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A circularly polarized quadrifilar helix antenna (QHA) is an excellent choice for satellite communications, especially for VHF/UHF bands commonly used for satellite repeaters, as its circular polarization matches the polarization of many satellites. However, using a QHA for the 10-meter band is less common due to the large physical size and less frequent use of 10 meters for satellite communication.

For the 10-meter band, you might consider these alternatives:

Directional Yagi-Uda Antenna: Offers high gain and can be used for both satellite uplinks and downlinks. A rotator is usually required for tracking.

Helical Antenna: Circularly polarized and can be adapted for 10 meters, but its size and build complexity are significant for this wavelength.

Crossed Dipole (Turnstile) Antenna: Relatively simple to build, supports circular polarization, and is effective for satellites.

Log-Periodic Antenna: Provides broad frequency coverage and can work for 10 meters and higher bands.

Key considerations:

Polarization: Circular polarization (CP) reduces fading caused by polarization mismatches, ideal for satellite use.
Tracking: Depending on the satellite's orbit, you may need an antenna with elevation and azimuth tracking.
Frequency: Ensure the antenna design is optimized for the uplink and downlink frequencies of the satellite you plan to use.
If your satellite work focuses primarily on 10 meters, investigate the specific satellites and their requirements to choose an antenna that balances gain, beamwidth, and polarization needs.
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Need two Antennas for Sat systems:

separate antennas for uplink and downlink is a common and practical approach for satellite repeater communication, especially if the uplink and downlink operate on different frequency bands (e.g., 10 meters for uplink and VHF/UHF for downlink). Here's why:

Benefits of Separate Antennas:
Frequency Optimization: Each antenna can be optimized for its respective band, ensuring better performance.

Uplink: Typically requires a directional or high-gain antenna for efficient power transfer.
Downlink: Often needs a sensitive and well-matched antenna to receive weaker signals from the satellite.
Isolation: Using separate antennas reduces the risk of interference between the transmitted signal (uplink) and the received signal (downlink).

Flexibility: It allows for independent adjustment of each antenna's polarization, orientation, and gain characteristics based on the satellite's requirements.

Practical Setup:
Uplink Antenna: A Yagi or helical antenna for 10 meters with high gain to ensure your 50-watt transmitter efficiently reaches the satellite.
Downlink Antenna: A circularly polarized or omnidirectional antenna (like a quadrifilar helix or crossed dipole) for the VHF/UHF band to effectively receive signals from the satellite.
If tracking is required, you can mount both antennas on a rotatable setup to follow the satellite's movement. Alternatively, an omnidirectional downlink antenna might suffice for satellites with strong signals and low-altitude orbits.