Details

Our crossed dipole antenna KX-137 offers best conditions for an optimal reception of the polar orbiting weather satellites in the 137 MHz range.

Construction and Function:

Two horizontally mounted crossed dipoles are coupled through a phase shifting network so that true circular right hand polarized reception is achieved. For signals arriving parallel to the surface this arrangement acts as an omnidirectional linearly polarized antenna. With increasing elevation angle we get an increasing vertical radiation component and the polarization changes from linear over elliptic into circular. Thus the up-looking KX-137 is the ideal counterpart to the downlooking satellite antenna and always gets the maximum possible radiation energy.

A very low-noise preamplifier with a high-Q-filter is integrated inside the antenna head. In that way, the KX-137 avoids the performance-degrading cable- and matching losses that are always present in other configurations and effectively suppresses interference from strong neighborhood-stations like aviation or ham-radio. A passive reflector amplifies reception from the satellites above and reduces fading caused by surface reflections.

To enable the KX-137 to unfold its full performance, it should be mounted so that there always is an open line of sight to the satellites. Then noise-free images in a range of about 5000 km can be expected.

Technical Data

• Wide vertical reception angle allows reception from horizon to horizon.
• Reflector elements suppress surface reflections.
• Righthand circular polarisation.
• Internal low-noise preamplifier with typ. 17 dB gain.
• High selectivity due to high-Q-filter in the 137 MHz range.
• N-type connector 50 Ohms.
• 9 V to 15 V DC supply through the coaxial cable.
• Dimensions: Height: ~100 cm, Width: max. 115 cm.
• Mastmount, max. 60 mm diameter.
• Weight: ~ 1 kg.

Designed for Onboard Use

In most cases, regular full-size satellite antennas are too large and too weather-sensitive for onboard operation. The MX-137, however, being especially designed for this, measures only about half the size due to its flexible and very sturdy elements. All sensitive electronic components are contained in a water- and UV-resistant sturdy box. The mast mount is made of stainless steel only and the N-type connector is watertight. In an urban environment the model KX-137 should be preferred: It reduces possible reflections from buildings or walls.

Technical Data

• Wide vertical reception angle allows reception from horizon to horizon.
• Internal low-noise preamplifier with typ. 17 dB gain.
• High selectivity due to high-Q-filter in the 137 MHz range.
• N-type connector 50 Ohms.
• 9 V to 15 V DC supply through the coaxial cable.
• Maximum size between the ends of the elements: 54 cm.
• Dimensions of antenna-box: 13.5 cm x 7.5 cm x 10.5 cm.
• Stainless steel mastmount, max. 60 mm diameter.
• Weight with mastmount: 0.6 kg.

Built for Passive Antennas

The AA-137 preamplifier not just compensates for cable losses, it improves the noise figure, sensitivity and selectivity, i.e. overall system reception performance. The five high-Q-filters are carefully adjusted on our network analyzer workplace. They create an excellent selectivity against the nearby aviation and ham-radio frequency bands. DC power is automatically fed from the receiver through the coaxial feed line.