SNA DCpl
This page describes the Directional Coupler/Reflectometer for the rev0SNA 50-2500 MHz Scalar Network Analyzer.
Summary
The Directional Coupler/Reflectometer is based around the Mini-Circuits JDC-20-5 50-1500 MHz and SYD-20-33 30-3000 MHz 20dB Directional Couplers. The PCB includes a SKY65017 20dB amplifier, three SPDT RF switches, and necessary support components to allow switching between the low-frequency optimized JDC-20-5 coupler and high-frequency optimized SYD-20-33 coupler. The expected performance is >20dB directivity from 50-2500 MHz, allowing a +/-3dB error at 10dB return loss (2:1 VSWR) across the frequency range, with +/-3dB error at 24dB 15dB return loss (1.13:1 1.45:1 VSWR) at the 2m ham band, and +/-3dB error at 11.3dB 20dB return loss (1.75:1 1.22:1 VSWR) at the 70cm ham band.
Testing
- 11.17.2013: The PCB was assembled with all components.
- 11.18.2013: Through testing it was determined that the PCB was designed incorrectly to only display forward coupling, rather than reverse (needed to measure reflection power). The low frequency coupler was re-routed via semi-rigid coax to the correct orientation. Test results show >20dB directivity from 10-540 MHz, less than the datasheet specification of 50-1500 MHz (seen below).
Revisions
- 1.0: Initial revision.
Bill of Materials (v1.0)
Part | Quantity | Unit Cost | Total Cost | Source |
JDC-20-5 | 1 | $17.95 | $17.95 | Mini-Circuits |
SYD-20-33+ | 1 | $21.95 | $21.95 | Mini-Circuits |
SKY65017 | 1 | $1.63 | $1.63 | Digi-Key |
AS179-92LF | 3 | $0.52 | $1.56 | Digi-Key |
74LVC1GU04 | 1 | $0.38 | $0.38 | Digi-Key |
0402 100nF Capacitor | 11 | $0.011 | $0.12 | Digi-Key |
0402 10pF Capacitor | 1 | $0.0116 | $0.01 | Digi-Key |
0603 Capacitor | 6 | $0.0096 | $0.06 | eBay - mib_instruments |
0402 Resistor | 10 | $0.025 | $0.25 | eBay - mib_instruments |
0603 Ferrite Bead (1500 Ohm) | 1 | $0.21 | $0.21 | Digi-Key |
Male Header | 3 | $0.01 | $0.03 | eBay |
SMA Female Connector | 3 | $3.37 | $10.11 | Digi-Key |
PCB | 1.725"x0.95"/3 | $10.00 | $5.46 | Laen's PCB |
Total Unit Cost | $59.72 |
PCB/Construction Photos
- Rev0VTx VCO PCB Bottom.jpg
Bottom of unpopulated PCB
- Rev0VTx VCO PCB Top.jpg
Top of unpopulated PCB
- Rev0VTx VCO Top.jpg
Populated PCB