The Loop Antenna Amplifier manufactured by Cross Country Wireless model LAA++ V4 (Filtered Version) contains all the electronics needed for home DIY construction of an active loop (magnetic loop) low noise receiving antenna. Sorry, sold out - new stocks expected early March 
The head unit can be used on its own powered by the internal bias tee inside a SDRPlay receiver or any other Receiver that has a +5v DC BiasTee option.

Note:  Although direct +5V BiasTee supply from Radio is supported, there is an increased risk of interference due to significant increase in Inter-modulation distortion. Using the 12V DC BiasTee unit (supplied) will always give better performance!

The amplifier consists of two units: a weatherproofed outdoor head unit for connection to a suitable loop and an optional bias tee unit to provide DC power up the coaxial cable to the outdoor unit.

The outdoor unit is housed in a polycarbonate box with stainless steel antenna connections and a BNC socket. The bias tee unit is a PCB with two BNC connectors and a DC socket to take DC power from a battery or power supply.

The Antenna has RF overload protection to allow it to be used close to transmit antennas without damaging the amplifier or the attached receiver.

The loop depends on what the user has available. The Amplifier head has been tested with simple wire loops or deltas, coax loops and an alloy loop made from a bicycle wheel rim. 

A 2.5m (8 ft) length of wire is supplied as a simple loop to make a first loop for initial testing or even permanent installations.

The Bias Tee unit is intended for use with a +12 V DC feed which allows the head unit amplifier to have a greater dynamic range than with the 5 V DC available from SDRPlay receivers, or other receivers that have a +5V BiasTee option fitted.

The components in the internal bias tee inside a SDRPlay receiver limits the minimum frequency to 500 kHz. Using the optional bias tee unit allows the antenna amplifier to work over its full range. This is ideal for fixed station operations with high quality loops and high performance base station receivers or transceivers.

Specifications CCW LAA++ V4 (filtered version) applicable with 12V DC Power applied with BiasTee unit supplied

• Frequency range (Loop Antenna Amplifier 90 kHz - 55 MHz    (note that coverage down to 90 kHz is possible using the BiasTee unit supplied)                                                  
  

• Output impedance: 50 ohms

• Inter-modulation distortion at 12V DC by using BiasTee unit Supplied:
  OIP2: >+70 dBm 
  OIP3: >+32.5 dBm
  (Note: Distortion is significantly worse when the loop is powered from +5V BiasTee source from Receiver)
  

• Gain (head and base units Loop Antenna Amplifier  25 dB at 14 MHz

• Noise figure: 0.79 dB

• Supply voltage (head unit): 4.5 to 15V from a bias-tee feed via the coaxial cable

• Supply current (head unit fed with 5 V from bias-tee ): 30 mA

• Supply current (head unit fed with 13.8 V from bias-tee): 40 mA

• Loop antenna outdoor unit connectors: Two M6 stainless steel threaded studs and
  BNC female (RF out 50 ohms)

• Loop antenna amplifier bias tee board connections:
  -BNC female (RF input and DC feed to outdoor unit),
  -BNC female (RF output to receiver),
  -DC connector/lead (for 5 -12 V DC power input)    
  

SDR Kits Ltd is an authorized Reseller of the Cross Country Wireless Loop Antenna

Link to an independent Video review of 4 popular Loop Antennas  including the LAA++ (34 min duration)