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Tag: active loop

LZ1AQ Active Loop Antenna

After many years using an active loop antenna with the Cross Country Wireless Loop antenna amplifier for my SDR, I upgraded to the LZ1AQ active loop amplifier AAC-1C.

I replaced the former single loop wire – made of stainless steel – with two parallel loops using AWG10 (2.6 mm) copper wire. The loop diameter is 70 cm and the distance between both loops is 44.5 mm.

clamps for amplifier box
end cap small
end cap large
loop holder
all parts mounted
LZ1AQ amplifier board

As a holder I use a 1600 x 35.5 mm PVC tube (marked as 32 mm UPVC pipe) and added a 710 x 21.5 mm PVC tube (marked as 15 mm UPVC pipe) to support the loop. All additional parts are 3D printed in PETG. Besides the end caps and loop holder the wires are additional supported using four spreaders.

As before, the loop is mounted horizontal outside the apartment window in the 17th floor. In connection with my SDR the usable frequency range is 20 kHz to 55 MHz.

3D printed parts (stl)Download

SDR with Active Antennas for HF

A couple of weeks ago I started to gather my first experiences with software defined radios (SDR) and active antennas. I started with low investment, using the RTL SDR dongle, but I quickly realized that using the direct sampling mode for HF is not an ideal solution and added the Spyverter HF up-converter.

For my first trials I used a Mini Whip from RA0SMS as antenna, but the results were quite disappointing.

mini-whip

Finally, I ended up with an active loop antenna (see featured image), using the Cross-country Wireless Loop antenna pre-amplifier (10 kHz to 30 MHz version). The pre-amplifier is powered with 13.8 V via a bias-tee. Common mode chokes on the antenna line and all power lines helped to reduce noise, especially on the low bands. This is final hardware setup setup:

The setup is now running 24/7 on a Raspberry Pi 3B+ using GQRX and WSJT-X. I was surprised, how many stations and countries can be decoded down to 80 and 160 m.

PSK-80m

Further Information

Talk given during SARTS monthly meeting

PSK reporter link to stations currently received by 9V1KG