VHF Receiving Antennas (RA)
Telonics provides a number of different antennas for use in conventional VHF telemetry tracking. There are two basic types of antennas, directional antennas and omnidirectional antennas.
Omnidirectional antennas are designed to receive signals anywhere within a 360 degree radius. These antennas are not used to precisely locate a transmitter but they can be used to recover data or detect presence of a transmitter in a general area. They are often mounted at fixed sites for data collection, or mounted on vehicles (e.g. the RA-5A) to detect transmitters while driving.
To locate a transmitter, a directional antenna is used to obtain a direction or bearing to the transmitter. The bearing is based upon the direction of maximum signal strength. The user can either follow the strongest signal to the transmitter (homing in) or obtain bearings from multiple points and triangulate a location.
When selecting an omnidirectional antenna, users must balance the size of the antenna against its "gain" or signal gathering capability. Bigger antennas provide increased gain, which can allow reception at greater range from the transmitter. Another important consideration is the requirement for "ground plane". Some omnidirectional antennas require a ground plane, which is usually a large metal surface under the antenna. For example, with the RA-5A the ground plane is designed to be the metal roof of a vehicle to which the magnetic base of the antenna is attached. Without a ground plane, the antenna will not perform well and may have an abnormal detection pattern and/or reduced range.
When selecting a directional antenna several factors should be considered. Generally, the more elements an antenna has the higher its gain. However, antennas with more elements are physically larger. Further, when antenna pattern and gain are determined, they are measured in "free-space". If an antenna is not deployed in free-space, its pattern and gain can be impacted. In the case of a directional antenna, that means bearings may be incorrect and/or range reduced from what is theoretically possible.
For hand-held use, Telonics typically recommends our RA-23K directional antenna. These are 2-element antennas that are specifically designed to be held up away from the body. This minimizes impact of the body, ground, and nearby objects on the antenna; and it provides for a bit of additional elevation/height which is always useful when tracking.
Three-element antennas theoretically provide a bit more gain than 2-element ones, but they are also typically more impacted by a user holding them, and thus generally are similar in performance to the RA-23K. Antennas with 5 or more elements are not suited for handheld applications, and are designed to mount on a mast. The mast should support the antenna such that it is separated from all conductive materials (including the earth below and wet vegetation above) by ideally 4 meters minimum in the VHF frequency range.
Antennas with multiple elements ("Yagi" antennas) exhibit a narrower beam width as the number of elements is increased. This narrower beam width is often misinterpreted to mean that antennas with more elements are "more accurate" in terms of the bearing angle. This is not necessarily true. In any case, you bisect the angle over which you hear an equally strong signal to achieve a bearing. To achieve significant improvement in bearing accuracy an RA-NS system (two antennas arrayed together with a null combiner) is a much better choice for obtaining repeatable high accuracy bearings.
To assure performance, all Telonics antennas are assembled, tuned, and tested for the specified center frequency, bandwidth and VSWR characteristics prior to shipment. Telonics antennas are made to the user's specifications and are therefore not returnable, except for manufacturers defect.
If you have any difficulty selecting the proper antenna to meet your study requirements, please contact Telonics.
Models
For applications outside the standard wildlife telemetry bands of 148 to 174 MHz, please consult Telonics.
Unless otherwise specified, antennas are not supplied with coaxial cables. The RA-23K, RA-24K, RA-5A, RA-5B, and RA-10 are supplied with a coaxial cable. Other antennas do not include a coaxial cable and those must be purchased separately.
Telonics specifies gain measured in decibels (dB) relative to a standard dipole (dBd). Some other manufacturers report gain in dBi which results in a higher number. dBi gain equals dBd gain +2.15; thus, 4 dBd gain equals 6.15 dBi gain.
Directional Antennas
| Model | Name/ Description |
Standard Frequency Bands* | Number of Elements |
Antenna Gain | Connections on Antenna | Handheld | Fixed Site | Land Vehicles |
Boats & Ships |
Aircraft |
|---|---|---|---|---|---|---|---|---|---|---|
| RA-1A | paddle (loop) | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
0 | -8 dBd | BNC female Cable not included |
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| RA-23K | flexible "H" type | 142-146 MHz 148-154 MHz 158-162 MHz 162-166 MHz 164-168 MHz 168-174 MHz |
2 | 4 dBd | BNC female RW-2, 5ft. cable included |
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| RA-24K | flexible "H" type | 216-220 MHz | 2 | 4 dBd | BNC female RW-2, 5ft. cable included |
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| RA-3 | Yagi | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
3 | 6 dBd | Supports "pigtail" connection Cable not included |
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| RA-4A | Yagi | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
5 | 9 dBd | Supports "pigtail" connection Cable not included |
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| RA-4B | Yagi | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
8 | 11.8 dBd | Supports "pigtail" connection Cable not included |
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| RA-4C | Yagi | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
14 | 13 dBd | Supports "pigtail" connection Cable not included |
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Note: The RA-24K includes coaxial cable (5 foot) and carrying pouch
*In the chart above, the frequency range is designated as 148-152 MHz, which is defined as 148.000 MHz to 152.000 MHz not 148.000 to 152.999 MHz.
Omni Directional Antennas
| Model | Name/ Description |
Standard Frequency Bands* | Antenna Length |
Antenna Gain | Connections on Antenna | Handheld | Fixed Site | Land Vehicles |
Boats & Ships |
Aircraft |
|---|---|---|---|---|---|---|---|---|---|---|
| RA-5A | 5/8 wave whip with magnetic mount | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz |
46.75 in | 3 dBd | Integral 12 ft. cable with BNC male connector |
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| RA-22 | 5/8 wave whip with magnetic mount | 216-220 MHz 220-225 MHz |
46.75 in | 3 dBd | Integral 12 ft. cable with BNC male connector |
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| RA-5B | 5/8 wave whip | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz 216-220 MHz |
46.75 in | 3 dBd | Integral 17 ft. cable with BNC male connector |
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| RA-6B | stacked collinear | 148-152 MHz 150-154 MHz 159-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz 216-220 MHz |
10 ft | 3 dBd | UHF connection CON-BNC/UHF-J/P adaptor included Cable not included |
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| RA-8 | quarterwave rubber ducky | 7.25 in | -3 dBd | BNC male Cable not included |
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| RA-10 | ground plane independant halfwave | 148-152 MHz 150-154 MHz 158-162 MHz 164-168 MHz 168-172 MHz 170-174 MHz 216-220 MHz |
46.75 in | 0 dBd | Integral 20 ft. cable with BNC male connector |
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| TA-9 | quarterwave Omnidirectional with ground plane | 148-150 MHz 150-152 MHz 164-166 MHz 170-174 MHz 216-221 MHz |
33 in | 0 dBd | Specify BNC female or TNC female for antenna. Cable not included. |
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*In the chart above, the frequency range is designated as 148-152 MHz, which is defined as 148.000 MHz to 152.000 MHz not 148.000 to 152.999 MHz.
Related Products
Legacy Products
This information on discontinued products is provided for individuals who are still using these older systems. Product descriptions may be time sensitive or even outdated. Please contact Telonics if you have questions.
Telonics supports these products as possible based on availability of parts, software, or other considerations; but no longer sells them new.