Quote:
Originally Posted by Bazz4CQJ
This is not working at all well, with just one or two very weak signals being heard.
........ or is there any other factor(s) which could account for the lack of performance?
Thanks
B
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Just a glance at the schematic, unless I'm missing something really obvious, I wouldn't expect this setup to work very well at all.
I have experimented with loops for many years as transmitting antennas and through the principle of reciprocity a good transmitting antenna is likely a good receiving antenna. With loops, for any reasonable efficiency they have to be resonant at the receiving or transmitting frequency. Just as the loop-stick in your transistor radio has to be, or the frame antenna in your valve radio.
The schematic just shows the loop connected into an LNA. It ideally needs a capacitance (varicap) or V/C to tune it and a loop tap and/or impedance matching transformer to feed the LNA and be peaked on the frequency of interest to get the best out of it.
I appreciate the idea of an untuned broadband antenna, it will be self resonant somewhere though, but I would not expect it would be a great performer at all at frequencies where it was not resonant.
So apart from the electrostatic shielding, which would be good at eliminating interference, I don't think that loop would be much chop, except at a frequency it was resonant and then it is not ideally matched to the LNA input.