Sirio HF Base Antenna

Sirio shortwave base station antenna - main technical characteristics

The category includes one wider-range 1/4 Lambda antenna covering 40-70 MHz and two directional yagi configurations tunable between 50-54 MHz. All three solutions have 50 ohm impedance. The omnidirectional configuration has a 360-degree radiation pattern, while the directional antennas have separately specified H-plane and E-plane beamwidth values.

What frequency range does the Sirio shortwave antenna operate in?

The documented frequency range depends on the antenna design. The 1/4 Lambda base station antenna is specified for 40-70 MHz. The 3-element and 5-element yagi antennas are tunable between 50-54 MHz. When selecting an antenna for a radio communication system, the first step is therefore to verify that the operating frequency falls within the specified range of the selected antenna.

Sirio antenna with 50 ohm impedance

All documented Sirio antenna configurations in the category have an impedance of 50 ohm. This applies equally to the 1/4 Lambda omnidirectional design, the 3-element yagi, and the 5-element yagi. In addition to frequency range, the 50 ohm impedance can therefore be directly compared with the technical requirements of the connected radio equipment.

Omnidirectional or directional antenna - which designs are available?

The category includes two different radiation concepts. The 40-70 MHz 1/4 Lambda antenna has a 360-degree omnidirectional radiation pattern. The 50-54 MHz yagi antennas, by contrast, are directional designs. The 3-element version has a documented H-plane beamwidth of 93 degrees and E-plane beamwidth of 60 degrees. For the 5-element version, these values are 72 and 54 degrees.

Sirio omnidirectional antenna for 40-70 MHz

The 40-70 MHz 1/4 Lambda omnidirectional antenna has a documented gain of 0 dBd, equivalent to 2.15 dBi. Its radiation pattern is 360 degrees. The SWR is specified as maximum 1.2 at 40 MHz, while the maximum power is 1000 W. This technical configuration differs from the directional yagi antennas in the same category.

How do the directional yagi antennas differ?

The 3-element and 5-element shortwave antenna designs are both tunable between 50-54 MHz, but their beamwidth, gain, and front-to-back ratio differ. The 3-element version has a gain of 6.4 dBd, equivalent to 8.5 dBi, and a front-to-back ratio of 20 dB. The 5-element version has a gain of 8.4 dBd, equivalent to 10.5 dBi, and a front-to-back ratio of 25 dB.

What antenna gain and maximum power ratings are available?

The documented antenna gain in the category ranges from 0 dBd / 2.15 dBi to 8.4 dBd / 10.5 dBi. The omnidirectional configuration is specified with 0 dBd / 2.15 dBi, the 3-element yagi with 6.4 dBd / 8.5 dBi, and the 5-element yagi with 8.4 dBd / 10.5 dBi. Maximum power is 1000 W for the 1/4 Lambda antenna and 600 W for the directional yagi antennas.

HF antenna and VHF base station antenna - documented electrical data

• 40-70 MHz frequency range for the 1/4 Lambda configuration.
• 50-54 MHz tunable frequency range for the yagi antennas.
• 50 ohm impedance for all documented configurations.
• 0 dBd / 2.15 dBi gain for the omnidirectional configuration.
• 6.4 dBd / 8.5 dBi gain for the 3-element yagi.
• 8.4 dBd / 10.5 dBi gain for the 5-element yagi.
• 1000 W maximum power for the 1/4 Lambda version.
• 600 W maximum power for the 3-element and 5-element yagi versions.

The technical data show that the antennas in the category cannot be treated as a single uniform design. Frequency range, gain, radiation pattern, and maximum power are specific to each antenna construction.

Fixed-mount antenna for radio communication

When selecting a fixed-mount antenna, checking the 50 ohm impedance alone is not sufficient. The 40-70 MHz omnidirectional configuration and the 50-54 MHz tunable directional yagi antennas have different RF characteristics. The operating frequency, radio power, and required radiation pattern should therefore be compared separately with the antenna parameters.

What is the role of the front-to-back ratio in directional antennas?

The front-to-back ratio is documented only for the directional yagi antennas in the category. It is 20 dB for the 3-element design and 25 dB for the 5-element design. The H-plane and E-plane beamwidth values also differ between the two versions, so these parameters can also be compared when selecting between the directional configurations.

What should be checked when selecting a shortwave base station antenna?

We recommend starting the selection of a Sirio shortwave base station antenna by determining the required frequency range. Then check the 50 ohm impedance, omnidirectional or directional design, antenna gain, maximum power, and, for yagi antennas, the front-to-back ratio together with the H-plane and E-plane radiation data.

Sirio base station antenna selection checklist

• 40-70 MHz or 50-54 MHz frequency range.
• 50 ohm antenna impedance.
• 1/4 Lambda or 3-element / 5-element yagi antenna construction.
• 360-degree omnidirectional or directional radiation pattern.
• 0 dBd / 2.15 dBi, 6.4 dBd / 8.5 dBi, or 8.4 dBd / 10.5 dBi gain.
• 600 W or 1000 W maximum power.
• 20 dB or 25 dB front-to-back ratio for yagi configurations.
• H-plane and E-plane beamwidth of the directional antenna.

The antennas in the category differ significantly in construction. For this reason, a single common frequency, gain, power, or radiation value cannot be applied to every version.

FAQ - Sirio shortwave base station antennas

• Which frequency ranges are available?
  The documented ranges are 40-70 MHz and, for the tunable yagi antennas, 50-54 MHz.
• What is the impedance of the antennas?
  All documented configurations have an impedance of 50 ohm.
• Is an omnidirectional antenna available in the category?
  Yes. The 1/4 Lambda design has a 360-degree omnidirectional radiation pattern.
• Which directional antennas are available?
  The category includes 3-element and 5-element yagi designs tunable between 50-54 MHz.
• What gain values are available?
  The documented gain is 0 dBd / 2.15 dBi, 6.4 dBd / 8.5 dBi, or 8.4 dBd / 10.5 dBi.
• What is the maximum power?
  The omnidirectional version is specified for 1000 W, while the two directional yagi configurations are specified for 600 W.

Summary

The Sirio shortwave base station antenna category includes a 40-70 MHz omnidirectional antenna and directional VHF antennas tunable between 50-54 MHz. The documented configurations have 50 ohm impedance, but their gain, radiation pattern, and maximum power differ. To select the appropriate antenna, the frequency range, antenna construction, gain, power, and, for directional versions, the front-to-back ratio and beamwidth values should all be checked.