Re: AirSpy You Loop Passive Magnetic Loop antenna ? #airspydiscovery

jdow
 

The high end of HF, nonetheless, is the end at which the natural noise is minimum. So you (may) need more gain there. The other choice is your main frequency range of interest. Pick a spot, usually towards the top end, and adjust there.

If somebody has managed to un-pot the circuit they might discover the pot is an adjustment for operating current. Adjust until you are near the transistor's dissipation limits. Then put a variable attenuator between the receiver and the bias-t and adjust THAT the way I suggested. The adjustment optimizes dynamic range without messing up signal to noise ratios.

{^_^}

On 20200323 17:22:02, DXer wrote:
On Mon, Mar 23, 2020 at 07:20 PM, jdow wrote:
Adjust from low gain upwards until the SNR on weak signals stops improving
on the highest frequency which is of interest.
In my limited experience, using the highest frequency as reference does not work with this loop.
Performance varies wildly from LF to the top of HF range. It's not linear, not logarithmic, it's random.
Vince

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