In this chapter a material list is given for the study of European bats with telemetry. Scroll to subject:
transmitters

antennas

receivers

glue


Radio Transmitters
Technical information
Bats have to be able to fly with a transmitter glued on their back. The maximum carrying capicity of a bat is 5% of its body weight. In this schedule the recommended transmitter weights per bat species.
 
Species Weight female/max weigth transmitter weight male/max weigth transmitter Remarks Manufacturer Researcher
Myotis dasycneme 16-26 gram /0,7 gram 14-22 gram / 0,6 gram 2 stage transmitter Holohil A-J Haarsma
     
     
     
 
Transmitter = 1,5 volt, CW mode, signal with a ‘beep’ interval quicker then one per second (preferably 0,7 per second). Active period depends on battery used (size and capacity of battery). Longevities between 10 to 50 days.
Specifications
One stage transmitter, non amplified. Tend to weight less. Less weight for a given weight of a tag. Relative in-expensive
Two stage transmitter, amplified oscillators. Tend to weight more. Large range for a given weight of a tag. Expensive

Practical information, frequency used
Theoreticaly all frequencys between 30 MhZ and 500 MHz can be used for the study of telemetry. Some frequencies are used for public services and communication and are therefore prohibited. Other frequencies are a known source for interference (high frequency noise). In remote areas, the use of spectrum is usually quite sparse so interference is often not a concern. In urban areas, however, much of the spectrum can be in use. Especially streetlights, car alarms, …can be a nuisance.
As a rule of thump, one can state:
high frequeny have a low ‘’ penetrating’’ power, but further range (suitable in a open landscape)
lower frequencies have a more penetrating power, but less range (suitable for in forest situation, where a signal will be 'absorbed' by trees) and of course the frequency used will have an impact on the longevity of the battery, very high frequencies need more energie to emit. The frequency used has an impact on the type of equipment used (especially on your antennas, because they are adapted to one specific frequency). In the Netherlands for the study of bats, we use 151 or 153 Mhz. This frequency is relatively free of interference and suits for the purpose of tracking bats trough dense vegetation and open areas.
Practical information, activation
A transmitter has a small batterie, which has to be activated just before fieldwork starts. There are two types of transmitters:

Positive Magnetic Shut-off Switches. Characteristics: A magnet is taped to the outside of the transmitter to prevent it from activating. The magnet is removed when the transmitter is deployed and transmission begins. Pros/Cons: Simple activation. Magnets on different collars can sometimes cancel one another out and activate the transmitters. Not suitable for very small transmitters. More expensive than an unfused connection.
Unfused Battery Connection. Characteristics:Unfused connection must be soldered closed to activate transmitter. Connection should then be covered with a protective epoxy. Pros/Cons: Light weight - often used with very small transmitters (e.g., 0.5 g) to keep weight down. Requires practice to activate quickly. Connection leads may break if worried (i.e. if transmitters are exercised during storage). Increased time required for activation; soldering and epoxying can be difficult in the field. Cannot be deactivated if research animals are not successfully captured.


Where to buy?
Check the manufacturer test !
Antenna
Technical information
De size and shape of the antenna used depends on practical carrying comfort nessecary during telemetry study and used frequency. The higher the frequency, the bigger the wavelength and thus the larger the size of the antenna

The size of an antenna is calculated with the following equation:
Wavelength (λ in m) = 300 (speed of light)
Frequency (in Mhz)

Each type of antenna will have a different length:
• omni directional antenna (λ/2)
• x-element Yagi (λ/2)
• loop antenna (λ/6)
an example:
An omnidirectional antenna of 27 Mhz (λ= 11,1) will have the unrealistic size of 5,6 meters. Also the x-element Yagi of this frequency will have elements of about 5,6 meters long. Where as the loop antenna will have a total length of 2 meters, but because it will be bended in a loop with a diametre of 50 centimetres.

On this website you can download an oldfashioned program (GWBASIC) with which you can calculate the size of your antenna.

Type shape Directional Accuracy Distance
• Omnidirectional (dipool) I no only for inaccurate detection 500 m-1 km
• H-adock H yes good 1 km
• X-element Yagi
• yes good- very accurate
• 1-3 km
• Loop yagi
• circel very accurate good- very accurate 500 m- 1 km

Practical information
When buying antenna, make sure it has the correct frequency. Especially when your frequency is not standard, manufactures are known to make mistakes.
For telemetry work with bats, it is important that an antenna has a large gain (is able to hear transmitters a long distance away). An antenna should have at least 6-9 Db gain. A Yagi antenna is a directional antenna, this means the back end (dipool) has a small gain and the front end has a large gain. This is sometimes expressed as the front to back ratio (see figure).

An antenna is very large, thats why shipping cost can be very expensive, especially when buying in America. We advice to buy antenna's in Europe.
Practical information, how to mount an antenna can be found on here.

Where to buy?
Check the manufacturer test !
Receiver
The function of a receiver is to receive the signal picked up by the antenna (to which it is connected by a coaxial cable), amplify it, and make it audible to the user.

Technical information
A receiver is a radio adapted to receive only very high frequencies. Receivers have all kinds of extra’s functions, some of them are useful, others not. For most bat research it is not important to be able to program 100 frequencies. Also a visual signal, in addition to an audible signal, will hardly be a benefit. This is because these visual signals only work with audible signals without interference.

Practical information
Useful options on a receiver are: gain, volume, dail (quick chance between frequencies), noise reducer. Not all receivers have a noise reducer (which amplifies sound and reduces noice). In fact this option is essential to still be able to hear the sound of the receiver in a driving car.
There are two options for an external amplifier:
• an amplifier which works through a car radio. The radio receives the signal of the amplifier and the car audio system will voice the signal. This is a cheap option, but be ware: unfortunately these amplifiers are not so sensitive to high pitch sounds (such as the beep
• an external amplifier between antenna and receiver. This amplifier works as a noise reducer (more information haarsma )
Where to buy?
Check the manufacturer test !
Glue
For the welfare of the bat, one has to use a type of glue which doesn’t become hard and cracky. For example ‘two second glue’ is very aggressive to the skin (leaves burn marks) and it will form a non flexible layer, which will annoy the bat.
There are good biocompatible, waterproof, flexible glues, which can fill in cracks and crevices on uneven surfaces, such as the back of an animal. This flexible glue layer will present a flat surface for the transmitter.

We recommend the following glue’s:
• Smith and Nephew skinbond (from Canada. Howmedca, Guelp). approximately 20 E for a bottle (unfortunately a very impractical bottle in which the glue dries to quickly)
• Sauer haut kleber (from Germany. Manfres Sauer GMBH. Order number = 50.05). approximately 7 E for a tube