Re: LF: Re: 1.095kHz earth mode test at 6km

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Thanks Mal. Encouraging as ever.

On 8 August 2011 18:44, mal hamilton <g3kevmal@talktalk.net> wrote:

To day my lawn is covered with MOLE MOUNDS of soil. As far as I can see all you are doing is driving the MOLE population up NORTH

QRP es Underground earth mode induction seems to achieve little for big effort !! The local Music Rave can be heard 19 miles away

in Audio mode using loudspearkers, a 2 Kw amplifier and an  Appliance Operator !!!

 

G3KEV

 

 

 

----- Original Message -----

From: Roger Lapthorn

To: rsgb_lf_group@blacksheep.org

Sent: Monday, August 08, 2011 2:45 PM

Subject: LF: 1.095kHz earth mode test at 6km

Today I repeated the earth mode (through the ground) "long carrier" test of 17.7.11 this time at 1.095kHz rather than 8.760kHz. The same test location was used in the fens not far from the River Cam. This is now a very long way from home! As before, I got my XYL to cut the carrier for periods of 1 or 2 minutes to positively identify my signal. I need to automate this so she can continue to do the gardening....

4 different receiving antenna arrangements were tested, using my low impedance MPF102 tuned preamp into the PC:

(a) an earth electrode pair parallel with the road,
(b) an earth electrode pair diagonally across the road,
(c) a single turn loop in the road, and
(d) a 30t 80cm diameter loop at the edge of the road. 

Best results were with (a) and (d). With (b) there was no detectable. 

At 1.095kHz the signal was again around 10dB S/N in 11mHz bandwidth on (a) and (d) and marginally weaker on (c). This is a similar result to 8.76kHz although I was expecting the signal to be stronger at this lower frequency.  I'm now tempted to do an earth mode test at a higher frequency, possibly 17.52kHz which I can still see with Spectran and Spectrum Laboratory and I can derive with my 4060 divider circuit. Using earth mode I believe I'll still be legal as very little radiated signal can be present.

The image attached shows the signal with the RX earth electrodes parallel to the road, i.e. set-up (a), at a distance of 6km from the home QTH where the TX was running 5W into 20m spaced earth electrodes.

73s
Roger G3XBM

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