LF/MF WSPR with CCW Vertical Dipole Antenna

Robert, VA3ROM

Well, it seems that while the high bands were affected by the latest solar coronal hole G1/G2 storms the really low end of the bands improved, at least for my location. One port of the antenna feeds my KiwiSDR and it's providing excellent results down to its bottom of it's reception range at 10 kHz, so no problems picking up the VLF beacons from Japan, Australia across NA to Europe in the upper VLF range. I managed to track down and remove all local RFI noise sources in the shack, which made a big difference. Now if I could just get the neighbourhood to do the same ;) But I do have an RFI quiet site up at my summer trailer site (no Wi-Fi, AC, landlines, cellular, etc.) that I'll have to try and see if there's much difference in the VLF reception.

I've attached a couple of the lastest LF and MF WSPR beacon captures plus a partial late night VLF sound card receiver capture using Spectrum Labratory. Big improvement over the last week reception wise.

I noticed that some of the KiwiSDR's labels are incorrect but that's a minor issue added to the never ending list of minor fixes for John ZL/KF6VO to look at. But he's been busy with other programming enhancements for the KiwiSDR. I use it to calibrate my VLF receivers running the SuperSID software microphone input levels in dBm. Hard to compare receivers when one is calibrated to a known reference and the others are all different given each sound card's electronic variations. But sound cards do make excellent VLF receivers and my 80 m sloper seems to be doing very well. It's plugged into one laptop microphone input sampling at 96 kHz couple to the antenna with a simple second order high pass filter and a couple of back to back IN914's to protect the input from strong atmospheric (lightning crashes). The high pass filter really knocks down the signals below 18 kHz, which increases the SNR for the VLF beacons I'm interested in receiving. Like night and day with the high pass filter in and out of circuit, Glad that I bought a good selection of Mylar capacitors because they are the ones to use in low power AC frequency. And I was wondering what I was going to do with those low value mH miniature molded inductors that I never seemed to have any radio circuit use for. They also work great for audio filter circuits connected to sound cards.


PS Note the sudden and sharp drop that happened with the VLF beacons just after 0600Z this morning. It started with Cutler, ME (NAA) and moved across to Lamoure, ND (NML) in my time zone. The only think I could see was that the Kp index suddenly shot up to 4.33 between 03-06Z then back down to 3 between at 06-09Z. I didn't think that that could happen on the dark side of the Earth. The fact that it roll across the continent from east to west with a slight delay and then getting strong as it went by my location is interesting. Shades of long delayed echos and weird or what, eh? I'm seeing another interesting ionospheric effect on the Lualaulei, HI (NPM) beacon that looks like a "bouncing ball" curve in this mornings recordings! 

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