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Cross Country Wireless Loop Antenna Amplifier + and VLF Loop Antenna Amplifier

Test loop

The Loop Antenna Amplifier + contains all the electronics needed for home DIY construction of an active loop (magnetic loop) low noise receiving antenna.

The amplifier consists of two units, a weatherproofed outdoor unit for connection to a suitable loop and a base unit to further amplify the signal and 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 indoor unit is a PCB with two BNC connectors and a USB socket to take 5V from a USB socket on a PC or phone charger.

Like our other active antenna products it has RF overload protection to allow it to be used very close to transmit antennas without damaging the amplifier or the attached receiver.

The loop depends on what the user has available. We have tested it with simple wire loops or deltas, coax loops and an alloy loop made from a bicycle wheel rim. We supply a 3m (10 ft) length of wire as a simple loop to make a first loop for testing.

The photograph on the right shows the prototype with a 1m diameter loop of LDF4-50 coax cable as a test loop.

With a simple wire loop or delta and a small USB powerbank it makes a very compact and portable receiving antenna for holiday listening or covert use.

The latest + version can now have the head unit powered directly from receivers with a 5V or 12V bias-tee such as the SDRplay receivers or some RTL-SDR dongle receivers with a bias-tee option. The head unit also has reverse polarity protection in case of an incorrect bias-tee connection.

We also make a VLF version of the Loop Antenna Amplifier. This uses a DC coupled amplifier design with a very low input impedance to match a small loop (around 1 m diameter) in the ELF, VLF and LF bands. The head unit with a bias tee unit covers from 500 Hz to 1.6 MHz making it ideal for ELF and VLF research, NDB beacon monitoring and long wave and medium wave DXing.


Loop Antenna Amplifier + US/international shipping
Loop Antenna Amplifier + with UK/EU shipping

The PayPal button automatically adds 20% VAT during the transaction if the buyer is in the UK or EU.

Bias tee

We can also supply a 5 to 15V Bias Tee based on our Loop Antenna Amplifier base unit PCB

There is no additional amplifier and the DC input from the 2.1 mm DC socket is filtered before being coupled to the antenna socket.

It also has reverse polarity protection to protect the antenna amplifiers coupled to it.

The maximum DC current through the bias tee is 1A so it can be used to supply power to up to 10 High Z Antenna Amplifiers or 10 Loop Antenna Amplifiers in a phased array as long as there is a DC circuit through the phasing coax and switching arrangements.

Bias Tee PCB with US/international shipping

Bias Tee PCB with UK/EU shipping

The PayPal button automatically adds 20% VAT during the transaction if the buyer is in the UK or EU.

We can also supply a RF quiet 12V 2A power supply to power the bias tee PCB and amplifiers.

The Loop Antenna Amplifier is to be reviewed in the March and April issues of Radio User magazine.
Here is a link to the preview web page.

Here's a video of the prototype of the Loop Antenna Amplifier in use with a loop made out of a 700C bicycle wheel rim. The video is made during a field test in a very quiet rural environment. Watch the volume control during the early few seconds of the video due to wind noise on the camera phone used. It clears up later.

Contact Chris Moulding via

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