Another set of questions: Given the high atmospheric noise level at
LF/VLF, is there really a need for such a large loop as you propose,
for receiving? How quiet is your receiver front end? In other words,
will such a large loop significantly improve your SNR on weak signals?
Do you have a reason other than signal level for using such a large
loop? What about the response to nearby strong electric-field noise
generators of a large loop versus a smaller one?

Cheers,
Tom