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

ICOM IC-7300 – SDR radio in a box

Finally the new IC-7300 arrived, and I am still in the process to get familiar with it. I could not resist, as my IC-718, though reliable, is quite “outdated” in its technology, developed more than a decade ago.

Unfortunately, the first IC-7300 unit I picked up from the retailer in Singapore, had a DOA (defect on arrival): the CW keyer always sending dashes. Luckily, there was a second unit available, and it was exchanged without any problems.

Now the new unit is in operation for a week and doing its job without any problems. Size and weight are the same as my IC-718, but the features are not comparable, and it is a real advance in technology. The menus are intuitive and signal reception is excellent, as I can adjust all parameters – gain, filter bandwidth and response, audio processing etc. – according to the actual band conditions.

IC-7300

Two days ago, I setup the configuration for digital modes, connecting my Apple MacBook via USB, using fldigi and the IC-7300 built-in USB sound interface and serial control. So there is no need for any additional interface box, just one USB connection between computer and radio. It works fine, and I was able to make my first contacts in PSK-31.