Sirio Car and Truck UHF Mobile Antenna

Sirio UHF vehicle antenna frequency ranges and technical characteristics

The range includes 1/4 lambda + 1/2 lambda colinear, 2 x 5/8 lambda radialless and low-profile designs. Documented gain values are 3.5 dB compared with a 1/4 lambda whip, 5 dB compared with a 1/4 lambda whip, and 2 dBi at resonance frequency. H-plane radiation is omnidirectional through 360 degrees.

How do the UHF mobile antenna designs differ?

Physical dimensions and installation methods vary by design. Whip versions are approximately 760 or 990 mm high, while the low-profile version is approximately 36 mm high and 183 mm in diameter. The latter is documented for buses, trains, trams and ceiling mounting.

Vehicle antenna connection and mounting options

Depending on the design, the antenna connection is UHF male PL259 or BNC male on a 1 m RG58 C/U cable. Certain versions support through-hole or magnetic mounting. Magnetic mounts are available with 92 or 127 mm diameter bases, RG58 C/U cable and FME connections. The low-profile antenna uses multi-point screw mounting.

How is the antenna mounted?

A through-hole mount with a 16 mm mounting hole is documented. The mounting template for the low-profile design specifies six 4.5 mm holes and two 16.0 mm holes. Installation uses six M4x30 screws, washers, locking washers and nuts. A 2 mm layer of non-hardening sealing compound is applied to the specified base area.

UHF antenna tuning and SWR adjustment

Tuning depends on antenna construction. One version is adjusted between 375 and 480 MHz by cutting the radiator, with final adjustment performed using an SWR meter. Another design allows the centre frequency to be changed by moving the whip inward or outward. The resonance frequency of the low-profile antenna is adjusted with a tuning screw.

What SWR values are specified for Sirio antennas?

Documented values vary by design. Values include SWR not exceeding 1.6 at resonance frequency and a typical SWR not exceeding 1.5. Another version operates between 429 and 440 MHz with SWR <= 2. For one design, SWR <= 2 bandwidth is at least 30 MHz at 375 MHz, while another specifies a typical bandwidth of 2.5 percent of the centre frequency.

Mobile radio antenna materials and mechanical construction

Documented materials include 17/7 PH stainless steel, nylon, chrome-plated brass, rubber, UV-stabilized ABS, aluminium, brass and steel. Certain versions use a Teflon insulator, gold-plated centre contact and silicone rubber seal. One whip antenna can be tilted through 90 degrees without a key or special tool.

What operating conditions should be considered?

The low-profile version requires a metal ground plane or metal vehicle roof for optimum operating conditions. Its operating temperature range is -40 C to +80 C, and its radome is waterproof. We recommend checking operating frequency, available installation space, connector type, mounting method and tuning procedure before selecting an antenna.

Frequently asked questions about Sirio UHF vehicle antennas

• What frequency ranges are available?
  The category includes versions tunable from 375-480 MHz, operating from 429-440 MHz, and tunable from 420-470 MHz.
• What is the maximum power rating?
  The documented maximum power rating is 100 W.
• What impedance do the antennas use?
  The antennas in this category have an impedance of 50 ohm.
• Is SWR measurement required for tuning?
  Several documented tuning procedures require SWR measurement.

Summary of the Sirio UHF vehicle antenna range

The category covers UHF vehicle antennas with different frequency ranges, gain values, dimensions and mounting methods. We recommend checking the required operating frequency, available mounting space, connector type and tuning method when selecting the appropriate antenna.