Thanks for sharing this interesting paper. Well, the circuit looks quite
complex but the image of the final construction looks compact.
Since we got access to 472 kHz a weeks ago, i need another receive
antenna now, since all my front ends are resonanted, i.e. mono band. So
the advantage of a single receive antenna becomes more and more
convincing to me. Of course it needs a high dynamic range without
distortion of the spectrum then..
A question: The DC supply voltage is connected to e.g. C16?
It's connected by way of the output pin, so you send the DC supply right
up the coax instead of having to run additional wires. You'll need a bias tee
down at the receiver end, and I describe one at the end of this paper:
What might be the lower cutoff frequency if values for the input LP and
HP filters are well choosen? It should be possible to extend the circuit
to the VLF range (?).
The amplifier itself without the input filter will go down to about
100-200kHz. To go lower than that you'll need to increase to capacitor values
plus change the transformer core material to Fair-Rite 77 or something similar.
N7ZWY / WDX3HLB
Senior Member IEEE