On 10/28/2014 5:24 PM, Lostgallifreyan wrote:
rickman wrote in :

I have a project in mind that would need a very good antenna in the
frequency range of 60 kHz. Originally I looked at loop antennas and
liked the idea of a large shielded loop made of coax tuned with a
capacitor. My goal is to get as large a signal as possible from the
antenna and matching circuit to allow the use of a receiver with very
low sensitivity... in fact an all digital receiver.


MSF time signals? Just a thought... If you're interfacing an analog signal to
digital, one trick I used (for audio but it ought to help here too) is a
CA3140 with a bit of positive feedback through a few Mohms for hysteresis to
clean the signal a bit. The resulting Schmitt trigger, powered by about 5 or
6V, could be sensitive to take a lot of strain off your antenna. Whether this
alone gives you enough gain I don't know, but it is cheap to try.

Thanks for the suggestion. I'm not sure this would be any better than
feeding it directly into my digital input. That is a differential input
and I expect to use feedback to overcome the residual input offset. So
the input will be pretty sensitive, the question is whether I need mV
level signals or maybe just uV signals which might not require an amp.
By using positive feedback the threshold would be shifting and the
amount of level shift would set the floor for the signal level from the
antenna I think.

--

Rick