100KHz -30MHz Portable Active Loop Receive Antenna for SDR Radio Receiver

WBL-02 is a portable active loop antenna designed for HF bands for radio receivers. The antenna consists of a pre-amp box and a loop element that made of a copper electric wire with plastic coating. The pre-amp box has two boards, one is the preamp unit, and the other one is the power supply and battery charging. The pre-amp box is powered by 2 cells of 18650 Li-ion batteries in series and a USB-C port is also added for charging the batteries. Moreover, a low-voltage detection feature is also added on the board. When the voltage of the batteries are below the threshold, a led will be on for indication.

The preamp unit is based on the classic LZ1AQ’s circuitry which features with nice frequency flatness response, low distortion and low input impedance. The supplied loop size is 0.64m in diameter with a diameter of 2.1mm copper wire. You can replace the loop wire with a bigger copper conductor, a larger diameter in loop size(longer circumference), 1m or more to achieve a better performance(see notes). The stainless steel wire is not recommended as the loop element for its high resistance velocity. Any copper, aluminum wires, tubes, pipes are fine.

Two SMA ports on the left and right are reserved for the shielded loops, the common shielded loop, the mobius loop, or youloop etc… Currently, this additional feature is added just for the experimental purpose.

 

The pre-amp box can also work with an external bias-T unit. A 12V bias-T is recommended, a bias-T with the voltage higher than 12V is helpless, it adds more current to heat the board, but does not help to the gains, dynamic range and distortion, and the total performance may be degraded or worse. A bias-T with a DC-DC booster or step-down is NOT recommended.

 

Two plastic mounts are installed on the back of pre-amp box. With 2 cable ties, you can mount the box onto a PVC pipe, bamboo rod… The cable ties used here are reusable and releasable, so it is easy and fast to assemble and disassemble our antenna.

 

No other tricks needed to operate this antenna, just hook up the loop element, connect the pre-amp box to your radio with a SMA coax, then slide the switch to ON, that’s all. If the batteries run out (LOW BATT LED ON), just connect it to a USB wall charger with our supplied USB-C cable. It will stop charging when the batteries are full.

 

The WBL-02 can work with any radio receivers with 50ohm or 75ohm input, traditional receivers or new SDR radios.

 

Specification:

• Frequency: 100K-30MHz

• Input Impedance: 3 – 7 ohms

• Output Impedance: 100 ohms

• Loop Wire Diameter: 0.64m

• Loop Wire Material: Plastic Coated Copper Wire

• Wire Conductor Size: 2.1mm in Diameter

• Loop Inductance: 3uH

• Power Supply: 8.4V

• Working Current: 120mA

• Preamp Box Size: 99(L)x66(W)x49(H) mm

 

Features:

• Light-weight and portable, all in a cloth bag

• Just one anenna box, no Bias-T needed

• Powered by 2 x 18650 cells, rechargeable (Not included)
  

• 2 SMA ports reserved for testing different shielded loop elements

• Nice dynamic range, flat frequency response, low distortion, the loop diameter could be from 1m to a large one, like 4m or 5m

 

Package Contents:

• Pre-Amp Box X 1

• Loop Wire X 1

• USB-C Cable X 1

• Releasable Cable Ties X 10

• Additional Cable Tie Mounts for Surplus X 2

• Cloth Bag X 1

Note:

• The antenna box is powered from 2 cells of 18650, they are not supplied in the package.

• You need to prepare a piece of PVC tube for supporting the antenna. A PVC tube with the diameter 20mm is recommended. A 90cm length PVC tube is OK. You can cut the PVC tube into 4 sections with 21 or 22cm for each section, so that it’s easy to organize all of them into a box for portable. When using, connect those sections by 3 pieces of 20mm PVC direct couplings. For the basic kit, the PVC tube is not included, but it is really easy to cut by yourself. See the picture below:

• The performance of this antenna could be variable, and it greatly depends on the size and conductivity of loop elements used, the supplied loop wire is just a compromised solution for traveling purposes. You can’t compare it with the “large” dipoles or end-feds used in ham radio stations.

• The small sized active loop antennas in this kind are mainly used for broadcasting listening. For amateur radio purpose, we strongly recommend to replace the CONDUCTOR of supplied loop wire to a bigger size or use the parallel loops, or a loop of FLAT conductor. At the same time, extend the loop circle’s diameter to at least 1m, 1.5m or more. Rule of the thumb: A loop of low inductance, low load resistance, high antenna current will produce a better frequency flatness, a lower noise floor and a better gain.

• THIS ANTENNA IS ONLY FOR RX ONLY, NOT FOR TX(TRANSMITTING). It could be fully damaged if you deliver more than 500mW RF signal to its RF OUT port.