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This page describes the Directional Coupler/Reflectometer for the rev0SNA 50-2500 MHz Scalar Network Analyzer.

==Summary==
[[File:Rev0VTx_VCO_Sch.png|thumb|right|Schematic for the rev0VTx VCO.]]
[[File:Rev0VTx_VCO_Brd.png|thumb|right|Board for the rev0VTx VCO.]]

The Directional Coupler/Reflectometer is based around the Mini-Circuits [http://www.minicircuits.com/pdfs/JDC-20-5.pdf JDC-20-5] 50-1500 MHz and [http://www.minicircuits.com/pdfs/SYD-20-33+.pdf 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 <s>15dB</s> return loss (1.13:1 <s>1.45:1</s> VSWR) at the 2m ham band, and +/-3dB error at 11.3dB <s>20dB</s> return loss (1.75:1 <s>1.22:1</s> 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).

[[File:Ant_meas_s11-vs-dcpl.png|thumb|center|480px|Antenna measured via VNA directly vs. via directional coupler illustrating error vs. return loss and directivity.]]
[[File:Sna_lfdcpl_performance.png|thumb|center|480px|Performance characteristics of the low frequency side of the directional coupler.]]

==Revisions==
* '''1.0''': Initial revision.

==Bill of Materials (v1.0)==
{| border="1"
|style="text-align:center;" |'''Part'''
|style="text-align:center;" |'''Quantity'''
|style="text-align:center;" |'''Unit Cost'''
|style="text-align:center;" |'''Total Cost'''
|style="text-align:center;" |'''Source'''
|-

|JDC-20-5
|1
|style="text-align:right;" |$17.95
|style="text-align:right;" |$17.95
|[http://www.minicircuits.com/MCLStore/ModelInfoDisplay?13814347187460.8652138723612826 Mini-Circuits]
|-

|SYD-20-33+
|1
|style="text-align:right;" |$21.95
|style="text-align:right;" |$21.95
|[http://www.minicircuits.com/MCLStore/ModelInfoDisplay?13814347373100.3808422130685456 Mini-Circuits]
|-

|SKY65017
|1
|style="text-align:right;" |$1.63
|style="text-align:right;" |$1.63
|[http://www.digikey.com/product-detail/en/SKY65017-70LF/863-1063-1-ND/2052195 Digi-Key]
|-

|AS179-92LF
|3
|style="text-align:right;" |$0.52
|style="text-align:right;" |$1.56
|[http://www.digikey.com/product-detail/en/AS179-92LF/863-1003-1-ND/2052158 Digi-Key]
|-

|74LVC1GU04
|1
|style="text-align:right;" |$0.38
|style="text-align:right;" |$0.38
|[http://www.digikey.com/product-detail/en/74LVC1GU04GW,125/568-4839-1-ND/2116535 Digi-Key]
|-

|0402 100nF Capacitor
|11
|style="text-align:right;" |$0.011
|style="text-align:right;" |$0.12
|[http://www.digikey.com/product-detail/en/C1005X5R1A104K050BA/445-1265-1-ND/567732 Digi-Key]
|-

|0402 10pF Capacitor
|1
|style="text-align:right;" |$0.0116
|style="text-align:right;" |$0.01
|[http://www.digikey.com/product-detail/en/C1005C0G1H100D050BA/445-1235-1-ND/567743 Digi-Key]
|-

|0603 Capacitor
|6
|style="text-align:right;" |$0.0096
|style="text-align:right;" |$0.06
|[http://myworld.ebay.com/mib_instruments eBay - mib_instruments]
|-

|0402 Resistor
|10
|style="text-align:right;" |$0.025
|style="text-align:right;" |$0.25
|[http://myworld.ebay.com/mib_instruments eBay - mib_instruments]
|-

|0603 Ferrite Bead (1500 Ohm)
|1
|style="text-align:right;" |$0.21
|style="text-align:right;" |$0.21
|[http://www.digikey.com/scripts/DKSearch/dksus.dll?Detail&itemSeq=137909071&uq=635170159706315007 Digi-Key]
|-

|Male Header
|3
|style="text-align:right;" |$0.01
|style="text-align:right;" |$0.03
|[http://www.ebay.com/ eBay]
|-

|SMA Female Connector
|3
|style="text-align:right;" |$3.37
|style="text-align:right;" |$10.11
|[http://www.digikey.com/product-detail/en/CONSMA003.062/CONSMA003.062-ND/1577208 Digi-Key]
|-

|PCB
|1.725"x0.95"/3
|style="text-align:right;" |$10.00
|style="text-align:right;" |$5.46
|[http://dorkbotpdx.org/wiki/pcb_order Laen's PCB]
|-

|'''Total Unit Cost'''
|
|
|style="text-align:right;" |'''$59.72'''
|
|-
|}

==PCB/Construction Photos==
<gallery perrow=3 widths=240px heights=120px>
File:rev0VTx_VCO_PCB_Bottom.jpg|Bottom of unpopulated PCB
File:rev0VTx_VCO_PCB_Top.jpg|Top of unpopulated PCB
File:rev0VTx_VCO_Top.jpg|Populated PCB
</gallery>

SNA DCpl - Revision history

WikiSysop: Created page with "{{navup |previous=SA_LPF |up=Spectrum_Analyzer |next=SA_MIX1}} This page describes the Directional Coupler/Reflectometer for the rev0SNA 50-2500 MHz Scalar Network Analyzer...."