Difference between pages "EP2C5-DB" and "RF Attenuators"

Revision as of 11:50, 7 September 2021

Homebrew RF Attenuators

Attenuators

30 dB Attenuator

Pi Attenuator Calculator

Built
- Standard 5% resistor values
- R1 = 820 in parallel with 22K = 790.6 ohms
- R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
- Flat from 0-30 MHz
- Measured attenuation is flat
  - -30.01dB at 1 MHz
  - -30.24dB at 30 MHz
- Input Impedance - 53.1 ohms, 21.3nF
- SWR 1.06
- 1/2W max (5VDC max, 0 ohm source)

NanoVNA scan data

LTSPICE Simulation

20 dB Attenuator

Build
- Standard 5% resistor values
- R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
- R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
- Flat from 0-30 MHz
- Measured attenuation is flat
- Input Impedance - tbd ohms, tbd nF
- SWR tbd
- 1W max (8.6 V max, 0 ohm source)

LTSPICE Simulation

10 dB Attenuator

File:Atten 10dB P115-720px.jpg

Build
- Standard 5% resistor values
- R1 = 2 of 150 in parallel also in parallel with 1.5K = 71.43 ohms (0.3% error)
- R2 = 3 of 330 Ohm 1/4W parallel resistors paralleled with 810 ohms = 96.85 ohms (0.62% error)
- Flat from 0-30 MHz
- Measured attenuation is flat
- Input Impedance - tbd ohms, tbd nF
- SWR tbd
- 3/4W max (9.1 V max, 0 ohm source)

File:10dB Attenuator NanoVNA Setup Curve 900MHz.PNG

File:10dB Attenuator NanoVNA Data 900MHz.PNG

LTSPICE Simulation

Attenuator Construction

Single side copper clad PCB
- Approx 2"x1"
Clean with steel wool
Solder SMA connectors
- Use large alligator clips to hold while soldering
- Solder on sides only

Cut "T" Shaped pads
- I used nibbler
Center fits between connector ground pins
Glue down pads with Superglue

Solder center pin with big solder blob
- A bit too high for direct contact
Verify raised pad does not short to ground

Solder side resistor(s)
Leave room for center resistor(s)

Measure side resistors from pad to ground
Should match value
Solder center resistor(s)

Verify no shorts between centers and ground

References

Difference between pages "EP2C5-DB" and "RF Attenuators"

Revision as of 11:50, 7 September 2021

Contents

Homebrew RF Attenuators

Attenuators

30 dB Attenuator

20 dB Attenuator

10 dB Attenuator

Attenuator Construction

References

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@@ Line 1: / Line 1: @@
-[[File:tindie-mediums.png|link=https://www.tindie.com/products/land_boards/z80-6502-6809-fpga-multicomp-pcb-ep2c5-db/]]
+== Homebrew RF Attenuators ==
-<video type="youtube">7O0njivn-Po</video>
+[[file:Atten_30dB_20dV_P1812-720px.jpg]]
-== EP2C5-DB FPGA card ==
+== Attenuators ==
-[[File:P971-cropped-720px.jpg]]
+[[file:Chart_mW_vs_dbM.PNG]]
-I love [http://searle.x10host.com/Multicomp/index.html Grant Searle's Multicomp project]. It lets you easily create 6502, Z80, 6809 Retrocomputers of the late 1970s era. This card provides all of the connections needed.
+=== 30 dB Attenuator ===
-Grant's original design used an EP2 and that's exactly what this cards USES. Note that's not compatible with the latest version Altera/Intel Quartus but you can download older versions like 13.1 SP. Just make sure it supports the Cyclone II family of FPGAs. We also have an [https://www.tindie.com/products/land_boards/z80-6502-6809-fpga-multicomp-pcb-retro-ep4/ EP4 version of this card for sale on Tindie].
+* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
-== Features ==
+[[file:Atten30dB_P116-720px.jpg]]
-* [[Cyclone II EP2C5 Mini Dev Board]]
+[[file:30dB_Attenuator.PNG]]
-** [https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=EP2c5+fpga+board&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=EP2+fpga EP2C5T144C8N FPGA Card] - Ebay listing
-* 6 bit video on VGA (2:2:2 R:G:B)
-* 128KB of SRAM for banked use in CP/M
-* PS/2 Keyboard Mini-DIN connector
-* Connector for serial ports
-** Can attach inexpensive FTDI USB to serial converter
-* SD Card
-* DC power jack (on FPGA card)
-=== EP2 Resources ===
+* Built
+** Standard 5% resistor values
+** R1 = 820 in parallel with 22K = 790.6 ohms
+** R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
+** Flat from 0-30 MHz
+** Measured attenuation is flat
+*** -30.01dB at 1 MHz
+*** -30.24dB at 30 MHz
+** Input Impedance - 53.1 ohms, 21.3nF
+** SWR 1.06
+** 1/2W max (5VDC max, 0 ohm source)
-* EP2CE5 had 13 of 1Kx9 SRAM blocks
+* NanoVNA scan data
-[[File:EP2XX_Resources.PNG]]
+[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
-== Stackup with FTDI Card ==
+[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
-[[File:P1752-CROPPED-720PX.jpg]]
+* LTSPICE Simulation
-* [[FTDI-49MM]]
+[[file:LTSPice_30dB.PNG]]
-== VGA - Ideal Drive 2:2:2 Case ==
+=== 20 dB Attenuator ===
-* FPGA has a 3.3V driver which can drive 8 mA
+[[file:Atten_20dB_P115-720px.jpg]]
-* Ideal case drive current
-** 0.7V into 75 Ohms = 9.33 mA
-* R-2R values
-** Ideal resistor values are 417.9 ohms and 835.7 ohms
-** [http://www.brannonelectronics.com/images/STANDARD%20VALUE.pdf Standard value 1% resistors]
-** 1% standard values are [https://www.mouser.com/ProductDetail/652-CR0805FX-4220ELF 422 (Mouser)], [https://www.mouser.com/ProductDetail/603-RC0805FR-07845RL 845 (Mouser)] Ohms
-*** Get closest values
-*** 0V, 0.228V, 0.460V, 0.693V
-* Voltage steps are:
-[[File:VGA_Sim_2R_Voltage.PNG]]
+[[file:20dB_Attenuator.PNG]]
-* Current steps are:
+* Build
+** Standard 5% resistor values
+** R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
+** R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
+** Flat from 0-30 MHz
+** Measured attenuation is flat
+** Input Impedance - tbd ohms, tbd nF
+** SWR tbd
+** 1W max (8.6 V max, 0 ohm source)
-[[File:VGA_Sim_2R_Current.PNG]]
+[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
-== Connectors ==
+[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
-=== J1 - VGA ===
+* LTSPICE Simulation
-=== J4 - SD Card ===
+[[file:LTSPice_20dB.PNG]]
+=== 10 dB Attenuator ===
-=== J5 - Serial Ports 1/2 ===
+[[file:Atten_10dB_P115-720px.jpg]]
-* Connects to FTDI Module
+[[file:10dB_Attenuator.PNG]]
-# RTS
+* Build
-# RXD
+** Standard 5% resistor values
-# TXD
+** R1 = 2 of 150 in parallel also in parallel with 1.5K = 71.43 ohms (0.3% error)
-# GND
+** R2 = 3 of 330 Ohm 1/4W parallel resistors paralleled with 810 ohms = 96.85 ohms (0.62% error)
+** Flat from 0-30 MHz
+** Measured attenuation is flat
+** Input Impedance - tbd ohms, tbd nF
+** SWR tbd
+** 3/4W max (9.1 V max, 0 ohm source)
-[[File:EP2C5-DB_FTDI.PNG]]
+[[file:10dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
-==== FTDI Module ====
+[[file:10dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
-[[File:FTDI_rot.jpg]]
+* LTSPICE Simulation
-==== FTDI Wiring ====
+[[file:LTSPice_10dB.PNG]]
-** J5-1 (marked RTS on PCB) to FTDI CTS pin
+=== Attenuator Construction ===
-** J5-3 (marked RX on PCB) to FTDI TX pin
-** J5-5 (marked TX on PCB) to FTDI RX pin
-** J5-7 (marked GND on PCB) to FTDI GND pin
-[[File:EP2C5-DB_FTDI_Wiring.PNG]]
+* Single side copper clad PCB
+** Approx 2"x1"
+* Clean with steel wool
+* Solder SMA connectors
+** Use large alligator clips to hold while soldering
+** Solder on sides only
-=== J6 - 8-bit I/O connector ===
+[[file:Atten_01_SMAs_720px.jpg]]
-* FPGA Pins
+* Cut "T" Shaped pads
+** I used nibbler
+* Center fits between connector ground pins
+* Glue down pads with Superglue
-# 3.3V
+[[file:Atten_02_Pads_720px.jpg]]
-# 3.3V
-# 25
-# 31
-# 41
-# 40
-# 43
-# 42
-# 45
-# 44
-# GND
-# GND
-=== J8 - 8-bit I/O connector ===
+* Solder center pin with big solder blob
+** A bit too high for direct contact
+* Verify raised pad does not short to ground
-* FPGA Pins
+[[file:Atten_03_Solder CenterPads_720px.jpg]]
-# 3.3V
+* Solder side resistor(s)
-# 3.3V
+* Leave room for center resistor(s)
-# 48
-# 47
-# 52
-# 51
-# 58
-# 55
-# 76
-# 69
-# GND
-# GND
-== Schematics ==
+[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
-* [http://land-boards.com/EP2C5-DB/EP2C5-DB_Schematic_Rev_X5.pdf Rev X5 schematic]
+* Measure side resistors from pad to ground
-* [http://land-boards.com/EP2C5-DB/EP2C5-DB_Schematic_Rev_X6.pdf Rev X6 schematic]
+* Should match value
+* Solder center resistor(s)
-== Multicomp Builds ==
+[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
-* [https://github.com/douggilliland/MultiComp/tree/master/MultiComp_On_EP2C5 Github repository for Multicomp builds]
+* Verify no shorts between centers and ground
-== Programming the Flash PROM Memory ==
+== References ==
-=== Permanent (.pof file) ===
+<video type="youtube">A5gGeV7CiQ0</video>
-[[File:Program-permanent-720px.png]]
-=== Temporary (.sof file) ===
-[[File:Program-temporarily-720px.png]]
-== Pin List (Multicomp) ==
-<pre>
-# Clocks and reset
-set_location_assignment PIN_17 -to clk
-set_location_assignment PIN_144 -to n_reset
-set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to n_reset
-# PS/2
-set_location_assignment PIN_87 -to ps2Data
-set_location_assignment PIN_86 -to ps2Clk
-# ACIA (Serial)
-set_location_assignment PIN_60 -to serSelect
-set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to serSelect
-set_location_assignment PIN_104 -to urts1
-set_location_assignment PIN_101 -to urxd1
-set_location_assignment PIN_103 -to utxd1
-# External SRAM
-set_location_assignment PIN_4 -to n_sRamWE
-set_location_assignment PIN_126 -to n_sRamCS
-set_location_assignment PIN_134 -to n_sRamOE
-set_location_assignment PIN_32 -to sramAddress[16]
-set_location_assignment PIN_8 -to sramAddress[15]
-set_location_assignment PIN_30 -to sramAddress[14]
-set_location_assignment PIN_24 -to sramAddress[13]
-set_location_assignment PIN_28 -to sramAddress[12]
-set_location_assignment PIN_136 -to sramAddress[11]
-set_location_assignment PIN_132 -to sramAddress[10]
-set_location_assignment PIN_139 -to sramAddress[9]
-set_location_assignment PIN_142 -to sramAddress[8]
-set_location_assignment PIN_143 -to sramAddress[7]
-set_location_assignment PIN_141 -to sramAddress[6]
-set_location_assignment PIN_137 -to sramAddress[5]
-set_location_assignment PIN_133 -to sramAddress[3]
-set_location_assignment PIN_135 -to sramAddress[4]
-set_location_assignment PIN_129 -to sramAddress[2]
-set_location_assignment PIN_125 -to sramAddress[1]
-set_location_assignment PIN_121 -to sramAddress[0]
-set_location_assignment PIN_122 -to sramData[7]
-set_location_assignment PIN_120 -to sramData[6]
-set_location_assignment PIN_118 -to sramData[5]
-set_location_assignment PIN_114 -to sramData[4]
-set_location_assignment PIN_112 -to sramData[3]
-set_location_assignment PIN_113 -to sramData[2]
-set_location_assignment PIN_115 -to sramData[1]
-set_location_assignment PIN_119 -to sramData[0]
-# Composite Video
-set_location_assignment PIN_75 -to video
-set_location_assignment PIN_74 -to videoSync
-# VGA
-set_location_assignment PIN_64 -to videoB0
-set_location_assignment PIN_63 -to videoB1
-set_location_assignment PIN_67 -to videoG0
-set_location_assignment PIN_65 -to videoG1
-set_location_assignment PIN_70 -to videoR0
-set_location_assignment PIN_69 -to videoR1
-set_location_assignment PIN_71 -to hSync
-set_location_assignment PIN_72 -to vSync
-# J6 IO
-set_location_assignment PIN_25 -to J6IO8[0]
-set_location_assignment PIN_31 -to J6IO8[1]
-set_location_assignment PIN_41 -to J6IO8[2]
-set_location_assignment PIN_40 -to J6IO8[3]
-set_location_assignment PIN_43 -to J6IO8[4]
-set_location_assignment PIN_42 -to J6IO8[5]
-set_location_assignment PIN_45 -to J6IO8[6]
-set_location_assignment PIN_44 -to J6IO8[7]
-# J8 I/O
-set_location_assignment PIN_48 -to J8IO8[0]
-set_location_assignment PIN_47 -to J8IO8[1]
-set_location_assignment PIN_52 -to J8IO8[2]
-set_location_assignment PIN_51 -to J8IO8[3]
-set_location_assignment PIN_58 -to J8IO8[4]
-set_location_assignment PIN_55 -to J8IO8[5]
-</pre>
-== EP2C5-DB Assembly Sheet ==
-* [[EP2C5-DB Rev X6 Assembly Sheet]]
-* [[EP2C5-DB-TH Rev 1 Assembly Sheet]]