Re: VLF/LF/MF/HF Active Vertical VLF Performance


Robert, VA3ROM
 

Hi Jim,

Just setup my KiwiSDR to monitor WSPR beacons 24/7 on LF and MF to see how well the receiver works. Picked up two Great Lakes MF WSPR stations but nothing on LF yet. Not too many WSPR stations transmitting LF and MF beacons. Never had a decent antenna for "down under" 80 m before. FT8 signals on 160 m coming in strong even using an RTL-SDR v3 direct sampling SDR so it provides a decent signal to a not so great 8-bit SDR dongle. I'm still gobsmacked as my British friends would say as to have such a small antenna can pull signals out of the ether that are that low in frequency and do it so quietly. I had always assumed that it would pick up more noise than signal but other than the 30 kHz spur from my switching power supplies the visual spectrum is pretty quite as you can see from the Spectran display. 

As with most VLF receivers used in the city, an external second order (series mylar capacitor and molded inductor shunted to ground) high pass filter was added to knock down the AC 60 Hz RFI and a mic attenuation resistor L-pad was added to bring the line level output down (as shown in the Spectran quickstart). There's enough room in the SuperSID's tin can to add the componetns. Righ now it's all on an external mini-solderless breadboard.

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