Transcript
UHXA-406 Helix Antenna
UHXA-406 UHF Helix Antenna
Application & Description Brief Used in point to point communication, the Becker UHF Helix Antenna is made specifically for harsh conditions. The antenna has a high front-to-back ratio. The receiving unit’s physical strength is environmentally and physically rated to the international IP68 ingress protection standards. It is made to interface well with the Becker Electronics UAAC UHF Active Antenna Coupler, especially in tunnel communications (for instance underground mining). It can also act as an End of Line Terminator for tunnel communications. Please refer to the section “Interfacing with UAAC and End Of Line use” for more information about this. An installation example
Functional Features
Technical Features
Interface and extends UAAC usage Sturdy construction Omni-directional Circular Polarized
High gain, high front to back ratio User specifiable frequency from 435MHz to 500MHz Interfaces with Becker Electronics UAAC
Purchase Contact Details Becker Electronics CNR Freda andCR Swart Drive Randburg Johannesburg South Africa 2169
Tel: +27 11 617-6321 Fax: +27 11 908-2275 Website: www.becker-mining.com Email:
[email protected]
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DISCLAIMER All information given in this datasheet is correct to the best of our knowledge, but the company reserves the right to make alterations and amendments to the detailed specification at its discretion.
UHXA-406 Helix Antenna
Performance Specifications Description Nominal Gain VSWR Frequency Polarization H Plane 3dB beam width Front-to-back ratio Rated power Impedance Termination
Spec / Range / Type 10.41 dBd ≤ 1.6:1 435MHz to 500MHz Circular 56.83° > 20 dB 150 Watts 50 Ohms N-Type male
VSWR Radiation Pattern
Mechanical Specifications Descriptor Length (Excluding Mounting Brackets) Height (Excluding Mounting Brackets) Weight
Spec / Range / Type 0.733 m 0.49 m 4.2 kg
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UHXA-406 Helix Antenna
Mechanical Drawing
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UHXA-406 Helix Antenna
Interfacing with UAAC and End Of Line use Interfacing with UAAC The UXHA Helix Antenna interfaces well with the Becker Electronics UAAC UHF Active Antenna Coupler. The UAAC is used with 3 main communication lines. What the UXHA does is that it connects with the UAAC and thus extending the range of the reception on the leaky feeder 3-way line
3 Tunnels without UHXA installation
3Tunnels with Leaky Feeder Cable
3 Tunnels with UHXA installation
Legend description
End of Line use Another important implementation is that the UXHA can act as a Becker Electronics End of Line Terminator. Radiating "leaky" cable systems, in which radio signals are transmitted from a cable rather than from an aerial, can provide two-way radio services in situations where conventional VHF and UHF communications from central areas are not practical. The radiating cable End of Line Terminator is used to prevent unwanted radio frequency reflections presenting themselves within the cable. These unwanted reflections cancel out the wanted signals and radically affect the "throw off the cable". The End of Line unit terminates the radio signal in the characteristic impedance of the radiating cable, but does not present any DC current load to the system. Where the UXHA fits in is that it replaces the End of Line Terminator and thus extending the receiving and sending range of the underground Leaky Feeder System.
Without UHXA installation
With UHXA installation Page 4 of 7
UHXA-406 Helix Antenna
Comparison of Dipole and Helix Antenna Performance
Above graph is an illustration of the RSS (Received Signal Strength) from a dipole antenna versus the RSS strength of an UHXA antenna. The followed methodology is this: Place a RF-signal transmitter rated at 0dBm next to a dipole antenna. Place another dipole antenna 40m away from the first antenna and couple it to a signal strength meter that is put on maximum hold. Iterate the RF-signal frequency between 435.0MHz and 500MHz while plotting the signal strength on the signal strength meter in dBm. Repeat previous steps but use a UXHA Helix Antenna. From the graphs it is apparent that the RSS of the UXHA Helix Antenna is superior to that of the dipole antenna. Also of note is that the RSS of the UXHA Helix Antenna has a far more stable strength with not as much fluctuations as that of the dipole antenna. This makes its behaviour more reliable when applications of multiple frequencies are used.
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UHXA-406 Helix Antenna
Active Tagging RSSI measurements in the underground environment When installed in an underground environment, the Becker Electronics UXHA Helix Antenna has several advantages. The most notable of this is the following: i) Polarization change of signal compensation ii) Close proximity overlap prevention iii) Flat Frequency Response i) Polarization change of signal compensation When UHF radio waves propagate down a mining tunnel, they change their polarization. If you start with a radio wave that is vertically polarized, it will end up as a horizontally polarized radio wave. The rate of change and attenuation depends on a number of factors including: 1. The exact frequency 2. The Height versus Width dimensions of the tunnel 3. The angle of the vertical walls 4. The perturbation in angles of the flat surface (floor) 5. The discontinuities along the surface of the walls, roof and road. 6. The dielectric constant and conductivity of the surfaces – which both affect the reflection coefficient of the radio signal. In practical terms, the detected signal strength do not only depend on the distance but also to a large extend on the polarization distortion (twisting of the tag signal in response to the above listed variables). A circularly polarized receiver antenna does a great deal to normalise the system, delivering a more consistent RSSI vs. Distance readings. ii) Close proximity overlap prevention In cases where antennas are in close proximity to each over (for instance in mining cross-cuts) a significant benefit can be have by focusing the UHXA in opposite approach directions. This helps with the prevention of overlaps. Previous attempts to accomplish this in underground tunnels were unsuccessful due to yagi (and similar in structure) antennas do not retain their directionality very well when installed in tunnels. In contrast, the Becker Electronics UHXA Helix antenna’s response is almost “parabolic”, and as such is equivalent of putting parabolic antennas in the tunnels. The reason why parabolics without a helix structure was not used was because of cumbersomeness due to large diameters needed for directed signal transmission. The Helix thus gives a good compromise between directionality and size. iii) Flat Frequency Response Case studies show that HD-400 dipole antennas give an inconsistent frequency response. This phenomenon can be attributed to the specific frequency tuned nature of the dipole antenna, making it not wideband by nature. The Becker Electronics UHXA Helix Antenna delivers a very flat frequency response over the band, especially when compared to a dipole antenna. In its design and implementation it is a wideband antenna and exhibits a far more predictable gain especially when installed in the complex RF ground plane underground environment.
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UHXA-406 Helix Antenna
Radiation Patterns 3-Dimensional Radiation Pattern
Typical Radiation in the H- plane
Typical Radiation in E-plane
Feed phase angle in the H- plane
Feed phase angle in the E-plane
Ordering Information What’s In The Box
Description
Part No: UHXA-406 – XXXXXX (Base Part No.)
(Serial No)
RX/TX Frequency 435MHz – 500MHz
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UHXA Unit Datasheet Test Results Sheet
