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Antennas, Cables, and Dongles

When ordering antennas and cables, it is important to ensure:

 

  1. Connectors between the coaxial cable, antennas, and receiver are compatible.
  2. The impedance rating of all cables, connectors, and dongles are the same (50 Ohms).
  3. Cable type is suitable for the length needed.
  4. Get recommended equipment if inexperienced with the technology (highlighted in green).

 

Select an item from the list below to learn more:

Antenna Types

A variety of antenna options exist for VHF telemetry. To date, users have used 3, 5, 6, and 9-element Yagi directional antennas, and single-pole omni-directional antennas. The 9-element Yagis have a long, narrow detection range, whereas 3, 5, or 6-element Yagis have a gradually shorter and wider detection ranges. Omni-directional antennas are best suited for determining species presence-absence patterns (e.g. seabirds at a colony), or for detecting birds in close proximity to stations (within a few hundred metres), but not for providing directional information (e.g. departure directions of songbirds from a stopover site).

When ordering antennas, it’s important to know what frequency you need it to be tuned to. For detecting Lotek tags, antennas must be tuned to 150.1 MHz, 151.5 MHz, or 166.380 MHz, depending on region. For detecting CTT tags, antennas must be tuned to 434 MHz.

Antennas can be purchased from the following suppliers:

Use the table below to help select your antenna:

Antenna type Typical price (USD) Impedence Theoretical range Radiation pattern
3-element Yagi $$$ 50 Ohms ~5 km Wide directional
5-element Yagi $$$ 50 Ohms ~8 km Directional
6-element Yagi $$$ 50 Ohms ~10 km Directional
Items listed in green are recommended.

‘Local’ monitoring station with 5′-element antenna

Coax Cables

Cable type Typical price (USD) Impedence Max attenuation
(dB/100 ft)
Suggested length
RG-58 < 100 ft. @ $0.83/ft. 53.5 Ohms 4.4 @ 100 MHz

6.0 @ 200 MHz

8.5 @ 400 MHz

< 50 ft./15 m
RG-213 < 100 ft. @ $1.79/ft. 50 Ohms 2.3 @ 100 MHz

4.8 @ 400 MHz

< 100 ft./30 m
Items listed in green are recommended.

A helpful guide on coaxial cables can be found on the Wilson Amplifiers website

A catalogue of cables and their specifications can be found on Allied Wire & Cable.

RG58 – basic communications cable that typically come with a BNC connectors. Best used for lengths less than 50′. The least expensive option.

RG213 – higher grade cable that can be used at length of up to 100′ with low signal loss. Custom cable ends depending on distributor/manufaturer. Moderate price.

TWS/LMR-400 – similar to the RG-213, but higher quality (stronger weather/sun resistance) coating. Best for longer-term installations and long cable length. Most expensive. Manufacture can suggest which cable is best for your needs – LMR is generally more affordable.

Radio Dongles

Radio dongles, also known as SDR’s, are the devices that convert the analog signal received by the antennas into a digital signal that can be interpreted by the SensorGnome or SensorStation. Note that Lotek receivers have a built-in converter and do not require these for station operation. Note that SensorStations only need an SDR for antennas tuned for Lotek tags (anything that isn’t 434 MHz).

While there are dozens of available SDR’s on the market, only four models are compatible with Sensorgnomes and SensorStations. Most commonly used are the FUNcube Pro Plus which have the smallest signal-to-noise ratio (SNR), noise figure, and DC voltage spike (poor reception at nominal frequency), and power rating. However, FUNcube dongles are the most expensive, costing ~$200 USD, compared to $35 USD for the RTL-SDR. See the table below for more information:

Receiver Price (USD) Power in use Power while idle Reliability Typical noise figure
RTL-SDR blog V3 $22 1.5 W 0.7 W Unknown ~5 dB @ 144.3 MHz
NESDR SMArt v4 $24 1.54 W <0.25 W Unknown Unknown
NESDR SMArtee $26 1.43 W Unknown Unknown Unknown
NESDR Smart XTR $38 1 W 0.6 W Unknown Unknown
* CTT dongles listen to 434 MHz and are only used to make Sensorgnomes compatible with CTT tags.

Items listed in green are recommended.

Connectors

There are several types of connectors that are used with radio antennas and coaxial cables, but not all are made the same. Therefore, it’s important to know what kind of connectors your antennas have and which are most suitable for a Motus station.

There are four connector types commonly found in Motus station setups: UHF (PL-259); N-type; BNC; and SMA.

Most 9-element Yagis and omni-directional antennas tend to come with a female UHF or N-type connector, but this should be verified prior to purchase. Three and 5-element Yagi’s usually come with a male BNC connector and so they can be connected to a Lotek SRX receiver directly, or to a FUNcube with female BNC to male SMA adapter.

As mentioned above, it’s important to keep the number of connections to a minimum to reduce the amount of signal loss and introduced noise.

The following table outlines where we typically see these connectors. Dongles are the analog-to-digital converters that are part of the Sensorgnome (typically we use FUNcube dongles, or FCD).

Antenna Cables Dongles Water resistance
UHF Typical Common Never Good
BNC Some Lotek Common Never Poor
Items listed in green are recommended.

The following are some common uses of these connectors:

  1. Coax cable with male BNC connector at one end and male UHF connector at the other end (for Lotek receivers or Sensorgnomes with female BNC to male SMA adapter).
  2. Coax cable with a male BNC connector at both ends with a BNC female to UHF male adapter (Lotek receivers or Sensorgnomes with female BNC to male SMA adapter).
  3. Coax cable with custom female UHF connector at the antenna end and a male SMA connector at the FUNcube end. (Option with fewest adapters and therefore less signal loss, but may be more expensive due to custom ends). Sensorgnome only.
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