, possibly from overhead power lines close to 8.97kHz. I've never seen this before. Anyone know what it is?

8.97kHz 5W earth-mode signal at 0.4km on E-field probe
I then drove to my new QTH (due to be occupied in about 4-5 months time) which is 0.4km from the TX and sat in the car in the drive with the iPod Touch 4g running SpectrumView software connected to the EFP. The antenna was a short 19 inch whip. Signals were copied quite well (see photo showing "3" from my callsign). The bandwidth on SpectrumView cannot be narrowed enough to optimally receive QRSS3 and results would be better with the PC set to 0.34Hz bandwidth.

Tomorrow I'll have to find out why I couldn't see my earth-mode signal at the usual test site on either antenna. I'm also going to do some /M reception at 8.97kHz using the E-field probe and laptop with Spectran set to 0.34Hz or 0.17Hz bandwidth. With a continuous signal I'll be able to log the signal level as I drive around the village and nearby.

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