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Main Board
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ChangeDescription
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Grounding
Fill in gaps in groundplane.
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Teensy ground pins
V11 has 2 of 3 ground Teensy ground pins floating. Connect those pins to ground.
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Remove audio preamp
The 2 transistor audio preamp is not necessary. The DAC has plenty of headroom to drive the audio amplifier.
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Change 1/8 jacks
Swap the through-hole jacks with surface mount. Digikey part: https://www.digikey.com/en/products/detail/cui-devices/SJ-3524-SMT-TR/281298
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Add jack for key
It is possible changing to surface mount jacks will free up enough room for a CW key jack.
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Off-board audio processing
I picked up the audio signal from TP1 of the main board and amplified it with an LM 386 audio amplifier mounted on seperate
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board. This significantly elimated the processor noise which was otherwise coupled in to the audio section of the main board . Steve K8ZBE
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Neville, ZL2BNE:
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Add 470uF on Teensy pins Vin & Gnd
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Strap Teensy Gnds
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Strap Teensy Gnd to AGnd on PCM5102
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Bypass audio preamp, essentially connect TP1 to TP2
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David Cripe NM0S
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The crystal for the Si5351 must have between 6 and 12 pF load capacitance. Y1 should be replaced with a part in a 4-SMD package, as HC-49 packaged crystals all have higher load C.
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Add pin headers for the speaker output and Key1, Key2 and PTT signals, rather than add another audio jack.
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Add ferrite beads and TVS diodes on the MIC, PTT, Key1 and Key2 lines
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Add 470uF at audio amp, pin 3 to gnd.
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Add a rear-panel switch to shut off boost PS for operating unit in receive mode only.
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K9HZ:
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Delete Si5351 from Main board
Moved the Si5351 from the main board to the combined QSE/QSD board for better IF signal propagation.
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Added boards for Encoders.
Developed boards to mount encoders on. Simplifies cabling of encoders.
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Outboarded I2C for other boards
Added connector for I2C bus used for Si5351 on QSE/QSD, filter selection on filter board, RF attenuators on QSE/QSD.
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Voltage Regluators
Added board voltage regulators for 5V/ 3.3V to decouple noise from other boards
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