Simple ADS-B Receiver

Description: The new project utilizes old analog satellite receiver tuners that require modifications to disable the AFC and set the AGC to maximum gain. The output generated is a 480 MHz IF signal. The IF converter may consist of a satellite receiver with a 70 MHz IF output or a TV receiver/converter adjusted for a 1090 MHz input, with the IF extracted post-SAW filter. The TV converter option provides excellent results, while the satellite receiver at 70 MHz also performs adequately but necessitates a custom-made filter to reduce the IF bandwidth to approximately 5 or 6 MHz. A simple "Spider" antenna designed for 1090 MHz, paired with a robust satellite line amplifier, is enclosed in a watertight container. Approximately 30 meters of cable connect this antenna to the receiver. The receiver is a modified FUBA unit, configured to operate with a local oscillator of 1126 MHz, with the PLL disabled due to its incompatibility at this frequency. The input signal is further amplified by an additional amplifier. The first BF494 transistor amplifies the IF, while the second BF494 serves as a buffer for the signal, which is then demodulated. The quality of the demodulated signal can be fine-tuned by adjusting the bias of the BAT43 diode.

The project is centered around repurposing existing analog satellite receiver tuners, which involves specific modifications to optimize performance for desired signal processing applications. The Automatic Frequency Control (AFC) is disabled to ensure a stable frequency lock, while the Automatic Gain Control (AGC) is set to maximum gain to enhance signal reception. The output of the project is a 480 MHz Intermediate Frequency (IF) signal, crucial for further processing.

The choice of IF converter is flexible, allowing the use of either a satellite receiver with a 70 MHz IF output or a TV receiver/converter that has been tuned to accept a 1090 MHz input. The configuration of extracting the IF signal after the Surface Acoustic Wave (SAW) filter is essential for filtering out unwanted frequencies and ensuring clean signal processing. The TV converter is noted for its excellent performance, while the satellite receiver option requires additional filtering to reduce the IF bandwidth to around 5 or 6 MHz, which is critical for minimizing noise and improving signal clarity.

The antenna system consists of a "Spider" antenna optimized for 1090 MHz operation, which is known for its compact design and effective radiation pattern. The inclusion of a high-quality satellite line amplifier enhances the signal strength before it travels through approximately 30 meters of coaxial cable to the receiver. The receiver, a modified FUBA unit, operates with a local oscillator set to 1126 MHz, with the Phase-Locked Loop (PLL) disabled to accommodate the specific frequency requirements of this application.

Signal amplification is achieved using two BF494 transistors; the first serves to amplify the IF signal, while the second acts as a buffer to ensure signal integrity before demodulation. The demodulation process converts the IF signal into a baseband signal, which can then be processed for further applications. The performance of the demodulated signal is adjustable via the biasing of a BAT43 diode, allowing for fine-tuning of the signal quality to meet specific project requirements. This comprehensive setup exemplifies a practical approach to utilizing existing technology for innovative signal processing applications.The new project uses old analog satellite receiver tuners that have to be modified so that the AFC is disabled and the AGC usually set to maximum gain. The output is the 480MHz IF signal. The IF converter can be for example a Satellite receiver with 70 MHz IF output or a TV receiver / converter tweaked to 1090 MHz input and the IF taken after the

SAW. The TV converter solution gives excellent results and the satellite receiver at 70 MHz works just as well but need a handmade filter to filter the IF down to about 5 or 6 MHz bandwidth. A simple "Spider" antenna for 1090 MHz with a good Satellite line amplifier like the xxx is housed in a watertight container.

About 30 meters of cable link this antenna to the reciever. The receiver is a FUBA xxx modified to run with an Lo of 1126 MHz and the PLL disabled as it does not work at this frequency. The input signal is again amplified by a xxx amplifier. The first BF494 amplifies the IF and the second BF494 buffers the signal which is then am demodulated.

The quality of the demodulated signal can be adjusted by offsetting the bias of the BAT43 diode.