15/16 ips Operation of the Precision Instrument Company Model Pl5100 Tape Recorder to Record the Standard (30 Hz) NCER Seismic Data Multiplex System

Introduction

In recent months the need has arisen to record special seismic networks consisting of a dozen or more standard NCER seismic systems telemetered to a central collection point on a reliable, portable, low-power tape recorder. Because of its simplicity and the ease with which it can be adapted for the purpose, the PI 5100 field recorder should be considered for such use. In the tests described here, a PI 5100 was speeded up to run at 15/16 inches per second (ips) and signals from the standard multiplex system test modulator bank¹ were recorded on one tape track by means of a simple, improvised AM record amplifier. The results of these tests are extremely encouraging: the dynamic range of the system when played back on the Bell and Howell Model 3700 B reproduce machine, with subtractive compensation, is nearly as high as for the system employing the B&H 3700 B for recording.

These notes indicate the principle employed to speed up the recorder, outline the circuit required to drive the tape heads in the AM record mode, and describe the tests carried out to evaluate the system’s performance.

¹ Eaton, J.P., 1975, Notes on some experiments on the application of subtractive compensation to USGS seismic magnetic tape recording and playback systems: U.S. Geological Survey Open-File Report 75–663, 36 p. (Available at http://pubs.usgs.gov/of/1975/0663/.)

First posted June 6, 2012