SDR Project: Pulling Satelite Images from NOAA Satellites

Excited to delve into more projects using my RTL SDR, I began my journey into pulling images from the NOAA Satellites. The prospect of capturing and decoding images directly from space definitely piqued my curiosity.

I read up a lot on different ways to accomplish this task along with the type of software I would need to use. I created an Ubuntu VM on my laptop and installed the following to get started:

GQXR - An open-source SDR receiver. GQRX played a crucial role in visualizing and recording the signals received from the RTL SDR. Its intuitive interface allowed me to monitor and analyze the incoming signals effectively.

Gpredict - A satellite tracking software, used to visualize the orbital positions of selected satellites. This software enabled me to precisely determine the satellites' locations and facilitated communication with GQRX for initiating and terminating signal recordings based on their positions.

noaa-apt - A dedicated image decoding software used to decode the recorded signals from GQXR and convert them into images. This tool proved essential in the process of extracting valuable visual information from the captured signals.

After setting up the necessary software tools, we embarked on our first attempt to capture images from NOAA Satellites. We started by tuning an adjustable dipole antenna to approximately 137MHz, which is the broadcast frequency used by these satellites. However, our initial pass was plagued by excessive static and interference, making it difficult to obtain a clear signal.

Recognizing the need to address the weak signal, I decided to enhance our setup by incorporating an LNA (Low Noise Amplifier). This amplifier, powered by a 9V battery, helped boost the signal strength. As a result, we were able to audibly hear and visualize the signal more clearly. Despite this progress, we still faced challenges when it came to decoding the signal into an image, as there was significant noise present.

To tackle this issue, I delved deeper into the matter and discovered a potential solution: the acquisition of a filter, such as the NooElec SAWbird+ NOAA. This filter is specifically designed to improve the reception of NOAA satellite signals. It offers effective noise reduction and signal enhancement, which can greatly improve the quality of the captured images.

Alternatively, I came across another approach that involves building a simple band reject filter. One such example is the "Create a Band Reject Filter using Coax - OPEN STUB VERSION (049a)" method. This involves constructing a homemade filter using coaxial cables to suppress unwanted frequencies and enhance the desired signal. I will be trying this in the future to learn more about antennas and the usage of my Vector Networ Analyzer (VNA)

As I explored these options, I weighed the benefits and costs associated with each solution. The NooElec SAWbird+ NOAA filter offers a more specialized and reliable solution, specifically designed for this purpose. On the other hand, building a band reject filter provides a DIY alternative, which can be a rewarding learning experience and cost-effective approach.

As I delved deeper into the realm of antennas and their resonance properties with the target frequency, I found myself captivated by the intricate workings of these devices. To enhance my understanding, I decided to invest in a budget-friendly VNA (Vector Network Analyzer) to measure the SWR (Standing Wave Ratio) of the antennas I was utilizing. This required more research into radio frequencies and their propagation through space.

During my exploration, I stumbled upon many DIY antenna plans, and among them, I discovered some remarkable designs that could be 3D printed. One particular design that caught my attention was the "Helical Antenna Scaffold Set (v4)", which I printed and constructed. I built and fine-tuned the antenna to resonate precisely at 137MHz, achieving the lowest SWR possible. Through trial and error and more than a few iterations, I have honed my skills in antenna construction, each time seeking to improve performance and efficiency.

In my pursuit of optimal conditions, I plan to venture out to an area with less interference, providing a better environment to attempt image reception from NOAA satellites. The promise of clearer signals has me excited about my next attempts.

 Radio frequencies, antenna design, and related subjects have been a tremendous learning experience. I am eager to find a better way to share these projects. As I consider revising the format of my portfolio to accommodate more comprehensive and timely write-ups, I