Satellite Tracking using Gpredict

References General

• Getting started on amateur radio satellites
• The New York Times mocked this scientist in 1920. His discoveries could now take us to Mars

What is Gpredict

Gpredict is an open-source satellite tracking and prediction application. It is designed to help amateur radio operators, astronomers, and satellite enthusiasts track and predict the movements of artificial satellites, including communication satellites, weather satellites, amateur radio satellites, and more.

Here are some key features and functions of Gpredict:

• Satellite Tracking: Gpredict can provide real-time tracking information for thousands of satellites in Earth's orbit. It displays their current positions in the sky, azimuth and elevation angles, and other relevant data.
• Orbit Prediction: Gpredict can predict the future passes of satellites over a specific location. Users can input their geographic coordinates, and the software will calculate when a satellite will be visible and at what azimuth and elevation angles.
• Doppler Shift Calculation: It calculates and displays the Doppler shift for communication with satellites. This is important for radio communication with satellites, as it helps adjust the frequency to maintain a stable connection.
• Ground Station Control: Gpredict can interface with radio equipment to automatically control antennas and radios to track satellites during passes.
• TLE (Two-Line Element) Data: It supports the use of TLE data, which is a standard format for describing the orbits of satellites. Users can update the TLE data to keep track of the latest satellite positions.
• Visual Pass Predictor: Gpredict includes a visual pass predictor that allows users to see on a map when and where a satellite will be visible in the sky, making it useful for planning observations or radio contacts.
• Customization: The application is highly customizable, allowing users to add their own satellites or ground stations, change display settings, and more.
• Integration with Radio Hardware: Gpredict can be integrated with radio hardware and software-defined radios (SDRs) to facilitate satellite communication.

Gpredict is a valuable tool for satellite enthusiasts, amateur radio operators, and anyone interested in tracking and communicating with satellites. Its open-source nature has led to a supportive community and the development of plugins and extensions to enhance its functionality. It is available for various platforms, including Linux, Windows, and macOS.

Install Gpredict

• On Mac install Brew Brew
• Then install Gpredict Gpredict
• On Mac you may also need to install the XQuartz package XQuartz
• To run Gpredict open the Terminal and enter gpredict

How to use Gpredict

• To track satellites you need to create a new module and add satellites to the module.
• Click File > Â New Module
• A new window will open.
• Name the module. In this case Irridium
• Select Base Station
• Create new Base Station. Choose Melbourne from existing list.

• Add satellites to Module by clicking on right pointing arrow.

• When finalised selected satellites will be visible on map.

Python code to extract satellite data from Gpredict

Accessing satellite data from Gpredict using Python can be achieved through Gpredict's Remote Control Protocol (RCP) API. Gpredict provides a simple way to communicate with the software remotely, allowing you to retrieve satellite tracking information and other data. Here are the steps to access satellite data from Gpredict using Python:

• Install Gpredict: First, make sure you have Gpredict installed on your system. You can download and install it from the official website: https://gpredict.oz9aec.net/

• Enable Remote Control in Gpredict:
• Open Gpredict.
• Go to the "Settings" menu.
• Click on "Preferences."
• In the "General" tab, check the "Enable Remote Control" option.
• Configure the "Port" and "Password" settings as needed.
• Install Required Python Libraries: You will need a Python library to communicate with Gpredict over the RCP API. One commonly used library is xmlrpc.client. You can install it using pip:

pip install xmlrpc.client

Python Code to Access Satellite Data: Here's a sample Python code snippet to access satellite data from Gpredict using the Remote Control Protocol (RCP) API:

import xmlrpc.client

# Gpredict RCP server information
gpredict_host = 'localhost'  # Replace with the actual host where Gpredict is running
gpredict_port = 4532         # Replace with the actual port configured in Gpredict
gpredict_password = 'your_password'  # Replace with the actual password

# Connect to Gpredict's RCP server
server = xmlrpc.client.ServerProxy(f"http://{gpredict_host}:{gpredict_port}/rpc")

# Authenticate with the password (if configured)
server.authenticate(gpredict_password)

# Retrieve satellite tracking data for a specific satellite by name
satellite_name = 'ISS'  # Replace with the name of the satellite you're interested in
tracking_data = server.getSatelliteInfo(satellite_name)

# Print the tracking data
print(tracking_data)

# Close the connection
server.quit()

Make sure to replace gpredict_host, gpredict_port, and gpredict_password with your Gpredict server's information. Run the Python Script: Execute the Python script, and it will connect to Gpredict, retrieve the satellite tracking data for the specified satellite, and print it to the console.

This code allows you to access basic satellite tracking data. You can expand on it to perform more advanced operations or integrate it into your projects as needed.

Antenna

• Dual-band Arrow antenna
  • 146/437-10 Solid boom without duplexer.
  • Use two radios with this antenna

• Dual Band Yagi Antenna 2m 70cm VHF UHF Satellite
  • Hand Held Yagi for Satellite Dual Band 2m 70cm
  • SO 239 Connection
  • SWR less than 1.3
  • Power rating less than 60 Watts
  • 145 / 435 MHz
  • Communicate with Radio Satellites, AO-91 AO-92 （Distance of 700km）
  • Gain VHF 10 dB (145 MHz)
  • Gain UHF 15 dB (435 MHz)
  • Boom length 1.28 Metres
  • Weight 700 grams

146/437-10BP Yagi antenna with Split boom without Duplexer

The "146/437-10BP Yagi antenna with a split boom" is a type of Yagi antenna specifically designed for amateur radio satellite communication on the 2-meter (144-148 MHz) and 70-centimeter (430-450 MHz) bands. Here's what the different components of this description mean:

• 146/437-10BP:
  • "146" refers to the 2-meter band frequency range, which covers 144-148 MHz.
  • "437" refers to the 70-centimeter band frequency range, which covers 430-450 MHz.
  • "10" may indicate the number of elements in the antenna, suggesting it's a 10-element Yagi antenna.

• Yagi Antenna: A Yagi antenna is a directional antenna commonly used for satellite communication. It consists of multiple elements, including a driven element, reflector, and director elements. The Yagi antenna is designed to focus its radiation pattern in a specific direction, which is ideal for tracking and communicating with satellites.
• Split Boom: "Split boom" refers to the design of the antenna's boom, the central support structure that holds the antenna elements. In this case, it's "split," meaning it has two separate sections that can be assembled together. This design allows for easier transportation and storage since the antenna can be taken apart and reassembled as needed.
• Without Duplexer: "Without duplexer" means that this Yagi antenna does not include a duplexer as part of the package. A duplexer is a device that allows a single antenna to be used for both transmitting and receiving on different frequencies. In satellite communication, where you often transmit on one frequency and receive on another, a duplexer can be used to manage this, but this antenna does not include one, so you may need to source a suitable duplexer separately if your setup requires it.

Overall, the "146/437-10BP Yagi antenna with split boom without duplexer" is designed for amateur radio satellite communication, specifically on the 2-meter and 70-centimeter bands. Its directional properties make it suitable for tracking and communicating with satellites, and its split boom design allows for easy transport and assembly. However, please note that specific details and features may vary depending on the manufacturer and model of the antenna.

Yagi antenna with or without duplexer

Whether it's better to use a Yagi antenna with or without a duplexer depends on your specific application and requirements. Both configurations have their advantages and trade-offs, and the choice depends on factors like your operating environment, budget, and technical considerations. Let's explore both options:

• Yagi Antenna Without Duplexer:

• • Simplicity: Using a Yagi antenna without a duplexer is straightforward. You connect the antenna directly to your radio, and you manually switch between transmitting and receiving frequencies when working with repeaters or satellite communication.
  • Cost: It may be a more budget-friendly option since you don't need to invest in a duplexer.
  • Flexibility: You can use the Yagi antenna on its own for various purposes, such as directional communication or weak-signal reception.
  • Two Radios: You can use one radio to transmit signals and a second radio to receive transmissions. This avoids the need to have a duplexer or a radio that supports duplex transmission.

• Yagi Antenna With Duplexer:

• • Simplified Operation: A duplexer simplifies the operation when you need to transmit and receive on different frequencies simultaneously, such as when working through a repeater or a satellite. It automates the frequency switching process.
  • Space Efficiency: It allows you to use a single antenna for both transmit and receive purposes, which can be space-efficient, especially in installations with limited space or multiple antennas.
  • Reduced Interference: A duplexer can help prevent interference between the transmit and receive signals, improving the overall performance of your setup.
  • Convenience: For applications like satellite communication, where rapid frequency switching is required, a duplexer streamlines the process and reduces the chances of operator error.
  • Radio with Duplex support: You need to use a radio that supports Duplex.

• Considerations:

• • Cost: Duplexers can add to the cost of your setup. Consider whether the added convenience justifies the expense in your particular case.
  • Isolation: Achieving sufficient isolation between transmit and receive frequencies is critical when using a duplexer to prevent interference. Proper tuning and adjustment may be required.
  • Space: If you have ample space and are not concerned about antenna separation, using two separate Yagi antennas without a duplexer may be practical.

In summary, whether to use a Yagi antenna with or without a duplexer depends on your specific needs and preferences. If you require simultaneous transmit and receive capability on different frequencies, a duplexer simplifies the setup. However, if simplicity and cost are more important, or if you don't require full-duplex operation, a Yagi antenna without a duplexer may suffice. Careful consideration of your operating environment and objectives will help you make the best choice for your particular situation.

Using two radios to transmit and receive an FM signal to the ISS

When communicating with the FM repeater on the International Space Station (ISS) or any other FM repeater in amateur radio, it is common to use two radios—one for transmitting (uplink) and another for receiving (downlink). This setup allows you to effectively work through the repeater and make contacts with the ISS crew or other stations using the repeater.

Here's how the two-radio setup typically works:

• Transmitting Radio (Uplink): The transmitting radio is responsible for sending your signal up to the ISS. You tune this radio to the uplink frequency designated for the repeater on the ISS. For example, the uplink frequency for the ISS FM repeater is commonly around 145.990 MHz.

• Receiving Radio (Downlink): The receiving radio is tuned to the downlink frequency of the repeater on the ISS. The downlink frequency for the ISS FM repeater is typically around 437.800 MHz.

• Full-Duplex Operation: Both radios do not need to be capable of full-duplex operation (i.e. that they can simultaneously transmit and receive on different frequencies). This is because separate radios are used for transmit and receive functions. Full-duplex capability allows you to listen to your own signal and the responses from the ISS or other stations through the repeater.

• Offset and PL Tone: When using a repeater, you typically need to set the appropriate offset (shift in frequency) and PL tone (CTCSS or Continuous Tone-Coded Squelch System) to access and work through the repeater. The offset ensures that your transmit frequency aligns with the repeater's input, while the PL tone is used to activate the repeater.

Here's a simplified step-by-step process for using two radios to communicate via the ISS FM repeater:

• Tune your transmitting radio to the uplink frequency (e.g., 145.990 MHz) and set the correct offset and PL tone.
• Use the transmitting radio to key up and send your signal to the ISS repeater.
• Tune your receiving radio to the downlink frequency (e.g., 437.800 MHz) to listen for responses from the ISS or other stations through the repeater.
• Engage in a conversation while monitoring the downlink frequency on the receiving radio. If no-one is responding to your call (CQCQCQ) then at least you will be able to hear your own voice repeated from the ISS repeater.

This setup allows you to maintain a two-way communication link through the FM repeater on the ISS or other similar satellite repeaters. It's important to follow proper amateur radio etiquette and adhere to the guidelines and procedures for working through satellite repeaters, as they may have specific operational requirements.

What is a Duplexer

A duplexer, when used with an antenna, is a device that allows a single antenna to be shared by both the transmit and receive functions of a radio system. It is commonly used in applications where a single antenna needs to serve both the transmitter and receiver while preventing interference between them. Duplexers are often used in two-way radio systems, such as those used by amateur radio operators, public safety agencies, and mobile communication networks.

Here's how a duplexer works and why it's necessary in certain situations:

• Transmit and Receive Frequencies: In a two-way radio system, there are separate transmit and receive frequencies. When you transmit, the radio transmits signals on one frequency, and when you receive, it listens for signals on another frequency.
• Shared Antenna: In many situations, it is impractical or cost-prohibitive to use separate antennas for transmitting and receiving. Using a single shared antenna is more space-efficient and can simplify the installation.
• Isolation: The challenge with using a shared antenna is that transmitting and receiving signals can interfere with each other. When you transmit, the powerful transmit signal can bleed into the receiver, potentially overwhelming it and causing communication problems.
• Duplexer Function: A duplexer serves as a filter that allows only the transmit frequency to pass from the transmitter to the antenna and only the receive frequency to pass from the antenna to the receiver. It achieves this by using a combination of filters and resonant cavities that selectively pass or block certain frequencies.
• Isolation and Filtering: The key function of the duplexer is to provide high isolation between the transmit and receive paths, ensuring that the transmit signal doesn't interfere with the receiver's sensitivity. This is achieved by attenuating the transmit frequency in the receive path and vice versa.
• Frequency Separation: Effective duplexing depends on having sufficient frequency separation between the transmit and receive frequencies. The duplexer is designed based on the specific frequency separation requirements of the radio system.
• Applications: Duplexers are commonly used in applications like repeater stations, where a station receives signals on one frequency and retransmits them on another. They are also used in mobile and base station setups for various radio communication systems.

In summary, a duplexer is a critical component in radio systems that allows a single antenna to be shared between transmit and receive functions while ensuring isolation between them. It does so by using filters and cavities to separate and filter the transmit and receive frequencies, preventing interference and ensuring reliable communication.

which icom transceivers are capable of full duplex

Several Icom transceivers are capable of full-duplex operation, which means they can transmit and receive simultaneously on different frequencies. These radios are suitable for various advanced amateur radio applications, including satellite communications and certain contesting scenarios. Please note that newer models may have been released since then, and I recommend checking Icom's official website or consulting with an authorized Icom dealer for the most up-to-date information. Here are a few Icom transceivers known for their full-duplex capabilities:

• Icom IC-9700: The IC-9700 is a VHF/UHF all-mode transceiver that covers the 2-meter (144-148 MHz), 70-centimeter (430-450 MHz), and 23-centimeter (1240-1300 MHz) bands. It is designed for satellite and high-frequency operation and features full-duplex capability.
• Icom IC-9100: The IC-9100 is an HF/VHF/UHF transceiver that covers a wide range of amateur radio bands, including HF, 6 meters, 2 meters, and 70 centimeters. It supports full-duplex operation on certain bands.
• Icom IC-820H: While the IC-820H is an older model, it was known for its full-duplex capabilities on the 2-meter and 70-centimeter bands. Keep in mind that this model may not be readily available in the market due to its age.
• Icom IC-970H: The IC-970H is another older model with full-duplex capabilities on the 2-meter and 70-centimeter bands. Like the IC-820H, it may not be readily available in the market today.
• Icom IC-910H: This is another older model with full-duplex capabilities on the 2-meter and 70-centimeter bands. It's worth noting that older models like the IC-910H may be found in the used market.

Remember that full-duplex operation is typically associated with VHF/UHF transceivers designed for satellite communication and certain advanced ham radio activities. When considering a transceiver for full-duplex use, ensure that it meets your specific frequency and band requirements, and consult with knowledgeable hams or experts in the field to determine the best option for your needs.

Solid and Split Booms

In the context of Yagi antennas, the "boom" refers to the horizontal supporting structure to which the antenna's elements (such as dipoles and directors) are attached. The terms "solid boom" and "split boom" refer to two different designs for the boom of a Yagi antenna, and they have distinct characteristics and use cases. Here's how they differ:

• Solid Boom: Continuous Structure: A solid boom is a single, unbroken horizontal structure that runs the length of the antenna. It is usually made of a single piece of metal or non-metallic material.
  • Strength and Durability: Solid booms tend to be stronger and more durable because they are a single piece. They can withstand environmental factors like wind and weather more effectively.
  • Assembly: They are generally easier to assemble since there are no separate boom sections to connect.

• Split Boom:
  • Multiple Sections: A split boom, as the name suggests, consists of multiple separate boom sections that are connected together. These sections can be attached end-to-end to create the complete boom.
  • Portability: Split booms are often used in portable or transportable Yagi antennas because they can be disassembled into smaller pieces for easier transportation.
  • Adjustability: Split booms allow for some degree of adjustability in the overall boom length. This can be useful for tuning the antenna's performance or fitting it into a specific space.
  • Construction: The sections of a split boom are typically attached using connectors, clamps, or other fasteners. The construction and assembly may be a bit more involved compared to a solid boom.

The choice between a solid boom and a split boom for a Yagi antenna depends on your specific application and requirements:

• Solid Boom: Solid booms are often preferred for fixed installations, especially in locations where the antenna will be exposed to harsh environmental conditions. They are also suitable for applications where ease of assembly and installation is essential.
• Split Boom: Split booms are more suitable for portable or temporary setups, where the antenna needs to be transported to different locations or where space for storage and transportation is limited. The adjustability of a split boom can be advantageous when fine-tuning the antenna's performance is necessary.

Ultimately, the choice of boom design should align with your specific needs and the intended use of the Yagi antenna. Both solid and split boom designs can be effective, but their suitability depends on factors such as durability, portability, and ease of assembly.

Transmitting Radio Icom ID-52

• Based on Making ham radio satellite contacts via ISS with the Icom ID-52 and IC-705 radios

The Icom ID-52 is a VHF/UHF Dual-Band Digital Transceiver. It is a portable amateur radio (ham radio) transceiver designed for two-way communication on the 144 MHz and 430 MHz bands and includes various digital voice and data modes. Please note that product specifications and features may have been updated since that time. Here are the key specifications of the Icom ID-52:

General Specifications:

• Frequency Range: The ID-52 typically covers VHF (144-146 MHz) and UHF (430-450 MHz) amateur radio bands. Specific frequency ranges may vary depending on the version and region.

Modes: It supports a wide range of modes, including FM, FM-N (Narrow FM), AM, D-STAR (Digital Smart Technologies for Amateur Radio), and various digital voice and data modes.

• Output Power: The ID-52 provides adjustable output power levels, typically ranging from 5 watts down to lower levels for battery-saving modes.
• GPS: Built-in GPS receiver for location tracking and position reporting.
• MicroSD Card Slot: Allows for the storage of voice and data messages, as well as firmware updates.
• Color Display: Features a color TFT LCD display for easy navigation and information display.
• Water Resistance: The transceiver is typically designed to meet IPX7 water resistance standards, making it suitable for outdoor and field use.

Receiving Radio

• Based on Making ham radio satellite contacts via ISS with the Icom ID-52 and IC-705 radios
• Review - Icom IC-705 Why is this Radio Unique?

The Icom IC-705 is a compact and portable transceiver designed for amateur radio operators. It offers a wide range of features and capabilities, making it a versatile radio for various ham radio activities. Here are some of the key specifications and features of the Icom IC-705:

General Specifications:

• Frequency Coverage: The IC-705 covers various amateur radio bands, including HF (1.8-30 MHz), 6 meters (50-54 MHz), VHF (144-148 MHz), and UHF (430-450 MHz).
• Output Power: The radio provides adjustable output power levels, typically up to 10 watts on HF and 6 meters, and up to 5 watts on VHF/UHF.
• Modes: Supports a wide range of operating modes, including SSB (Single Sideband), CW (Continuous Wave), AM (Amplitude Modulation), FM (Frequency Modulation), and digital modes like RTTY and FT8.
• Integrated Antenna Tuner: Built-in antenna tuner for tuning various types of antennas for optimal SWR and signal matching.
• Battery Operation: Operates on an internal rechargeable battery pack or external power sources. Suitable for portable and field operations.
• Built-in GPS: Includes an integrated GPS receiver, providing location and grid square information for applications like APRS (Automatic Packet Reporting System).
• SDR Architecture: Employs Software-Defined Radio (SDR) technology for signal processing, offering flexibility and adaptability.

Display and User Interface:

• Color Touchscreen: Features a color touchscreen display for intuitive navigation and control.
• Spectrum Scope: Real-time spectrum scope and waterfall display for visualizing signals across the frequency spectrum.
• Multi-Function Knob: A large multi-function knob for easy tuning and menu navigation.
• USB Port: Supports USB connectivity for firmware updates, CAT control, and digital mode operation.

Connectivity:

• Built-in Bluetooth: Allows for wireless connectivity with compatible accessories and devices.
• Wi-Fi Connectivity: Provides connectivity for remote control and operation via mobile apps.
• External Ports: Includes various external ports, such as USB, microSD card slot, and CI-V for control and data connection.

Other Features:

• Voice Recording: Supports voice recording for playback and review of received signals.
• Digital Signal Processing (DSP): Incorporates DSP technology for features like noise reduction, notch filtering, and digital mode decoding.
• D-STAR Capable: Can be used with Icom's D-STAR digital voice and data communication system with an optional module.
• Compact and Lightweight: Designed for portability and field use, making it suitable for activities such as DXpeditions and outdoor ham radio operations.
• Accessories: Compatible with a range of accessories, including external microphones, external speakers, and carrying cases.

These are some of the key specifications and features of the Icom IC-705. It's a versatile radio that combines a wide range of capabilities with portability, making it a popular choice among amateur radio operators for various operating scenarios. Keep in mind that specific details may vary depending on the radio's firmware version and any available optional accessories.

With the Icom IC-705 what is SDR (Software Defined Architecture)

The Icom IC-705 is a portable transceiver that incorporates a Software-Defined Radio (SDR) architecture. SDR is a technology that replaces traditional hardware components in a radio system with software, allowing for a flexible and versatile approach to radio communication. Here's how SDR is used in the IC-705:

• Signal Processing: In an SDR-based radio like the IC-705, the incoming RF (radio frequency) signals are first converted to digital data by an analog-to-digital converter (ADC). This digital data is then processed using software algorithms running on an embedded computer or DSP (Digital Signal Processor).
• Flexibility: The use of software for signal processing makes the radio highly flexible. Different modes (e.g., SSB, CW, FM, digital modes) and frequency bands can be supported through software updates rather than hardware modifications. This flexibility allows the IC-705 to cover a wide range of amateur radio bands and modes.
• Digital Signal Processing: SDR radios like the IC-705 often employ powerful Digital Signal Processing (DSP) techniques to filter, demodulate, and process incoming signals. DSP allows for advanced features like noise reduction, notch filtering, and digital mode decoding.
• Display and Control: The IC-705 features a touchscreen display and user interface that allows you to control various aspects of the radio using software. This makes it easier to access and adjust settings, select operating modes, and view information about your communication.
• Spectrum Scope: SDR radios often include a real-time spectrum scope or waterfall display, which provides a graphical representation of the RF spectrum. This feature allows you to visualize signals across a wide frequency range, making it easier to spot and tune to signals of interest.
• Recording and Playback: SDR radios like the IC-705 can often record received signals as digital data, allowing you to play back and analyze signals later. This is useful for contesting, signal analysis, and troubleshooting.
• Firmware Updates: Manufacturers can release firmware updates to add new features, improve performance, or expand frequency coverage without the need for hardware modifications. Users can update their radios to take advantage of these enhancements.

Overall, the SDR architecture in the IC-705 provides flexibility, adaptability, and advanced signal processing capabilities that enhance the user experience and make it a versatile tool for amateur radio operators. It allows the radio to support a wide range of bands and modes, adapt to changing requirements, and provide features like spectrum visualization and digital signal processing.

Accessories for Icom IC-705

• BNC Plug to SO239 Socket Adaptor Jaycar
• UHF Plug Male PL259 to UHF Socket Female SO239 Right Angle Joiner CB Radio - eBay

Communicating with the FM repeater on the ISS uses two Radios

When communicating with the FM repeater on the International Space Station (ISS) using amateur radio equipment, it is necessary to use one radio to transmit (uplink) and another radio to receive (downlink) for several important reasons:

• Duplex Operation: The FM repeater on the ISS operates in duplex mode, meaning it receives signals on one frequency and simultaneously transmits them on another. This is similar to how terrestrial FM repeaters operate in the amateur radio bands.

• Frequency Separation: To avoid interference between the transmitted and received signals, the uplink and downlink frequencies must be adequately separated. In the case of the ISS, there is a specific frequency pair designated for this purpose.

• Full-Duplex Capability: Many amateur radios are capable of operating in full-duplex mode, meaning they can transmit and receive simultaneously. This capability is essential when communicating through a repeater because it allows you to hear your own transmitted signal and the repeater's response.

• Monitor Your Signal: By using separate radios for uplink and downlink, you can monitor the repeater's output to confirm that your transmitted signal is reaching the repeater successfully. This feedback helps ensure the quality of your communication.

• Adjusting Power and Audio: Having separate radios allows you to independently control the power level of your transmitted signal and the audio volume of the received signal. This control is useful for optimizing communication quality.

• Tracking Satellite Pass: The ISS orbits the Earth approximately every 90 minutes, and the satellite's position relative to your location changes rapidly. Using separate radios for uplink and downlink simplifies the process of tracking the satellite's pass and adjusting your antenna as needed.

• Minimizing Doppler Shift: The ISS's high speed causes a noticeable Doppler shift in the transmitted and received signals. By using separate radios, you can make real-time adjustments to account for this shift, ensuring that your signal stays on the repeater's receive frequency.

• Operational Safety: Having distinct transmit and receive radios helps prevent accidental keying of the transmitter when you intend to listen, which can be disruptive to other users on the repeater.

In summary, using two radios—one for transmitting (uplink) and one for receiving (downlink)—when communicating with the FM repeater on the ISS is necessary to adhere to the repeater's duplex operation, maintain frequency separation, optimize communication quality, and track the satellite's movement effectively. It allows you to operate the station efficiently and make real-time adjustments to account for factors like Doppler shift and satellite pass tracking.

Twisting the Yagi antenna to adjust for polarisation when communicating with the ISS

The Arrow II VHF/UHF dual-band Yagi antenna, like many other directional antennas, needs to be rotated or twisted to adjust for polarization when communicating with the International Space Station (ISS) because the ISS's antennas can have different polarization orientations depending on the satellite's orientation and the specific antennas in use. Proper polarization alignment is essential to maximize signal strength and improve the quality of the communication link between your ground station and the ISS.

Here's why polarization alignment is important and why you may need to twist the Arrow II Yagi antenna:

• Polarization Mismatch: Polarization refers to the orientation of the electromagnetic waves as they propagate through space. In satellite communication, two common polarization types are used: linear polarization (horizontal or vertical) and circular polarization (right-hand or left-hand).

• ISS Antenna Variability: The ISS has a variety of communication antennas onboard, and they may have different polarization orientations. Additionally, the orientation of the ISS itself can change as it orbits the Earth. This means that the polarization of the received signals from the ISS can vary during a pass.

• Maximizing Signal Strength: To ensure you receive the strongest possible signal from the ISS, your ground station's antenna polarization must be aligned with the polarization of the signals coming from the ISS. If the polarization is mismatched, you may experience signal loss or degradation.

• Twisting the Antenna: To achieve the proper polarization alignment, you may need to twist the Arrow II Yagi antenna. This involves adjusting the orientation of the antenna elements so that they are parallel to the polarization of the incoming signals from the ISS. You can determine the correct polarization orientation by monitoring the strength of the received signal and adjusting the antenna until it reaches its maximum.

• Real-Time Adjustment: During a pass of the ISS, you may need to continuously adjust the polarization of your Yagi antenna as the satellite moves across the sky and its orientation changes. This real-time adjustment ensures that you maintain the best possible communication link.

In summary, twisting or rotating the Arrow II VHF/UHF dual-band Yagi antenna to adjust for polarization is necessary because the ISS's antennas and satellite orientation can vary, leading to different polarization orientations of the signals received on the ground. Proper polarization alignment is crucial to optimize signal strength and maintain a reliable communication link with the ISS during its passes overhead. Real-time adjustments may be required to track the changing polarization orientation of the satellite.

LEO Satellite Antenna - 3 Elements for 2 Meters crossed with 7 Elements for 70 cm

A Low Earth Orbit (LEO) satellite antenna with 3 elements for 2 meters (2m) crossed with 7 elements for 70 centimeters (70cm) is commonly used by amateur radio operators for communication with LEO satellites. This type of antenna, often referred to as a "dual-band Yagi" or "crossed Yagi," is designed to cover both the 2m and 70cm amateur radio bands. Here are some key characteristics of such an antenna:

• Frequency Coverage: 2 Meters (2m): This portion of the antenna is designed to operate on the 2m band, which typically covers the frequency range of 144 MHz to 148 MHz in the amateur radio spectrum. 70 Centimeters (70cm): The 70cm portion of the antenna is designed to operate on the 70cm band, which typically covers the frequency range of 420 MHz to 450 MHz in the amateur radio spectrum.

• Number of Elements: 2 Meters: This section of the antenna has 3 elements, typically a driven element, a reflector, and a director. The specific element lengths and spacing are designed for optimal performance on the 2m band. 70 Centimeters: The 70cm section of the antenna has 7 elements, including a driven element, reflectors, and directors. These elements are designed for optimal performance on the 70cm band.

• Crossed Design: These dual-band Yagi antennas often have a crossed design, which means that the 2m and 70cm sections are physically crossed or oriented at right angles to each other. This arrangement allows the antenna to simultaneously receive and transmit on both bands without significant interference.

• Polarization: The polarization of the antenna elements is typically linear. However, the orientation of the elements can be adjusted to match the linear polarization of the LEO satellite you are communicating with. LEO satellites often use circular polarization, so you may need to adjust the antenna's polarization accordingly.

• Gain and Directionality: These antennas are directional and offer gain in the direction they are pointed. The number of elements and their design contribute to the antenna's gain, which helps focus the signal in the desired direction.

• Tracking and Pointing: When communicating with LEO satellites, you'll need to manually track and point the antenna in the direction of the satellite's pass as it moves across the sky. Some operators use tracking software or prediction tools to help with this.

• Mounting and Rotor: To effectively track LEO satellites, these antennas are often mounted on a rotator or antenna rotor that allows you to adjust the azimuth and elevation angles as the satellite passes overhead.

• Coaxial Cable: High-quality coaxial cable is essential to minimize signal loss between the antenna and your transceiver. These antennas are popular among amateur radio satellite enthusiasts because they allow for dual-band operation on the 2m and 70cm bands, enabling communication with LEO satellites that often have downlinks on 70cm and uplinks on 2m.

Proper setup, tracking, and antenna polarization adjustment are critical for successful communication with LEO satellites.

Communicate with the ISS - repeater frequencies - Uplink 145.990 MHz FM Downlink center frequency is 437.800 MHz FM.

Communicating with the International Space Station (ISS) using its FM repeater frequencies, especially for voice contacts, can be an exciting experience for amateur radio operators. To effectively communicate with the ISS using two radios and a Yagi antenna in duplex mode, follow these steps:

Important Note: Ensure that you have the necessary amateur radio license or permissions to operate on these frequencies and follow local regulations.

• Equipment and Setup:

• • Two Radios: You will need two separate radios—one for the uplink (transmitting to the ISS) and another for the downlink (receiving from the ISS). The uplink frequency is 145.990 MHz FM with a 67.0 Hz CTCSS tone, and the downlink center frequency is 437.800 MHz FM (with Doppler correction).
  • Yagi Antenna: Use a directional Yagi antenna that covers the 2-meter (VHF) band (for the uplink) and the 70-centimeter (UHF) band (for the downlink). Ensure that the antenna elements are properly spaced and aligned for both bands.
  • Audio Interface: Connect both radios to an audio interface or splitter. This setup will allow you to hear audio from both radios simultaneously and transmit on the uplink radio while receiving on the downlink radio.
  • CTCSS Configuration: Set the CTCSS tone on the uplink radio to 67.0 Hz. This tone is required to access the ISS repeater. The downlink radio should not use CTCSS.

• Tracking and Timing:
  • Tracking Software: Use satellite tracking software or mobile apps like Gpredict, Heavens-Above, or N2YO to determine when the ISS will pass over your location. These tools can predict passes and provide azimuth and elevation information.
  • Pass Prediction: Identify upcoming ISS passes that are suitable for your location. Focus on passes with higher elevations, as they generally provide better signal quality.

• Communication Procedure:
  • Preparation: Set up your equipment, including the Yagi antenna and tracking software, well in advance of the ISS pass. Be ready to start communication at the scheduled time.
  • Monitoring the Pass: As the ISS comes into view, start monitoring the pass. Listen for other stations that may be using the repeater.
  • Uplink Radio: Use the uplink radio to transmit on 145.990 MHz FM with the 67.0 Hz CTCSS tone. Key your microphone and speak your message. Keep your message concise and clear.
  • Downlink Radio: Use the downlink radio to listen to the ISS's response. Be sure to continuously adjust the downlink radio's frequency to compensate for the Doppler shift as the ISS moves across the sky. You will need to tune slightly above or below 437.800 MHz FM to maintain communication.
  • Recording: Consider recording the pass for reference and to review your communication.
  • Ending the Pass: As the ISS moves out of your range, the communication will naturally come to an end.
  • Politeness and Etiquette: Always follow proper amateur radio etiquette. Be respectful of other operators and prioritize educational contacts when using the ISS repeater.

Remember that successfully communicating with the ISS can be challenging and may require practice. Pay attention to Doppler shift compensation, as it is crucial for maintaining a stable communication link during the pass. Good luck with your ISS communications!

How does the Doppler Effect influence radio communications with the ISS

The Doppler effect, also known as the Doppler shift, is a phenomenon that occurs in radio communication with the International Space Station (ISS) and other moving objects in space. It involves a shift in the frequency of the transmitted signal as the ISS moves relative to the Earth-based station or vice versa. The Doppler effect is important to consider when communicating with the ISS using amateur radio FM (Frequency Modulation).

Here's how the Doppler effect affects amateur radio communication with the ISS:

• Relative Motion: The ISS is in constant motion as it orbits the Earth at a high speed. As a result, there is relative motion between the ISS and an Earth-based amateur radio station during a communication pass.

• Frequency Shift: The Doppler effect causes a shift in the frequency of the radio signal due to this relative motion. The specific direction of the shift (upshift or downshift) depends on whether the ISS is approaching the Earth station or moving away from it.

• Uplink and Downlink Frequencies: To maintain proper communication, the frequencies used for the uplink (transmitting from the Earth station to the ISS) and downlink (receiving signals from the ISS) must be adjusted to account for the Doppler shift. The shift affects both the transmitted signal from the Earth station and the received signal on the ISS.

• Compensation: Amateur radio operators adjust the frequency of their transceivers or software-defined radios (SDRs) in real-time to compensate for the Doppler shift. This ensures that the transmitted signal is received on the ISS at the correct frequency and vice versa.

• Continuous Adjustment: To maintain a stable communication link, operators may need to continuously adjust the frequency of their equipment during the pass as the ISS's relative velocity changes. This real-time adjustment is crucial to prevent signal drift and maintain a clear and reliable connection.

• Proper Tracking: Tracking software, such as prediction programs like Gpredict, can assist operators in predicting the Doppler shift and provide guidance on the required frequency adjustments for both the uplink and downlink. This helps operators stay on the correct frequencies as the ISS passes overhead.

In summary, the Doppler effect in amateur radio communication with the ISS is a frequency shift caused by the relative motion between the ISS and the Earth-based station. Amateur radio operators must compensate for this shift by adjusting their equipment's frequencies in real-time to maintain a stable and accurate communication link. Proper tracking and coordination are essential to ensure successful communication during the pass.

Worm Gear Motors

• Original parts listing Mini Satellite-Antenna Rotator Mk1

• Search ebay for JGY-370 DC12V 0.6 rpm motor
• 0.6-375RPM Metal Gear Motor Low Speed DC 12V/24V Worm Gear Reducer Motor JGY370

• Based on SARCTRAC Production

Motor Driver

• LMD18200T DC Motor Driver Module Speed Regulator Board PWM H-bridgeAU

LMD18200T DC Motor Driver Module is an H-bridge driver component dedicated to the DC motor. Integrated CMOS control circuitry, and DMOS power device on the same chip, the use of which may constitute a complete motion control system with the main processor, motors and incremental encoders. LMD18200 widely used in printers, robots and various automation control.

Features:

• With power indicator, and speed is adjustable.
• Anti-jamming with a continuous flow protection.
• Can individually control a DC motor.
• PWM can help to achieve smooth speed regulation.
• Can achieve turning and reversing.

Specifications:

• Main Chip: LMD18200
• Working Voltage: Control signal DC 4.5-5.5V; drive motor voltage 10-30V
• Maximum Output Current: 3A (instantaneous peak current 6A)
• Maximum Output Power: 75W
• Size: Approx. 55mm x 36mm x 35mm
• Weight: 33g(approx.)

• Schematic from SARCNET Rotator MK1

• Motor Driver available from ebay.

Tracker

LSM303DLHC e-Compass 3 axis Accelerometer and 3 axis Magnetometer Module

References

• SARCTRAC Manual
• Mini Satellite-Antenna Rotator Mk1C
• LSM303 Accelerometer + Compass Breakout

Using the Adafruit 10-DOF IMU Breakout - L3GD20H + LSM303 + BMP180 to control a servo motor to track the ISS

To use the Adafruit 10-DOF IMU (Inertial Measurement Unit) Breakout, which includes the L3GD20H gyroscope, LSM303 accelerometer and magnetometer, and BMP180 barometer, to control a servo motor to track the International Space Station (ISS), you'll need to interface the IMU with a microcontroller like an Arduino or a Raspberry Pi. Here's a general outline of the steps you would need to follow:

Hardware Setup:

• Connect the IMU to the Microcontroller: Wire the Adafruit 10-DOF IMU to your microcontroller using the appropriate connections. You will need to connect the IMU's SDA and SCL pins to the corresponding pins on your microcontroller for I2C communication. Make sure to provide power (VCC) and ground (GND) connections as well.
• Connect the Servo Motor: Connect the servo motor to one of the PWM (Pulse-Width Modulation) pins on your microcontroller. Servo motors typically have three wires: power (usually red), ground (usually brown), and signal (usually orange or yellow). Connect the signal wire to the chosen PWM pin.

Software Setup:

• Install Libraries: Install the necessary libraries for the Adafruit 10-DOF IMU and servo motor control on your microcontroller platform. For Arduino, you can use the Adafruit_Sensor, Adafruit_LSM303, Adafruit_L3GD20_U, Adafruit_BMP085_Unified, and Servo libraries.
• Initialize the IMU: In your code, initialize the IMU by configuring it for the specific sensors you want to use (accelerometer, gyroscope, magnetometer, and barometer). Set appropriate data output rates, measurement ranges, and sensor modes.
• Read Sensor Data: Continuously read sensor data from the IMU. You can obtain orientation and attitude information (roll, pitch, yaw) by processing the accelerometer and gyroscope data. Use the magnetometer for heading (compass) information.
• Calculate ISS Position: You'll need to use external data sources or APIs to obtain the real-time position of the ISS in relation to your location on Earth. Services like NORAD's Two-Line Element Sets (TLEs) provide this information. Calculate the desired orientation of your antenna/servo to point at the ISS.
• Control the Servo: Use the calculated orientation data to control the servo motor. Map the desired orientation to servo angles (PWM values) and send the corresponding control signals to the servo. The servo will adjust its position to point in the direction of the ISS.
• Feedback and Adjustment: Implement a feedback loop that continuously adjusts the servo position based on the real-time sensor data and the desired ISS position. This allows the system to continuously track the ISS as it moves across the sky.
• Testing and Calibration: Test the tracking system and calibrate it for accuracy. You may need to fine-tune the control algorithm and servo response to achieve precise tracking.
• Power Supply: Ensure that you have a stable power supply for both the microcontroller and the servo motor, especially if you're operating the system in a remote location.

Remember that tracking the ISS accurately can be a complex task, and it may require additional sensors or components for azimuth and elevation tracking. Additionally, real-time position data for the ISS is critical for accurate tracking. Continuous monitoring and adjustment are necessary as the ISS moves across the sky.

How to use Gpredict to find out when the ISS will pass over Melbourne

To use Gpredict to work out when the International Space Station (ISS) will pass over Melbourne, you can follow these steps:

• Install and Open Gpredict: First, make sure you have Gpredict installed on your computer. If you haven't installed it yet, you can download it from the official website: https://gpredict.oz9aec.net/. Once installed, open Gpredict.

• Update TLE Data: Gpredict relies on Two-Line Element (TLE) data to track satellites like the ISS. TLE data contains information about the satellite's orbital elements. To ensure you have the latest TLE data for the ISS:
  • Go to the "Satellites" menu.
  • Click on "Update TLE data."
  • Select "ISS" from the list of satellites and update the TLE data.

• Set Your Location: Gpredict needs to know your specific location to predict satellite passes accurately. To set your location:

• • Go to the "Ground Stations" menu.
  • Click on "Add."
  • Enter your geographic coordinates (latitude and longitude) for Melbourne. You can find these coordinates online or use a GPS device to determine them accurately.

• Select the ISS:
  • Go to the "Satellites" menu.
  • Search for "ISS" in the search bar or scroll down to find it in the list of satellites.

• Track the ISS Pass:
  • Select the ISS from the list.
  • Click on "Passes" in the toolbar or right-click on the ISS and select "Predict Passes."
  • A window will open with a list of upcoming passes of the ISS for your location (Melbourne). It will display the date and time (in UTC) when the ISS will be visible, its maximum elevation above the horizon, and the duration of the pass.

• Convert UTC Time to Local Time:
  • Note that the times provided in Gpredict are in Coordinated Universal Time (UTC). You may want to convert these times to your local time zone (e.g., Australian Eastern Standard Time - AEST for Melbourne) for your convenience.

• Plan Your Observation: Once you have the pass information, you can plan your observation accordingly. Pay attention to the maximum elevation, as this indicates how high the ISS will be in the sky during the pass. Higher elevations generally provide better visibility.

• Observe the Pass: On the scheduled date and time, set up your equipment (binoculars or a telescope, if available) and go to a location with a clear view of the sky in the direction of the pass. Be ready to spot the ISS as it crosses the sky.

Remember that the ISS orbits the Earth approximately every 90 minutes, so there are multiple passes each day. Use Gpredict to find the most suitable passes for your observation based on your location and preferences.

What is UTC relative to Melbourne time?

Melbourne, Australia, is typically in the Australian Eastern Standard Time (AEST) zone. However, it's important to note that Melbourne observes daylight saving time (DST) during part of the year, which shifts the time zone by one hour. Here's how UTC (Coordinated Universal Time) relates to Melbourne time:

• Standard Time (AEST - Australian Eastern Standard Time): Melbourne is 10 hours ahead of UTC during Australian Eastern Standard Time (AEST). For example, when it's 12:00 PM (noon) UTC, it's 10:00 PM AEST in Melbourne.

• Daylight Saving Time (AEDT - Australian Eastern Daylight Time): Melbourne observes daylight saving time from the first Sunday in October to the first Sunday in April. During daylight saving time, Melbourne is 11 hours ahead of UTC. For example, when it's 12:00 PM (noon) UTC, it's 11:00 PM AEDT in Melbourne. Keep in mind that daylight saving time rules can change, so it's a good practice to check the current time difference when scheduling events or making plans that involve international time zones. Also, not all states and territories in Australia observe daylight saving time, so the time difference can vary within the country.

• UTC Time can be changed to Local Time in Gpredict by selecting Edit > Preferences > Number formats
• Select Show local time instead of UTC

Data Next Pass for ISS

Polar representation of Satellite Pass Data

A Polar graphical representation for satellite tracking information is a way to visualize and understand the position of a satellite relative to a specific ground station or observer on the Earth's surface. It is a two-dimensional graph that typically represents the satellite's azimuth (horizontal angle) and elevation (vertical angle) relative to the observer's location. This representation is particularly useful for tracking satellites, especially for satellite dish pointing and communication purposes.

Here's how the Polar graphical representation works:

• Azimuth: The azimuth angle represents the compass direction (in degrees) from which the satellite is visible relative to the observer's location. It starts from 0 degrees (North) and goes clockwise around the horizon to 360 degrees, completing a full circle.

• Elevation: The elevation angle represents how high above the horizon the satellite is at a given moment. It is measured in degrees and ranges from 0 degrees (right on the horizon) to 90 degrees (directly overhead). An elevation of 90 degrees means the satellite is directly above the observer.

• Polar Plot: In a Polar graphical representation, a circle or semicircle typically represents the horizon, with 0 degrees (North) at the top (12 o'clock position). The azimuth angles are marked around the circle, with lines extending outward to indicate the direction of the satellite.

• Satellite's Path: To track the satellite's path, you can plot points on the graph showing the satellite's azimuth and elevation at specific times. By connecting these points, you can visualize the satellite's movement across the sky. The path usually follows a curve from the horizon to its highest point (maximum elevation) and then back down to the horizon.

• Real-Time Tracking: Some tracking software or hardware can provide real-time updates of a satellite's position in this Polar graphical format, making it easier for observers to aim their antennas or telescopes accurately.

• Polar graphs are particularly useful for satellite tracking because they provide a clear representation of when and where a satellite will be visible from a specific location. This information is essential for various applications, including amateur radio communication, satellite TV reception, and tracking satellites for scientific observations.

In summary, a Polar graphical representation for satellite tracking information is a visual representation of a satellite's position in the sky relative to an observer's location, with azimuth and elevation angles used to describe its position and movement. It helps users point antennas or telescopes in the right direction to establish communication or observation.

Az/El Satellite Path representation

In the context of satellite observations and tracking, "Az/El" stands for "Azimuth and Elevation." Azimuth and Elevation are two fundamental parameters used to describe the position of a satellite in the sky relative to an observer's location on the Earth's surface. These parameters are crucial for tracking and communicating with satellites, whether for amateur radio, satellite television, or scientific observations.

Here's what Azimuth and Elevation mean in relation to satellite observations:

• Azimuth (Az): Azimuth is the horizontal angle measured clockwise from the North direction. It indicates the compass direction to which a satellite is located when observed from a specific location on the Earth's surface. Azimuth angles typically range from 0 degrees (North) to 360 degrees, forming a full circle around the observer's location. An azimuth angle of 0 degrees points to the North, 90 degrees to the East, 180 degrees to the South, and 270 degrees to the West.

• Elevation (El): Elevation is the vertical angle measured above the horizon. It tells you how high in the sky a satellite is located when observed from a specific location on the Earth. Elevation angles typically range from 0 degrees (right on the horizon) to 90 degrees (directly overhead). An elevation angle of 90 degrees means the satellite is directly overhead, while 0 degrees means it is on the horizon.

Together, Azimuth and Elevation provide a coordinate system that describes where a satellite is located in the sky at any given moment. Observers use this information to point antennas, telescopes, or other tracking equipment accurately toward the satellite. The combination of these angles changes continuously as the satellite moves across the sky due to its orbital motion.

For satellite tracking purposes, you might receive Az/El data or use tracking software that provides real-time updates of a satellite's Azimuth and Elevation angles. This information is vital for tracking and communicating with satellites effectively, ensuring that the equipment is pointed in the right direction to establish a reliable connection or make observations.

References

• Making ham radio satellite contacts via ISS with the Icom ID-52 and IC-705 radios