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| Joined: | Feb 7th, 2010 |
| Location: | Des Moines, Iowa USA |
| Posts: | 425 |
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I have one of these receivers. I have the one (in clockwise direction) 4th "black" receiver on top right side...this one is "SILVER" (aluminum) in color. His picture just had a shadow in it. With these receivers you need to be MILES away from electrical interference. Or the hum and buzz will tear your head off
mikesndbs wrote:Hi Joe
Been thinking about this today and have done some hook ups to check.
If I remove the choke from the diagram and instead use the 100K resistor in its place so as to give me a circuit, I hear mostly a 50hz hum from the mains here in the UK.
Could I filter this using passive components, but still keep this 'sniffer' sensitive to all other fqs?
Thanks
Mike
Mike,
Look at this circuitry for a way to boost vlf signals and reduce the power hum. This design is essentially an untuned radio receiver with vlf bandwidth. The filter cuts the hum.
http://www.auroralchorus.com/bbb4rx3.htm
Joe
You can actually "rub" the antenna on the ground and HEAR the noise in the headphones. I think these are actually an "amplification" circuit built without a proper input (antenna connected instead) *something like that.