4 layers75 × 42 mm
Xmit
tdunning/xmit
A simple low-power digital transmitter for amateur bands using new components
87 parts3
4 layers75 × 42 mm
Overtone
tdunning/xmit3A simple low-power digital transmitter for amateur bands using new components
- Size
- 75 × 42 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 37
- Nets
- 21
- Pads
- 92
- Tracks, vias
- 103, 14
- Pours
- 5
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 5 Jun 2026
- Updated
- 15 Jul 2026
Overview
Overtone is an open-source printed circuit board by tdunning, from the tdunning/xmit repository on GitHub. It is a 4-layer board of 75 × 42 mm with 37 parts on 21 nets, routed with 103 tracks and 14 vias.
It is built around the 74LVC1G66GW, SN74LVC1G04DBV and TPS7A2033PDBV, with the AO3407A among its other parts. Its parts include 10 capacitors, 7 resistors, 6 ICs, 5 inductors and 3 connectors.
Main components
4
74LVC1G66GW
SOT-353-40℃~+125℃ 1.65V~5.5V 11pF 155MHz 1:1 4.2ns 5.3ns 600ps 6Ω SOT-353 Analog Switches, Multiplexers ROHSNexperiaAnalog Switches, Multiplexers
SN74LVC1G04DBV
SOT-23-5-40℃~+125℃ 1 1 1.65V~5.5V 1.7V~2V 10uA 2.4V 3.7ns@5V,50pF 32mA 32mA 400mV 700mV~800mV 74LVC 电源关断保护 SOT-23-5 Inverters ROHSTexas InstrumentsInvertersTPS7A2033PDBV
SOT-23-5-40℃~+125℃@(Tj) 1 10uVrms 140mV@(300mA) 3.3V 300mA 65dB@(100kHz) 6V 8.5uA Fixed Over Current Protection、Short Circuit Protection、Thermal shutdown、Enable control、Input under-voltage protection、Output discharge、Built-in soft-start Positive SOT-23-5 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSTexas InstrumentsVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
AO3407A
SOT-231 P-Channel 1.4W 1.8V 14.3nC@4.5V 30V 37mΩ@10V、52mΩ@4.5V 4.2A 700pF 75pF SOT-23 MOSFETs ROHSUMWMOSFETs
README
README.mdXMIT - New tools for old jobs
This repository has design files and (soon) code for a direct synthesis digital mode transmitter optimized for use on amateur bands. It should work well up to 2m. The novelty here relative to other systems like the QDX lies in a few areas:
a) the use of 74LVC2G157 to generate differential drive for a differential driver such as the THS6232 which can directly drive most balanced antennas without a balun at up to about 5W. This design avoids the need for fancy gate drive or paralleling FETs in favor of SMT packaging everywhere.
b) the use of SMT inductors and SMT analog switches such as the 74lvc2g53 or 74lvc1g66. This change is not earth-shattering, but it allows a much tighter all-SMT design with as much as 80dB suppression of harmonics. The high degree of suppression is achieved by using a filter tuned to put the response zeros directly on the harmonics and careful filter layout to suppress parasitic coupling.
Transmit filtering
The design of the transmit chain uses one of a number of filters to reject harmonics of the main frequency. One of these filters is selected using analog switches to suit the desire transmission frequency. These filters are designed to have minimal attenuation in each of several amateur bands. Since these bands are relatively narrow, passband flatness is not a grave concern. The zeros of the filters are positioned near the second or third harmonics of the carrier to suppress these frequencies very strongly. Higher harmonics have nearly 75dB of suppression.
The response curves for the filters designed so far are shown below.
Parts
37| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 1µ | Capacitor_SMD:C_0805_2012Metric | C201, C202, C203, C205 |
| 4 | ~ | MountingHole:MountingHole_2.2mm_M2 | H501, H502, H503, H504 |
| 3 | 74LVC1G66 | Package_TO_SOT_SMD:SOT-23-5 | U103, U104, U106 |
| 2 | 100 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R103, R104 |
| 2 | 15nH | Inductor_SMD:L_0805_2012Metric_Pad1.05x1.20mm_HandSolder | L103, L106 |
| 2 | 18pF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C108, C111 |
| 2 | 1nF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C112, C113 |
| 2 | 200k | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R201, R202 |
| 2 | SN74LVC1G04DBV | Package_TO_SOT_SMD:SOT-23-5 | U101, U105 |
| 2 | ~ | TerminalBlock_TE-Connectivity:TerminalBlock_TE_282834-2_1x02_P2.54mm_Horizontal | J502, J503 |
| 1 | 100 | Resistor_SMD:R_0603_1608Metric | R203 |
| 1 | 150nH | Inductor_SMD:L_0805_2012Metric_Pad1.05x1.20mm_HandSolder | L105 |
| 1 | 1k | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R108 |
| 1 | 1µH | Inductor_SMD:L_0805_2012Metric_Pad1.05x1.20mm_HandSolder | L201 |
| 1 | 2.2k | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R107 |
| 1 | 2.2p | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C109 |
| 1 | 39nH | Inductor_SMD:L_0805_2012Metric_Pad1.05x1.20mm_HandSolder | L104 |
| 1 | 6.8p | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C110 |
| 1 | AO3407A | Package_TO_SOT_SMD:SOT-23 | Q201 |
| 1 | LED | LED_SMD:LED_0603_1608Metric | D201 |
| 1 | TPS7A2033PDBV | Package_TO_SOT_SMD:SOT-23-5 | U201 |
| 1 | ~ | Connector_Coaxial:SMA_Samtec_SMA-J-P-H-ST-EM1_EdgeMount | J506 |
Questions
How big is the Overtone PCB?
It measures 75 × 42 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Overtone use?
37 parts, built around the 74LVC1G66GW, SN74LVC1G04DBV, TPS7A2033PDBV and AO3407A. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Overtone KiCad files?
From the tdunning/xmit repository on GitHub, at the commit this page was made from: the board is overtone/overtone.kicad_pcb and its schematic mixer-test/mixer-test.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Overtone design in my own project?
Its repository states no licence, so its author keeps all rights: ask tdunning before reusing the design.
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