PKD telemetry

At the time the station PKD was installed in 1996, continuous telemetry from the site was achieved by interconnection of a digital spread spectrum radio (900 MHz) with the frame-relay circuit at Carr Hill. Radios in this spectrum have the advantage of not requiring federal licensing or permits and the BSL installation in 1996 was the first use of such equipment in Parkfield. Since the initial installation, at least two other investigating groups in Parkfield have installed similar radios, ultimately causing interference and a reduction in data bandwidth.

In December of 2003, BSL and USGS engineers went to Parkfield to coordinate frequencies, align antennas, and replace and move radio equipment in order to minimize future interference. Over two days, the telemetry path from the PKD vault to the Carr hill site was redirected to a repeater site operated by UCSD. RF signal levels were tested and confirmed. By January 2004, however, the signal levels on the new path had faded as much as 20 db, apparently due to the increased water absorption by vegetation. During a January trip by BSL engineers, antennas were once again redirecting the data path directly to Carr Hill. Unfortunately, that solution was short lived as the signal level fell again and faded more than 10 db in the following two weeks. During a third trip, BSL engineers installed a solar-powered radio repeater, which operated satisfactorily through the dry summer months of 2004.

For a more robust solution, the BSL sought and obtained permission from a private landowner to install a solar-powered repeater at a different site. In December of 2004, engineers from BSL successfully installed the new repeater. This installation worked reliably through both winter and summer months.

Berkeley Seismological Laboratory
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