1 year from my first attempt to receive the SAQ transmission (see above).
For this time, I tried in an open field from the west side of my city (Bucharest), using a ferrite antenna, an active converter with SA612 and my IC-7300 transceiver.
The ferrite antenna has an inductance of 18 mH and is tuned on 17.2 KHz with a fixed 4.7nF capacitor and a variable one (15-550 pF). The converter is the typical schematic from the NE612 application note, but I put in the front of it an RF cascode preamp (FET+BJT) – around 20dB @12V. The carrier crystal is 10.7 MHz.
Here is the preamp schematic and LTSpice simulations results:
The 4uH coil is made only for test & measuring reasons (is a matching to 50 ohm port of my test equipment); after the alignment, I simply removed it.
And this is my open field setup (cclick to enlarge) :
This is a clip from the first transmission (9 UTC):
The frequency is 10717.25 ; it has a small 50Hz lift, but I didn’t tried to readjust.
I have a todo list for some improvements of the VLF converter, I will return to publish the project when will be ready.