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