Difference between pages "Serial Terminal" 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 "Serial Terminal" 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: @@
-== Display Processor ==
+== Homebrew RF Attenuators ==
-This is an inexpensive and small serial terminal design. This design can drive 80x25 text and graphics displays. This design is based on Grant Searle's Monitor and keyboard controllers. This design has been implemented on two cards, this card and Serial I/O Processor - which is the other half of this terminal.
+[[file:Atten_30dB_20dV_P1812-720px.jpg]]
-Here's Grant's schematic:
+== Attenuators ==
-Searle-DisplayProc.gif
+[[file:Chart_mW_vs_dbM.PNG]]
-* Video controller specification
+=== 30 dB Attenuator ===
-* Very easy to interface to, fast and requires no host/external memory
-* Character set
-* Full "CGA" (8x8) character definitions as used on the IBM PC (DOS).
-* Screen size
-** Text - 80x25, 40x25, 80x12, 40x12, Graphics 160x100 or ANY mix (defined per 1 of 25 rows)
-* Resolution
-** 640x200 for 80 char text
-** 160x100 for graphics
-* Fonts
-** Font sizes are defined for each line
-** All chars on the same line have the same font size and style
-* Graphics
-** Any part of the active screen, up to 160x100 pixels
-** Each pixel individually addressable
-** Defined on any of the 25 screen lines
-* Video output
-** Standard composite monochrome video
-** PAL or NTSC timing
-** Non-interlaced so no flicker
-* Display memory
-** 2000 chars internal + 25 line attributes - no host memory needed
-** Very fast update and scrolling whichever interface is used
-* Interface
-** 8 bit data bus (requires 10 I/O pins)
-** 4 bit data bus (requires 6 I/O pins)
-* two-wire (I2C) uses only 2 pins
-** I2C (thanks to Dave Curran for his guidance and code on this) supports low (100KHz) and high (400KHz) speed clocks or higher (1MHz or more easily achievable).
-* Hardware
-** Very low cost - two chips - ATmega328 and 74HCT166 (Shift Register)
-* Connectors
-** J1 - Video Connector
-** RCA Jack
-** Center is signal
-** Outside is ground
-== P1 - Card Interconnect ==
+* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
-* 2x8 header, 0.1" pitch
-*Pinout
-# VCC
-# VCC
-# ID0
-# ID1
-# ID2 - MOSI for ISP Download cable
-# ID3 - MISO for ISP Download cable
-# ID4 - SCK for ISP Download cable
-# ID5
-# ID6
-# ID7
-# Unused
-# RESET*
-# ACK/SDA (R4 terminator for I2C interface)
-# AVAIL/SCL (R3 terminator for I2C interface)
-# GND
-# GND
-=== ISP Cable ===
+[[file:Atten30dB_P116-720px.jpg]]
-P1 Pin	Description	ISP Pin	Description	Color
+[[file:30dB_Attenuator.PNG]]
-	VCC	2	VCC	Red
-
-
-
-	MOSI	4	MOSI	Green
-	MISO	1	MISO	Grey
-	SCK	3	SCK	Yellow
-
-
-
-
-	RESET	5	RST	White
-
-
-	GND	6	GND	Black
-
-Configuration Resistors
-Configuration Resistor values can also be set through soft switches in the code
-R5 - Two-wire interface (I2C)
-R6 - 4-bit interface
-R7 - 10K for NTSC, open for PAL
-R3, R4 - I2C Termination resistors - Install for I2C termination - typical = 2.2K
-Software
-Source Code
-Copy of the Display Processor Code in my GitHub Repository - any changes are here
-Atmel AVR Studio Download
-In
-C:\Program Files (x86)\Arduino\hardware\tools\avr\bin
-Type
-avrdude -U lfuse:w:0xc6:m -U hfuse:w:0xd9:m -e -F -v -patmega328p -carduino -PCOM8 -b19200 -D -Uflash:w:"C:\Users\doug_000\Documents\GitHub\lb-Arduino-Code\LBCards\DisplayProc\AssemblerApplication1\AssemblerApplication1\Debug\AssemblerApplication1.hex":i -C"C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf"
-Checkout
-Saw a blinking cursor
-Assembly Sheet
-Display Processor Assembly Sheet
-SIOPROC-01-640px.jpg
+* 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)
-Contents
+* NanoVNA scan data
-	Serial I/O Processor
-	Features
-	Connectors
-.1	P1 - Card Interconnect
-.2	P2 - PS/2 Keyboard
-.2.1	PS/2 Adapter Cable
-.3	P3 - 5V FTDI/Power Connector
-.4	P4 - In-System Programmer (ISP) Connector
-	Configuration Resistors
-	Software
-	Rev X1 Issues
-	Assembly Sheet
-Serial I/O Processor
-This is an inexpensive and small serial terminal design. This design can drive 80x25 text and graphics displays. This design is based on Grant Searle's Monitor and keyboard controllers. This design has been implemented on two cards, this card and Display Processor - which is the other half of this terminal.
-Here's Grant's schematic:
+[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
-Searle-SIOProc.gif
+[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
-Features
+* LTSPICE Simulation
-Serial interface
-Fully buffered 115200 baud, handshake on receive, TTL levels.
-Keyboard interface
-PC PS/2 standard keyboard connector, accepts standard keyboards made for PCs. Keyboard LED illumination implemented, and allows for caps lock and num lock.
-Hardware
-Two cards
--bit interface connector for card-to-card connections
-Connectors
-P1 - Card Interconnect
-x8 header, 0.1" pitch
-Connector matches the pinout of the other card so it can be mated directly to the other card via 1:1 cable or a female header on this card
-Pinout
-VCC
-VCC
-ID0
-ID1 - CS* for ISP Download cable
-ID2 - MOSI for ISP Download cable
-ID3 - MISO for ISP Download cable
-ID4 - SCK for ISP Download cable
-ID5
-ID6
-ID7
-Unused
-RESET*
-ACK/SDA (R4 terminator for I2C interface)
-AVAIL/SCL (R3 terminator for I2C interface)
-GND
-GND
-P2 - PS/2 Keyboard
-PS2Conn.png
-x4 header, 0.1" pitch
+[[file:LTSPice_30dB.PNG]]
-GND
-VCC
-KBCLK
-KBDAT
-PS/2 Adapter Cable
-S-l1600-Adapter-Cable-720px.jpg
-Ordered this cable from ebay.
+=== 20 dB Attenuator ===
-Replaced 5 pin connector with 4 pin 0.1" pitch "Dupont" connector
-Pinout of cable after re-wiring with new connector
-PS/2 Pin	P2 Pin	Description	Color
-	4	Data	TBD
-	N/C	N/C	N/A
-	1	GND	TBD
-	2	+5V	TBD
-	3	Clk	TBD
-	N/C	N/C	N/A
-P3 - 5V FTDI/Power Connector
-S-l1600.jpg
-x6 header, 0.1" pitch
+[[file:Atten_20dB_P115-720px.jpg]]
-Pinout
-GND
+[[file:20dB_Attenuator.PNG]]
-RTS
-VCC (+5V)
+* Build
-TX
+** Standard 5% resistor values
-RX
+** R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
-N/C
+** R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
-P4 - In-System Programmer (ISP) Connector
+** Flat from 0-30 MHz
-Cable for use with ArduinoISP programmer
+** Measured attenuation is flat
-.1" pitch "Dupont" connector
+** Input Impedance - tbd ohms, tbd nF
-x3
+** SWR tbd
-MISO
+** 1W max (8.6 V max, 0 ohm source)
-VCC
-SCK
+[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
-MOSI
-RESET*
+[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
-GND
-Configuration Resistors
+* LTSPICE Simulation
-Configuration Resistor values can also be set through soft switches in the code
-R1, R2 - I2C termination - install to terminate - typically 2.2K
+[[file:LTSPice_20dB.PNG]]
-R5 - Two Wire Interface output (I2C)
-R6 - 4-bit Interface
+=== 10 dB Attenuator ===
-Software
-Source Code
+[[file:Atten_10dB_P115-720px.jpg]]
-Copy of the Serial I/O Processing Code in my GitHub Repository - any changes are located here
-Atmel AVR Studio Download
+[[file:10dB_Attenuator.PNG]]
-avrdude -U lfuse:w:0xc6:m -U hfuse:w:0xd9:m -e -F -v -patmega328p -carduino -PCOM8 -b19200 -D -Uflash:w:"C:\Users\doug_000\Documents\GitHub\lb-Arduino-Code\LBCards\SIOProc\GccApplication1\GccApplication1\Debug\GccApplication1.hex":i -C"C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf"
-Rev X1 Issues
+* Build
-FTDI handshake moved from P3-6 to pin P3-2
+** Standard 5% resistor values
-Cut etch at FTDI connector P3-6
+** R1 = 2 of 150 in parallel also in parallel with 1.5K = 71.43 ohms (0.3% error)
-Add wire U1-26 to P3-2
+** R2 = 3 of 330 Ohm 1/4W parallel resistors paralleled with 810 ohms = 96.85 ohms (0.62% error)
-Assembly Sheet
+** Flat from 0-30 MHz
-SIOProc-01 Assembly Sheet
+** 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
+[[file:LTSPice_10dB.PNG]]
+=== 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
+[[file:Atten_01_SMAs_720px.jpg]]
+* Cut "T" Shaped pads
+** I used nibbler
+* Center fits between connector ground pins
+* Glue down pads with Superglue
+[[file:Atten_02_Pads_720px.jpg]]
+* Solder center pin with big solder blob
+** A bit too high for direct contact
+* Verify raised pad does not short to ground
+[[file:Atten_03_Solder CenterPads_720px.jpg]]
+* Solder side resistor(s)
+* Leave room for center resistor(s)
+[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
+* Measure side resistors from pad to ground
+* Should match value
+* Solder center resistor(s)
+[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
+* Verify no shorts between centers and ground
+== References ==
+<video type="youtube">A5gGeV7CiQ0</video>