Thursday, September 27, 2012

Noise bridge

I had this project unfinished for a long time although I had already used the noise generator part from the circuit (left part) but not the noise bridge (from C5 to the right).

The schematic:

The original were I based mine was from here ...if I remember...

Honestly I changed the schematic a little bit, didn't placed the calibration caps... will put latter on, just wanted to check resistive impedance for now.
Tested against my wire dipole just to discover that it's resonant near 19.4 Mhz, think this time I cut the wire a little to short....

Crosschecking the same dipole with the antenna analyzer:

Spot on! I can discharge the MFJ :)

I tested the circuit with another antenna, in this case a loop for 500Khz but didn't got a null so must check again directly to the loop and not to the coupling part, there's also a chance I passed the resonance frequency without noticing it.

If you want a simple and cheap way to check antennas this is still need a receiver tough...

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