The basis for your tracking research begins with the transmitter. As you and an ATS Biologist/Consultant decide which model will best suit your requirement, keep in mind the basic variables you have to work with, once the attachment method has been chosen.

An important consideration in the selection process concerns weight versus battery life. Changes to these variables will effect transmitter operational life . In simplified terms, the bigger the battery, the longer your transmitter will "live". The trade-off is transmitter weight and size. A battery rated at a higher capacity, measured in milliamp-hours, will be larger in dimension and weight, but will last longer.

Another aspect to consider is the pulse rate of the transmitter (the "beep- beep- beep" tone you hear in your headphones), measured in pulses per minute. Different tracking applications require different pulse rates; in general, the faster the pulse rate, the easier it is to track and home-in on an animal. However, a higher pulse rate will reduce transmitter life. The overall design of your study will dictate the total time you will need the transmitters to be operational.

All of our transmitters are pulsed on and off to save power. Most transmitters have the following parts: a battery for power, a control circuit to turn the transmitter on and off, electronic circuitry to generate the frequency and output power, an antenna to couple the signal to the atmosphere, some form of environmental protection and a method to attach the device to the study subject.

As a rule of thumb, for small birds, the total weight of the transmitter should not exceed approximately 3% of the body weight. For fish, the weight should not exceed 2%, and for reptiles and amphibians, 3 to 5%. Remember, additional transmitter program options, like activity and temperature, will reduce the total battery life, since the transmitter is sending more pulses than usual.

 

Most of our transmitter series' have an associated Specification Note. They're available on this site as downloadable PDF files. They include a side and top view outline-drawing of the transmitter and its dimensions, as well as characteristics for the items listed below. Be sure to include this information when specifying transmitters for your study's procurement process.

Transmitter series and model number: Note that there are many series of models for each of the five species classes of transmitters we produce. So, our avian transmitters are all "A" series, our mammal transmitters, "M" series, etc. Next, we group our model numbers by attachment type. A specific model series for birds for instance, is grouped by attachment method, whether backpack, prong and suture, etc.

Technical Specifications
Transmitter Type:	Crystal Controled 2-stage
Calibration Tolerance:	±2.5kHz
Pulse Rate and Width:	Typical on time 20ms, off time 1100ms(controlled by uC)
Frequnecy Stability:	±2.5kHz, -20°C to +40°C
Pulse Rate Variation:	0.01%/volt, ±0.01% for temperatures -20°C to +40°C
Battery:	Lithium
Activiation:	By removing magnet
Encapsulation:	Electrical resin, water-proof, specific gravity; 1.12

Transmitter type: Transmitters can be grouped into several general groups. The first is the method of on/off control. In models using a 1.5 volt battery, an astable circuit is used to control the on off cycle. In models using a battery of 2.5 volts or higher a microprocessor circuit is used to control the on off cycle. Microprocessors normally use a watch crystal to control the timing and are thus very accurate. Astable circuits use resistors and capacitors to control the on off cycle. These components are more variable with changes in temperature and voltage and thus the timing using an astable circuit is less accurate. Astable circuits are used at the low battery voltage because microprocessors normally do not operate below about 2.5 volts.

All transmitters use a quartz crystal to control the transmitting frequency. Transmitters are usually identified by their unique transmission frequency. Most transmit in the range of 30MHz to 230MHz. Since they transmit electromagnetic energy in the radio frequency (RF) range there is no sound for animals to hear. To allow for frequency drift in the transmitter and receiver transmitters should be spaced at least 20 kilohertz (kHz) apart. If spacing is closer than 20 kHz confusion as to transmitter frequency may result. It is also possible to identify transmitters uniquely using ID codes and other means. Call ATS for details.

The electronic circuits of the transmitter can also be varied to increase the output power. At ATS these difference are noted as two stage and three stage circuits.

Calibration tolerance: Describes how close in frequency the transmitter will be to the frequency specified on the order.

Frequency stability: Describes a range of variance for the transmitters actual frequency output within a specified temperature range.

Pulse rate and width: The pulse rate specifies the number of transmission pulses per minute. A rate of 55 pulses per minute (ppm) is ideal for manual homing work. Rates lower than 55ppm increase transmitter longevity, however the direction of arrival of the signal is more difficult to determine and the bearing estimation is less accurate.

Pulse rate variation: Degree of change in the pulse rate due to temperature change and voltage change. This parameter is significant only with astable control circuits.

Battery: Two general battery chemistries are used on ATS transmitters. These are silver oxide and lithium. Silver oxide cells are used on the smaller transmitters and are button shaped. They look like hearing aid batteries. Performance of silver oxide cells is reduced at low temperatures. Their shelf life is limited, about one year, and there is slight current drain when they are not transmitting. Thus transmitters powered by silver oxide batteries should be deployed in the field within 1 to 3 months of delivery.

Lithium batteries are the battery of choice for all transmitters above about three grams in weight. They have excellent weight to power ratio, higher output voltage, good low temperature performance and a rated shelf life of five years.

Activation: in order turn the transmitter on and off, ATS utilizes a reed switch which is encased in the transmitters potting near the outer edge. A small magnet is taped to the outer case of the transmitter which keeps the transmitter "off". By removing the magnet, the reed switch allows current to pass through it, which turns the transmitter "on". Essentially all of ATS transmitters use this method of activation.

Encapsulation: ATS transmitters utilize a water-proof electrical resin, with a specific gravity of 1.12.

You'll notice each ATS Transmitter Spec Note includes a table at the bottom, which looks like this:

                 AVIAN BACKPACK 

MODEL	BATTERY	WARRANTY LIFE (days)						DIMENSIONS         (mm)				WEIGHT (grams)	PRICE GROUP
		BATTERY CAPACITY (days)
		35 ppm*		40 ppm		55 ppm
	3.5V	0.06 mA		0.09 mA		0.12 mA		A	B	C	D
A1310	3PN	121	242	80	160	60	120	18	38	8	11	11	C
A1320	7PN	258	516	172	344	129	258	18	49	8	11	14	C
A1330	16M	553	1116	372	744	279	558	25	61	9	11	32	C

        

Looking at the table above, note that for this transmitter series, the A1300 Avian Backpack, several different specific models are available. They are denoted by the last two numbers: 1310, 1320, etc. What differentiates each model are the battery types used, which in turn will effect the overall dimensions of the transmitter, and of course the weight and operating life of the transmitter. The transmitter's dimensions denoted as "A" "B" "C" and "D" correspond to the letters in the drawing, above.

The battery type used for each model is listed, e.g. 3PN, 7PN, etc. and their associated voltage, along with the accompanying warranty life, in days, and the batteries normal capacity. ATS provides the calculated time the transmitter should be operational, given the current drain during operation. We also list the warranty days for which we guarantee operation; this is equal to one-half the calculated expected life of the transmitter.

An example of various quartz crystals used in transmitters

Notice that transmitter operational life is given for three different pulse rates: 35, 40, and 55 pulses per minute (ppm). We assume a 20 millisecond pulse-width unless otherwise noted. As the pulse rate goes up, the life of the transmitter is diminished. Also listed is the current drain of the battery, in milliamps. This rate of current drain is directly related to the pulse rate of the transmitter. We use this equation to determine battery life: battery capacity in milliamp days / average current drain = Battery Life (capacity) in days.

Miniature circuit boards control transmitter operation

Each model lists an alphabetical price group code, A, B, C etc. All transmitters in a particular price group are offered at the same price, less quantity discounts. Contact an ATS specialist for pricing information.

Examples of lithium and silver oxide batteries

Finally, exceptions and footnotes to the data are listed at the bottom of the sheet. Please contact ATS for assistance in choosing a transmitter for your research application.

Copyright © 2005 Advanced Telemetry Systems, Inc.