Introduction

A case of DVB-TV [1] tuner based software defined radio as a ground receiver for meteorological balloon borne sensor instrumentation, often termed as radiosonde [2] [3], is presented. These tuners DVB-TV are based on Rafael Microelectronics make R820T and Realtek make RTL2832U chipsets and popularly known as RTL-SDR[1]. Proprietary hardware receiver or universal software radio peripheral (USRP) are commonly used as meteorological balloon telemetry receivers. Most of these receivers are expensive and are suitable for bench-top applications. In addition a small, mobile, low power and low cost ground receiver is desirable for remote location radiosonde launch campaigns. Further a mobile receiver can be of great use if tracking and recovery of expensive radiosonde payload such as Ozonesonde, frost point Hygrometer etc. is required. Often recovered payloads are reused to cut down the launch cost.
In this paper an affordable low cost receiver for hobbyist and student community is presented. Figure 1 shows the block diagram of the proposed RTL-SDR based receiver system. Radiosonde transmitter parameters and characteristics are well defined in ITU-R SA.1165-1, 2004 [5]. Typical parameters of the telemetry system for radiosonde application are as given in Table 1. Most of the present day radiosonde uses Gaussian Frequency Shift Keying (GFSK) to transmit the sensor data in the frequency range of 400.15-406 MHz. Often Reed-Solomon error detection and correction technique is also applied to improve the link performance.
Table 1: Radiosonde Telemetry specifications