RECEIVERS AND ANTENNAS

Including Receiving System Accessories

Here's what a user has to say about his AVM receiver...

"At the US Marine Corps Base in Twenty-nine Palms, a desert tortoise (Gopherus agassizii) was apparently trapped in a collapsed burrow. We suspected that the tortoise was deceased. Using our AVM LA12-Q and the low and high attenuator functions, we were able to determine exactly where the transmitter was, certainly to sub-meter accuracy. We carefully dug up the collapsed burrow, expecting to find a dead tortoise. All were surprised to find that the tortoise within the collapsed burrow was alive and well. If the animal didn't have a transmitter applied to it, or if we didn't have use of the attenuator functions, it is almost certain that the tortoise would not have been able to dig itself out."

RADIOTELEMETRY RECEIVERS

The LA12-Q Portable Telemetry Receiver

The LA12-Q is a light-weight, inexpensive radiotelemetry receiver with more high tech features than some of the most expensive receivers on the market. It comes complete with batteries, charger, field use manual and a padded fanny pack.

Compare AVM's LA12-Q Radiotelemetry Receiver!

AVM's LA12-Q Radiotelemetry Receiver	Similarly Priced "Walkie-Talkie" Shaped Receivers
Made in-house specifically for radiotelemetry	Modified commercial communications receiver
Antenna jack seated in heavy duty aluminum	Antenna jack seated in plastic breaks easily
3-position attenuator for precise direction	No attenuators
No AGC, for ease in direction finding	AGC makes direction finding difficult
Temperature controlled oscillator for frequency stability	Non-temperature controlled oscillator creates reception frequency error of 20 kHz in heat
Analog signal strength meter, not LCD display	LCD display doesn't work in cold or at high temperature
Available with up to 10 MHz frequency coverage	Available with maximum 4 MHz frequency coverage
Available from 40 MHz to 230 MHz	Available only from 148 MHz to 174 MHz
Easy enough for a 10-year old to use	49 page operator's manual indicates difficulty

AVM's new LA12-Q Portable Telemetry Receiver is a highly-sensitive, digitally-synthesized VHF radio receiver. It can be tuned to an accuracy of 1 kHz. It is the third generation of AVM's field radio tracking receivers. It combines the light weight of the LA12, the first industry-standard wildlife radiotelemetry receiver commercially produced, with all the high-tech features of the LA12-DS, including digitally-synthesized signal, an analog signal-strength meter, and panel-mounted attenuation... and it sells for about 1/2 the price of the high-end receivers.

Each LA12-Q receiver covers a one (optionally two, four, five or ten) MHz-wide band of frequencies. Frequency selection is done with a 4-segment push-button digital switch. Example: a transmitter at 164.357 MHz is tuned in on the LA12-Q Receiver by entering "4357" into the frequency switches.

Special features that make the LA12-Q Receiver superior to other receivers are:

Continuous frequency coverage allows you to work throughout the entire frequency band without factory-setting of channels or "dead spots."
Lightweight: 750 grams, including batteries.
Visual signal presentation (analog signal-strength panel meter) allows you to "see" your signal before you can hear it. This helps you make better judgements on signal strength than by using audio alone.
Separation of "Gain" and "Volume" Control for clearer signal: this allows you to find and amplify only the signal you want to hear.
Panel-mounted 3-position signal attenuation switch facilitates precision directionality by allowing you to use your directional antenna to walk right up to your transmitter.
Tight signal-rejection window prevents overlap of transmitters close in frequency.
A set of six 1,000 mAh rechargeable NiCad AA Cells and their charger are included.
Padded, zip-top, adjustable-belted, fanny pack carrying case included.

See the picture in the About AVM section for the LA12-Q Receiver pictured in field use.

LA12-Q RECEIVER SPECIFICATIONS

Frequency Coverage	Any 1-, 2-, 4-, 5-, or 10- MHz-wide band, from 40 to 220 MHz
Frequency Channels	None; factory channel setting unnecessary because receiver's frequency coverage is continuous
Signal Presentation	Visual: Analog Signal-strength Panel Meter Audio: Both Speaker and Headphone Jack
Audio Jack	1/4" Standard Phone Jack, Complete with Waterproof Spring-loaded Cap
Frequency Selection	Digital Readout to 0.001 MHz (1 kHz)
Frequency Stability	Better than 300 Hz
Setting Accuracy	Frequency Setting in 1 kHz (0.001 MHz) increments
Volume Control	Separate from Gain Control
Input Attenuation	0 dB, 20 dB and 40 dB Selectable Attenuator Switch on Front Panel
Battery Meter	Switchable Function of Panel Meter, Reads Battery Pack Voltage
Antenna Jack	BNC (bayonet) type
Internal Power	6 rechargeable NiCad AA-cells: 110 VAC, 60 Hz, 60 Hz charger included, Batteries are charged in-place through recharge jack on side of receiver
External Power	Usable through jack on receiver's front panel
Case Size	15 x 15 x 6 cm
Receiver Weight	750 grams, including batteries
Receiver Housing	High-impact Plastic with Heavy-duty aluminum front panel
Warranty	Full 1-year warranty against defects in parts and workmanship

RECEIVER ACCESSORIES

LA12-Q Receiver Power Accessories

Accessories available from AVM to power the LA12-Q Radiotelemetry Receiver:

External 6-cell battery pack with jack compatible with the receiver's external power jack. Power cord is long enough so that this handy little battery pack can be carried and used from the front zipper-compartment of the LA12-Q's fanny pack. This battery pack can be used with either 6 NiMH cells, 6 NiCad AA cells, or 6 alkaline AA cells. Batteries are not included.
DC Adaptor with cigarette lighter jack on one end and jack compatible with the receiver's external power jack on the other end, to directly power the receiver from a vehicle's 12-volt battery.
DC Adaptor with battery clips on one end and jack compatible with the receiver's external power jack on the other end, to directly power the receiver directly from a 12-volt battery.
Fanny Pack Carrying Case is made of black nylon, with zip-top and front zipper pocket, dressed up with the familiar AVM air, land and water animals logo, in white. This case is made specifically for the LA12-Q Receiver with a little room to spare for a notebook and pen. Our new fanny packs' covers zip in both directions so that the antenna cable can exit from one corner when the lid is completely zipped. A fanny pack is included in the purchase price of each receiver.

The Pulse Interval Timer

Temperature transmitter pulse rates may be counted using a stopwatch or AVM's Pulse Interval Timer (PIT) may be used to determine temperatures. The PIT gives a reading of the interval between pulses, expressed in milliseconds. This allows temperature to be determined within the space of two transmitter pulses. Besides being far faster than using a stop-watch to count pulses, readings obtained by the use of a PIT give a higher degree of accuracy and reliability. The PIT is a receiver accessory that receives its input directly from the audio output of any receiver, through the headphone jack.

The PIT has an internal NiMH power supply and is recharged directly through its front panel jack.

The PIT contains the following features:

RECEIVING ANTENNAS

The Forgotten Part of the Radio Tracking System

The selection of receiving antennas is often given very little attention. Yet the proper receiving antennas are often the difference between collection of necessary data and receiving no signal. Raising the altitude of the receiving system is the single most efficient means of increasing signal reception. Selection of the proper receiving antennas can increase signal reception often over threefold.

Antennas available from AVM are:

Hand-held Antennas:
3-element Yagi
3-element Collapsible
M-Yagi Fisheries Antenna
Flexible Lab Whip
Burrow Flexi-Probe
"Fishing Pole" Probe
Handiloop

Replacement Elements:
Yellow-coded (driven elements)
All other color-coded
Boom (3- or 4-element)
Mounting Cross-bracket

Fixed-base or Mobile Antennas:
4-element General Purpose Yagi
7-element General Purpose Yagi
12-element General Purpose Yagi
4-element Null-Peak System
7-element Null-Peak System
12-element Null-Peak System
Omnidirectional Whips:
  Choose a Size:
       1/4-wavelength
       5/8-wavelength
  Choose a Mount:
       Magnetic Mount
       Gutter-clip Mount
       Radial Tower Mount

Antenna Accessories:
Right-Left-Center Switch Box
Null-Peak Switch Box
Cabling, available by the meter
Cable ends, installed
Antenna jack adapters (BNC to UHF; specify existing antenna type)

YAGI ANTENNAS
Yagi-Uda antennas, commonly called Yagis, are the standard directional receiving antennas manufactured and recommended by AVM. Yagi antennas are more directional, i.e., can indicate a more precise direction to the source of a transmitted signal, than any other type of antenna commonly used in radio tracking. AVM's Yagi antennas are optimized for forward gain. Yagi antennas are available in several configurations and sizes.

The most basic Yagi antenna contains a boom, generally about 1 meter in length. Mounted perpendicular to the boom are three elements of similar length: the rear element or reflector, the driven element, and the distal element, the director. The length of the elements and the spacing between the elements are inverse functions of the frequency at which the antennas are designed, i.e., the higher the operating frequency of the tracking system, the smaller the dimensions of the Yagi. The reflector can always be identified as the longest element. The driven element contains the gamma match, which fine-tunes the antenna, and holds the cable connector for attachment to the receiver. One or more directors are used to increase the gain of the antenna.

See AVM's hand-held collapsible Yagi antenna pictured in use in the About AVM section.

Antennas are identified by the number of elements they contain. A 4-element Yagi contains a reflector, a driven element and two directors, while a 12-element Yagi contains a reflector, a driven element and ten directors. The addition of each additional director increases the range over which the antenna can pull in radio signals. As each additional director is added, however, the increase in the gain, is incrementally smaller.

THE NULL PEAK SYSTEM
A Null-Peak System is a matched array of two Yagi antennas, which can be switched either in-phase or out-of-phase to produce, respectively, maximum gain and precise direction to a transmitter. The 4-element Null-Peak System can discriminate to an accuracy of about 1 degree, while the 12-element Null-Peak System is accurate to about 0.5 degree.

John Chenger of Bat Conservation and Management
installs a horizontally polarized 7-element
Null-Peak system on a 7 meter telescoping
mast attached to a tracking van.

The relative distance from which a reference transmitter can be received
using Yagi antennas if all conditions other than the size and number of
antennas are held equal. X equals the range at which a transmitter can be
received using a single, 4-element antenna.

	4-element	12-element
Single Antenna (GP)	X	2X
Null-Peak System (NPS)	1.5 X	3X

The receiver end of all AVM antennas cables is equipped with a BNC (bayonet-type) coaxial cable connector, for attachment to the receiver, while the antenna end of the cable terminates in the sturdier PL259UHF-type connector. If your antenna will be used with LA12-DS Receivers or LA12 receivers made after 1977, please specify this, and both ends of your antenna cables will terminate with UHF connectors, at no additional cost. Adapters from PL259 to BNC are also available, should you wish to use your antenna with several different receivers.

HANDI-LOOP
When short-range directional accuracy is needed in very tight places, our Handi-Loop antenna, measuring only 6 x 10 cm, provides gain and accuracy without the bulk of a Yagi. While the Handi-Loop does not give the range of the Yagi, it is a good compromise when work in difficult, restrictive situations is necessary.

FIXED-MOUNT OMNI'S
Omni-directional or whip antennas detect the presence or absence of signal, but do not indicate its direction. Omni's have less gain than Yagis, but have the advantage of being able to detect signal arriving from any direction. Omni-directional receiving antennas generally have three components:

a Whip Element
a Means of Attachment
a Reflector

AVM offers three forms of the omni. The Mag-Mount Omni consists of the whip and a magnetic base for attachment to the roof of a vehicle. There is no reflector provided, as the metal roof of a vehicle serves as an ideal reflector for the whip.

The Gutter Clip Omni antenna is the simplest omni. It consists of a whip and an attachment clip which is clamped to the gutter, or edge of a vehicle's roof or trunk. Again, the roof or trunk of the vehicle serves as the reflector.

The Tower Mount Omni consists of the whip, a tower-attachment clamp, and four radial reflecting elements, which are mounted at the base of the whip, parallel to the ground, because there is nothing on the top of a tower to serve as the reflector.

Each of the three types of omni's can be provided with a 1/4 or 5/8-wave whip. The 1/4 wave measures approximately 50 cm at 150 MHz and the 5/8-wave whip measures approximately 125 cm at 150 MHz. The 5/8-wave antenna will obtain about double the range over the 1/4-wave whip, but its use isn't always practical because of its size.

All omni's are provided with 3.5 meter cables. Additional cable should be ordered for tower-mount omni's, depending on the height of the tower.

PROBE ANTENNAS

Burrow Probe
Ideal for insertion into burrows, the Burrow Probe is a 2-meter stiff but flexible coax cable with a sensitized end. The probe is still enough to push into a burrow without collapsing, but flexible enough to roll into a 20 cm diameter coil for storage. It enables a researcher to precisely locate dead animals and/or shed transmitters shortening digging out time.

FlexiProbe
A probe similar to the burrow probe, but much lighter weight, is used in a location method commonly referred to as the "Ostfeld fishing pole" method (Ostfeld, 1986). The probe is attached to a long pole, allowing the distal end to dangle from the end of the pole. This allows the researcher to get precise locations on very small animals from paths, without damaging the animals' habitats.

Hybrid Probe
The Hybrid Probe is constructed from the lightweight cable of the FlexiProbe, but its sensitized end is made of the heavier, Burrow Probe Antenna cable. It is designed to be used as a close-up sensing wand.

BENCH WHIP
An inexpensive, flexible, 30 cm whip antenna terminating with an appropriate cable connector for insertion into a receiver's antenna jack is available from AVM for in-lab transmitter testing. The bench whip can also be used for reception in actual studies where only limited range is necessary. For instance, a temperature-monitoring study being done in a laboratory or in a simulated environment may only need this short antenna.

ANTENNA ACCESSORIES

THE NULL-PEAK SWITCH BOX
The Null-Peak Switch Box is a cast aluminum box with two antenna input jacks and one output jack for attachment to a radio receiver. A toggle switch controls whether the antennas in a system are switched in-phase (peak mode) or out-of-phase (null mode). Although a Null-Peak Box is included with the purchase of each null-peak system, boxes can be purchased separately, as replacements or so that general purpose antennas purchased separately can be configured as Null-Peak Systems.

THE RIGHT-LEFT SWITCH BOX
Aerial tracking is generally done by mounting a 4-element General Purpose Antenna on each side of the aircraft. The antennas are pointed roughly 45 degrees from straight ahead and angled downward. The Right-Left Switch Box allows the antenna leads to be plugged into the jacks in the box and a toggle switch allows the user to switch between the antennas, facilitating search on either side of the aircraft.

COAXIAL CABLE ANTENNA LEADS
Standard cabling supplied with all antennas is RG58 A/U. If cables over 15 meters are needed, it is necessary to use a heavier weight of cable (RG-8), because the lighter weight RG 58 will loose too much signal in lengths over 15 meters. Cabling is priced per meter, with an additional fixed price per end-connector, installed.

Because the cost of shipping large amounts of heavy cabling can be prohibitively expensive, we will be happy to advise you on the local purchase of proper cabling, equipped with appropriate connectors.

CABLE CONNECTOR ADAPTERS
There are two types of connectors used in standard radiotelemetry equipment. All AVM's antennas have sturdy UHF-type PL259 Connectors. This connector can be recognized by the threaded barrel and jagged teeth on top of the female connectors, and the loose, threaded collar on the male ends.

AVM's older receivers (all LA11-series, and pre-1974 LA12-series) and AVM's new LA12-Q Receiver, use the lighter-weight BNC connectors. BNC's can be recognized by the two small "ears" on the female portion, and by the diagonal slots on the male portion.

If your telemetry system uses mixed connector types and you wish all antennas to be compatible with all receivers, a small adaptor can be placed on the receiver's antenna connector and the antenna cable can be plugged into the adaptor. Be sure to specify whether the adaptor is to fit a BNC or a UHF Receiver.

REPLACEMENT ELEMENTS
AVM offers a full line of replacement parts for all models of our Yagi antennas. When ordering replacement elements, specify the frequency of the antenna, the model (e.g., 4-element NPS), and the element color code or its position (e.g., green element or second director). Replacement antenna booms, NPS cross booms, mounting brackets and hardware are also available. Note that the gamma match attached to any antenna's driven element is not available separately from the driven element because of tuning requirements.

REFERENCES

Ostfeld, R. S. 1986. Territoriality and mating system of California Voles. J of Animal Ecology 55:691-706.