VHF Receiving Antennas (RA)

Telonics provides several antennas for use in VHF conventional telemetry tracking applications. There are two basic types of antennas, directional antennas and omnidirectional antennas.

Omnidirectional or "Omni" antennas are designed to receive signals anywhere within a 360 degree radius. These antennas are not useful in actually locating the transmitter but they can be used to recover data or simply detect presence or absence of the transmitter in a general area. They are often mounted at fixed sites for data collection or mounted on vehicles for purpose of detecting the transmitters during a search.

For a transmitter to be located it is necessary to utilize a directional antenna and to obtain a bearing to the transmitter based upon the direction of maximum signal strength. Using a directional antenna the researcher can either follow the bearing to the transmitter or obtain multiple bearings to the transmitter from several points and locate the transmitter by a triangulation of the bearings.

In the tables below the antennas are divided into two groups; directional and omnidirectional, based on the usage described above. In selecting an omnidirectioinal antenna, the user must balance the size of the antenna against the "gain" or signal gathering capability. Bigger antennas exhibit increased gain characteristics, translating in this case, to the ability to receive the signal at greater range from the animal. Another important consideration is the requirement for "ground plane". Some omnidirectional antennas require ground plane area, which in this case can be a large metal surface under the antenna. In some cases the requirement for a ground plane area might be fulfilled by the large metal roof of a vehicle under a vertical "whip" antenna mounted in the center of the roof. Without a ground plane, the antenna will not perform well, may not exhibit consistent omnidirectional characteristics and range may be reduced dramatically. Thus the signal being searched for may be missed.

In selecting a directional antenna several factors come into play. The more elements that the antenna has, generally the higher the gain of the antenna. Users should understand that antennas with more elements are physically larger and antennas with 5 or more elements are not very good for handheld applications. The size of the antenna prevents the handheld user from deploying the antenna correctly and though there is more theoretical antenna gain the larger antenna often performs poorly relative to a smaller antenna which can be deployed properly in a handheld application. Larger directional antennas (more elements) must be deployed correctly to perform well. First, they need to be elevated on a mast and be kept away (ideally 4 meters minimum in the VHF frequency range) from all conductive materials (including the earth below and wet vegetation above). An antenna elevated on a mast into the moist leaves of a tree canopy will not perform well. A large directional antenna mounted too close to the metal body of a vehicle will be detuned and the directionality compromised. In addition to more gain, most "Yagi" Antennas (multiple element directional arrays) exhibit a narrower beam width as 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. To achieve significant improvement in bearing accuracy the RA-NS systems (two antennas arrayed together) are a much better choice for obtaining repeatable high accuracy bearings. Individuals looking to achieve high accuracy bearings using these systems may refer to the page describing the RA-NS system, its theory and its practical operation in the field.

Telonics specifies gain measured in decibels (dB) relative to a standard dipole (dBd). The user should be wary when comparing Telonics' specifications for antennas to other manufacturers measured or expressed relative to an isotropic point source (dBi) which may seem superior but, in fact, are not.

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.

As always, if you have any difficulty selecting the proper antenna to meet your study requirements, please contact Telonics. Our engineering staff will be pleased to assist you in the selection of an appropriate antenna.

Details

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, e.g. RW-2, RW-3, RW-5, to connect the antenna and receiver. For RA-2AK, RA-14K, RA-5A, RA-5B, and RA-10, Telonics supplies coaxial cables and BNC connectors. If a longer cable is required, you may purchase the appropriate coupler, e.g. CON-BNC/BNC-J/J, and additional cable separately.

Antenna Accessories
Coaxial Cables
Coaxial Connectors

Models

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
       
RA-2AK "H" type 148-152 MHz
150-154 MHz
158-162 MHz
164-168 MHz
168-172 MHz
170-174 MHz
216-220 MHz
2 4 dBd BNC female
RW-2, 5ft. cable included
RA-23K flexible "H" type 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
       
RA-24K flexible "H" type 216-220 MHz
223-227 MHz
2 4 dBd BNC female
RW-2, 5ft. cable included
       
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
   
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
   
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
       
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
       

Note: The RA-2AK, RA-14K and RA-24K include 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
       
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
       
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
       
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
       
RA-8 quarterwave rubber ducky   7.25 in -3 dBd BNC male
Cable not included
         
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
     
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.
       

*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.

Legacy Products

The information below is provided for individuals who are still deploying these older systems. Some of the system information or limitations, information on frequency allocation or usage, and/or comments made on "state of the art" may be time sensitive or even outdated. Please contact Telonics if you have any questions about the information provided in this section.

Telonics still supports and refurbishes the following products but no longer sells them new: