Mike,
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What you are seeing sounds like correct behavior to me for Q508 when in receive mode with RX at 3.3v.
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L502 holds the source pin at ground for DC, any received signal is in the microvolts, and very hard to detect.
With the gate pin at 3.3v, the transistor is on, so the weak pullup resistor at R510 is overpowered and the drain pin is also at ground.
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D516 prevents any large voltage spikes from from destroying the receiver front end when transmitting.
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I'm not sure how to cure your problem, but Q508 may be working correctly.
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Jerry, KE7ER
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On Mon, Apr 21, 2025 at 10:19 AM, Mike, KL7MJ wrote:
Stan,
I¡¯m seeing 0 on S and D, and 3.3 on the gate.?
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