Broadband Active Antenna
Cross Country Wireless have released a Broadband Active Antenna with a frequency range of 200 kHz to 1400 MHz.
The antenna is a vertical antenna 800mm long with a built-in low noise RF amplifier. A base unit allows 12V power to be fed up the co-axial feeder to the antenna. Common mode RF chokes on all RF inputs and outputs including the antenna output to reduce RF noise when used in a noisy RF environment.
The latest version of the antenna uses a revised antenna element with multiple linear loading to give more gain at higher frequencies especially at 1090 MHz for ADS-B. The new version 3 design uses a 16mm diameter fibre glass tube to reduce wind loading.
Having the antenna amplifier directly connected to the antenna element enhances RF performance as the cable loss between the antenna and receiver doesn't add directly to the overall noise figure at VHF and UHF frequencies. At LF and HF frequencies the antenna acts as an electric field antenna. The antenna can be connected to the base unit with any 50 ohm coaxial cable.
A N type male connector is used on the antenna and a N type female connector is used on the base unit antenna port. A BNC female connector is used for the RF output port on the base unit.
The antenna is useful for airband or aircraft band monitoring as the HF SSB, VHF civil, VHF military and ADS-B frequencies can be monitored using one antenna.
The antenna is in regular batch production.
The Broadband Active Antenna FAQs can be downloaded here .
The Radio User magazine review of the Broadband Active Antenna in the January 2015 edition describing the early version of the antenna can be downloaded here .
Sample of ADS-B reception on 1090 MHz using the Broadband Active Antenna
Recent development of the antenna has resulted in a new broadband antenna element with higher gain at higher frequencies especially at 1090 MHz for ADS-B reception.
The plot shown above was made running RTL1090 software with a RTL-SDR dongle with R820T2 tuner connected directly to the base unit output of a Broadband Active Antenna.
The antenna element was mounted in the clear at 9m above ground level.
The plot shows coverage out to the line of sight range limit. 15m of RG213 cable connected the antenna element to the base unit.
No additional filters were used.
Image showing the RTL1090 table and receiver settings used.
Note the high number of messages received from some aircraft travelling through the coverage area.
Samples of radio reception using the Broadband Active Antenna
A recent post on the Cross Country Wireless Groups.io forum asked if this antenna is suitable for receiving weather satellites if the satellite is directly overhead.
The image is recorded from a NOAA 18 satellite pass on 137.9125 MHz with a maximum elevation of 88 degrees, The noise on the image about one third down shows the null in the antenna pattern from 83 to 90 degrees.
The receiver used for the satellite test was an old Realistic PRO-2006 scanner modified with a 10.7 MHz IF tap so that the signal could be recorded as a RF signal using a SDR-4+ receiver. The recording was then played in HDSDR using FM with a 40 kHz bandwidth and decoded with MultiPSK. Interference on the signal comes from high level radio paging signals on 138.175 MHz overloading the scanner.
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