Really odd problem with Flipper's Lite. We are not sure if it came this way or if this is a problem that has happened over time.
We were testing with nothing attached to the Lite, except the end caps. We had programmed in your latest test firmware and looking at the noise of S21 in the 9KHz to 1MHz range. There is a 20dB step in the noise at 400kHz where it jumps from 80dB to 60dB. There is no calibrations applied. We rolled it back to the last released firmware and it had no effect. If we change the sweep range to 1M to 100M, its roughly 60dB.
If we run it standalone disconnected from the PC, S21 drops to 80dB. Plugging in the USB cable (but not running any software), it jumps back up to 60dB with the step at 400kHz.
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We tried different ports on the PC as well as used a powered hub and different cables, no effect.
Taking the unit apart, it appears the same as my Lite. We removed the battery and ran it from the PC, noise still present. Totally different from how mine behaves.
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We tried a few different PCs, again no effect. Shown also is sweeping Flipper's from 1M to 100MHz.
For comparison, my Lite is shown in J1&2. The USB port on mine seems to have no effect.