title: Frequency Response of an Agricultural Fence and the Implications for Data Transmission

authors: McMullan, Jonathon

subjects: Frequency Response

abstract: The electric fence has been used as a data transmission medium in Gallagher Products for a number of years. This has allowed the energizer to be remotely controlled and, with the current generation, to monitor the performance of the fence remotely. Very little investigation has been conducted into determining the optimum frequency bands to transmit in to give optimum performance. 

We propose that the fence spectrum be split into three frequency bands. A Fence Pulse Guard Band which extends from DC to 10 kHz, a Low Frequency Channel which extends from 10 kHz to 250 kHz, and a High Frequency Channel which extends from 250 kHz to 10 MHz. 

The fence frequency response is dependent on the length of the fence and is dominated by transmission line effects and radiative losses. For the test fence, the spectrum up to 250 kHz is flat without any frequency selective fading. Above 250 kHz, the spectrum is very unstable and the frequency selective fading can exceed 15 dB. Operating in this region requires an advanced system to utilise the available bandwidth.

The impedance of the human operator in the system is best characterised as a fractional capacitor in series with a resistor. Higher frequencies are attenuated less up to 10 MHz after which the impedance is dominated by the resistance.

The impedance of an insulating joint is best characterised as a capacitor in series with a resistor. Higher frequencies are attenuated less and are the preferred method for reducing the effect of insulating joints.

The Low Frequency Channel is suitable for less robust systems which cannot tolerate frequency selective attenuation. The High Frequency Channel is suitable for robust systems which prioritise performance.

We present a number of possible solutions for improving the efficiency of the modulation and error correction strategies. Solution 3 utilising Phase Shift Keying (PSK) with eight symbols and Trellis Code Modulation (TCM) is recommended as the first solution to be implemented and evaluated. A forward error correction strategy as outlined in Solution 1 is also recommended for implementation first.

This research suggests that the electric fence system could be significantly improved in performance and reliability using the methods mentioned above but at some cost.

text: Frequency Response of an Agricultural Fence and the Implications for Data Transmission The electric fence has been used as a data transmission medium in Gallagher Products for a number of years. This has allowed the energizer to be remotely controlled and, with the current generation, to monitor the performance of the fence remotely. Very little investigation has been conducted into determining the optimum frequency bands to transmit in to give optimum performance. 

We propose that the fence spectrum be split into three frequency bands. A Fence Pulse Guard Band which extends from DC to 10 kHz, a Low Frequency Channel which extends from 10 kHz to 250 kHz, and a High Frequency Channel which extends from 250 kHz to 10 MHz. 

The fence frequency response is dependent on the length of the fence and is dominated by transmission line effects and radiative losses. For the test fence, the spectrum up to 250 kHz is flat without any frequency selective fading. Above 250 kHz, the spectrum is very unstable and the frequency selective fading can exceed 15 dB. Operating in this region requires an advanced system to utilise the available bandwidth.

The impedance of the human operator in the system is best characterised as a fractional capacitor in series with a resistor. Higher frequencies are attenuated less up to 10 MHz after which the impedance is dominated by the resistance.

The impedance of an insulating joint is best characterised as a capacitor in series with a resistor. Higher frequencies are attenuated less and are the preferred method for reducing the effect of insulating joints.

The Low Frequency Channel is suitable for less robust systems which cannot tolerate frequency selective attenuation. The High Frequency Channel is suitable for robust systems which prioritise performance.

We present a number of possible solutions for improving the efficiency of the modulation and error correction strategies. Solution 3 utilising Phase Shift Keying (PSK) with eight symbols and Trellis Code Modulation (TCM) is recommended as the first solution to be implemented and evaluated. A forward error correction strategy as outlined in Solution 1 is also recommended for implementation first.

This research suggests that the electric fence system could be significantly improved in performance and reliability using the methods mentioned above but at some cost.

year: 2014

title: Glacial geomorphology, soil development and permafrost features in central-upper Wright Valley, Antarctica

authors: McLeod, M.

subjects: rock glaciers

abstract: We mapped surficial deposits, soils and permafrost features in the central-western Wright Valley, Antarctica, from Lake Vanda in the east to near the mid-part of the South Fork in the west. Outstanding features of the landscape include two large rock glaciers covering approximately 323 ha with a volume of 0.14 km3, and the sinuous Upper Wright III moraine in the South Fork with typifying yellowish brown (10YR 5/6) subsoil colours. Soil morphology and weathering stage indicate the features are early Quaternary age and younger than Alpine III deposits. Soils are dominated by sodium and chloride ions, and the total salt content increases with age except where profile soil water is recharged either by subsurface flow from streams, melt water production at high elevation or sporadic surface flow. Ice-cemented permafrost at less than 70 cm depth is common, being associated with relatively young alluvial soils of the Onyx River, and with soils on the steep slopes of the south valley wall near the Dais where melt water from high elevation recharges soil water.

text: Glacial geomorphology, soil development and permafrost features in central-upper Wright Valley, Antarctica We mapped surficial deposits, soils and permafrost features in the central-western Wright Valley, Antarctica, from Lake Vanda in the east to near the mid-part of the South Fork in the west. Outstanding features of the landscape include two large rock glaciers covering approximately 323 ha with a volume of 0.14 km3, and the sinuous Upper Wright III moraine in the South Fork with typifying yellowish brown (10YR 5/6) subsoil colours. Soil morphology and weathering stage indicate the features are early Quaternary age and younger than Alpine III deposits. Soils are dominated by sodium and chloride ions, and the total salt content increases with age except where profile soil water is recharged either by subsurface flow from streams, melt water production at high elevation or sporadic surface flow. Ice-cemented permafrost at less than 70 cm depth is common, being associated with relatively young alluvial soils of the Onyx River, and with soils on the steep slopes of the south valley wall near the Dais where melt water from high elevation recharges soil water.

year: 2008

title: Ko tōku ingoa ko Ripeka - My name is Ripeka

authors: Waitoki, Waikaremoana

subjects: Wahine

abstract: This book is organised around Ripeka and her family's story. The events described in her story reflect the lives of several wāhine, tāne, rangatahi and tamariki who have been involved in psychological services.

text: Ko tōku ingoa ko Ripeka - My name is Ripeka This book is organised around Ripeka and her family's story. The events described in her story reflect the lives of several wāhine, tāne, rangatahi and tamariki who have been involved in psychological services.

year: 2016