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Thanks for comments "Prog"
My comment on "reduced noise compared to a log wire". On first testing my loop out in the garden it was - where did all those signals come from ??? "80m and 40m are alive!" And as I've already said excellent MW DX - best so far is good signals from S Korea and Tiwan at 900 km (5600 miles). And during to 2019 SpE season it gave much better results than 70 MHz dipole when receiving the Eastern European OIRT band (66-74 MHz). And it is really good on the Bnd - apart fom being wide angle bi-directional.
Pre-amp gain of about 20 dB is about right - I have to use a 10 dB attenuator to avoid putting too much signal into the SDR. But at around £6 inc. for a ready made board it was the simplest option.