AM/FM Receiver Molecule

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	(generator "eeschema")
	(generator_version "10.0")
	(uuid "18f8ede3-13f1-5c50-9c4a-943343ee2478")
	(paper "A3")
	(title_block
		(title "AM/FM Receiver Molecule - discrete BJT/op-amp radio, STM32 USB audio")
		(date "2026-10-02")
		(rev "B (molecule)")
		(company "Adom")
		(comment 1 "4-layer PCB, JLCPCB-compatible rules")
		(comment 2 "Generated from tools/design.py (single source of truth)")
	)
	(lib_symbols)
	(text "AM/FM RECEIVER MOLECULE  -  discrete BJT + op-amp radio, STM32G0B1 USB audio"
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		(uuid "79a0e2cd-4299-5691-9113-322db6091e0c")
		(property "Sheetname" "FM_Frontend"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "4"))))
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	(text "Antenna, diplexer & FM front end"
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		(uuid "11cccc3d-2cd0-52d1-b958-9821a4bfaa4f")
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	(text "FM: high-side LO, IF 10.7 MHz.  Varactor tanks use BB910 through a 22 pF"
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	(text "series capacitor (reduces RF swing on the diode and sets the tuning"
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	(text "ratio)."
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		(uuid "9f5090b5-2c4c-5b92-be88-c8ef3f1fdbd4")
		(property "Sheetname" "AM_Frontend"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "5"))))
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	(text "AM front end (up-conversion to 10.7 MHz)"
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		(uuid "351856e6-555e-55aa-8c92-f838e4b9519c")
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	(text "AM 530-1700 kHz is up-converted with a high-side LO at 11.23-12.4 MHz; the"
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	(text "image lands at 22-23 MHz and is removed by the 2 MHz LPF, so no tracking"
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	(text "preselector is needed."
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		(property "Sheetname" "IF_10M7"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "6"))))
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	(text "10.7 MHz IF & second conversion to 455 kHz"
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	(text "Two 10.7 MHz ceramic filters (230 kHz) around one BJT gain stage, then a"
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	(text "BJT mixer with a 10.24 MHz crystal oscillator converts both bands to 455"
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	(text "kHz."
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		(uuid "cde52c28-1d11-5b9f-8b34-c0367b9766c5")
		(property "Sheetname" "AM_IF"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "7"))))
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	(text "AM 455 kHz IF, AGC & envelope detector"
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		(uuid "66bd3833-7be3-5e27-9f07-160805c455bb")
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	(text "Gain is set by the tail currents of two BC847BS differential pairs (~40 dB"
		(exclude_from_sim no)
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	(text "range each); an op-amp integrator holds the detected carrier at ~1 V."
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		(uuid "7f492491-f31d-57a8-93ce-fded8f627f19")
		(property "Sheetname" "FM_IF"
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		(property "Sheetfile" "fm_if.kicad_sch"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "8"))))
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	(text "FM 455 kHz limiter & pulse-count discriminator"
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		(uuid "6fd185c1-cbfb-5227-8902-0e36b68ddd90")
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	(text "Each IF cycle transfers a fixed charge C*(Vpp-2Vf) into the op-amp summing"
		(exclude_from_sim no)
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	(text "node, so the average current is proportional to frequency (40 uA at 455"
		(exclude_from_sim no)
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	(text "kHz, +/-6.6 uA at +/-75 kHz)."
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		(uuid "1b671d19-7e31-5203-b3cc-27ac66ed76b2")
		(property "Sheetname" "Tuning_UI"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "3"))))
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	(text "Tuning, band switching & user interface"
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	(text "DAC outputs are scaled x1.45 by rail-to-rail op-amps to 0-4.8 V and"
		(exclude_from_sim no)
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	(text "heavily RC filtered (varactor noise = LO phase noise).  The RF tracking"
		(exclude_from_sim no)
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		(uuid "1f8b1e81-9405-5867-a4f0-f8ae7eb84324")
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	(text "tank uses a filtered 12-bit PWM."
		(exclude_from_sim no)
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		(uuid "2738da20-9d15-563d-9b64-92a28c584021")
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	(sheet
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		(property "Sheetname" "Power_MCU"
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		(property "Sheetfile" "power_mcu.kicad_sch"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "2"))))
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	(text "Power, USB & MCU"
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	(text "USB-C 5 V in -> PTC -> +5V.  AP2112K LDO -> +3V3 (MCU).  Ferrite-filtered"
		(exclude_from_sim no)
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	(text "+5VA (all analog/RF) and +3.3VA (MCU VREF+: ADC / DAC reference).  The"
		(exclude_from_sim no)
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	(text "STM32G0B1 runs USB from HSI48 + CRS and its timers from a 40 MHz crystal;"
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	(text "a blank chip boots straight into the ROM USB DFU bootloader."
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		(uuid "f309d33b-72b0-50df-988d-26802f658409")
		(property "Sheetname" "Molecule_IO"
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		(instances (project "amfm_receiver" (path "/18f8ede3-13f1-5c50-9c4a-943343ee2478" (page "9"))))
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	(text "Molecule interface: machine pins & contacts"
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	(text "Adom Molecule (Molecule Design Guide v1.0): large / standard machine pins"
		(exclude_from_sim no)
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	(text "in the four corners, 96 x 96 mm apart on the 32 mm large grid (mounts"
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	(text "directly on the base scaffold), and medium machine contacts on the 2 mm"
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	(text "grid measured from MP1.  All four corner pins are GND; 5 V comes in on the"
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	(text "VIN contact (MC1) or USB-C.  None of the contacts is needed in use: power,"
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		(uuid "23ecbd87-51ef-5c8a-bde0-f89c2807aa08")
	)
	(text "control, audio and firmware updates all run over USB-C.  SWD, UART and the"
		(exclude_from_sim no)
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		(uuid "e0b98661-5540-5355-a1ad-c076c6f5b7ef")
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	(text "audio outputs are optional debug / monitor points; CLK(=BOOT0)/3V3 and"
		(exclude_from_sim no)
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	(text "RST/GND are adjacent pairs for jumper recovery."
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	(text "SIGNAL FLOW"
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	(text "ANT -> diplexer -> FM: 88-108 MHz RF amp (tracked varactor tank) -> BJT mixer <- 98.7-118.7 MHz VCO"
		(exclude_from_sim no)
		(at 20.32 240.12 0)
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	(text "             -> AM: 0.53-1.7 MHz preamp -> BJT mixer <- 11.23-12.4 MHz VCO (up-conversion)"
		(exclude_from_sim no)
		(at 20.32 244.02 0)
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	(text "both -> 10.695 MHz IF (2 ceramic filters + BJT amp) -> BJT mixer <- 10.24 MHz XO -> 455 kHz"
		(exclude_from_sim no)
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		(effects (font (size 1.6 1.6)) (justify left bottom))
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	(text "AM: ceramic filter -> 2x diff-pair VGA -> post-amp -> diode detector -> op-amp AGC & 5 kHz LPF"
		(exclude_from_sim no)
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		(effects (font (size 1.6 1.6)) (justify left bottom))
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	(text "FM: BJT limiter -> squarer -> diode-pump pulse-count detector -> op-amp integrator -> 15 kHz LPF"
		(exclude_from_sim no)
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		(effects (font (size 1.6 1.6)) (justify left bottom))
		(uuid "2571995c-a19a-5cd6-a57b-79d2a7e3f5dd")
	)
	(text "STM32G0B1: ADC samples AM_AUDIO / FM_AUDIO; DAC1/DAC2 tune the VCOs; PWM tunes the FM preselector;"
		(exclude_from_sim no)
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		(effects (font (size 1.6 1.6)) (justify left bottom))
		(uuid "051fe4c9-765f-555d-84bf-49853503c42f")
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	(text "TIM2_ETR counts the limited IF; TIM1 injects 40 MHz-crystal-derived markers at ANT for self-calibration."
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		(uuid "cae6d8e0-86ed-59f0-b721-93ae5659a102")
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	(text "USB-C only: UAC audio + CDC control port + DFU runtime; a blank chip boots into ROM USB DFU."
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	(text ""
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	(text "POWER: USB-C 5 V or VIN machine pin (B5819W OR-ing, 500 mA PTC).  AP2112K 3.3 V.  +5VA for analog/RF."
		(exclude_from_sim no)
		(at 20.32 275.22 0)
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		(uuid "7acb7b6f-8669-59a3-aafd-cdd62cee9083")
	)
	(text "Band switching: PNP high-side switches (MCU open-drain) power only the active front end."
		(exclude_from_sim no)
		(at 20.32 279.12 0)
		(effects (font (size 1.6 1.6)) (justify left bottom))
		(uuid "25ad8223-f9fd-5872-8e02-d65add158619")
	)
	(text "ADOM MOLECULE: large/standard GND machine pins 96 x 96 mm, 28 medium contacts on the 2 mm grid (all optional)."
		(exclude_from_sim no)
		(at 20.32 283.02 0)
		(effects (font (size 1.6 1.6)) (justify left bottom))
		(uuid "08459ca1-515a-5a00-98c1-db8fd7c58ec1")
	)
	(text "PCB: 4 layers - F.Cu signal / In1.Cu solid GND / In2.Cu power / B.Cu signal + GND pour."
		(exclude_from_sim no)
		(at 20.32 286.92 0)
		(effects (font (size 1.6 1.6)) (justify left bottom))
		(uuid "14868f9a-120c-5a31-af98-be1947f02a84")
	)
	(sheet_instances (path "/" (page "1")))
	(embedded_fonts no)
)