Difference between pages "RPI-I2C-HUB" and "RF Attenuators"

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[[File:tindie-mediums.png|link=https://www.tindie.com/products/land_boards/i2c-multiplexer-for-the-raspberry-pi-rpi-i2c-hub/]]
+
== Homebrew RF Attenuators ==
  
−
<video type="youtube">R_YUetR83N4</video>
+
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
  
−
== I2C Hub for the Raspberry Pi ==
+
== Attenuators ==
  
−
[[File:I2C-RPT-01_-6026_CCA-640px.jpg]]
+
[[file:Chart_mW_vs_dbM.PNG]]
  
−
== Features ==
+
=== 30 dB Attenuator ===
  
−
* I2C Hub / Repeater / Replicator / Multiplexer / De-multiplexer
+
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
−
** PCA9544A IC
 
−
* Controlled via I2C
 
−
* Multiple part vendors
 
−
* Devices with the same address can be attached to different ports
 
−
* Host I2 port goes to Raspberry Pi I2C lines
 
−
* 3.3V host operation
 
−
* Four I2C slave ports
 
−
* I2C ports can use the Raspberry Pi or have their own power (power source select jumper)
 
−
* A Raspberry PI which runs 3.3V can control an I2C device which runs at 5V
 
−
* Voltage translation between the ports
 
−
* I2C ports can be 3.3V or 5V
 
−
* Fits in any Raspberry Pi model
 
−
* Cutout for Model B RCA video jack
 
−
* Interrupt controller on each channel and host 100KHz/400KHz operation
 
−
* On-board termination resistors
 
  
−
== Example Code/Driver ==
+
[[file:Atten30dB_P116-720px.jpg]]
  
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* [https://github.com/land-boards/RasPi/tree/master/RPI-I2C-Hub Git Hub Repo]
+
[[file:30dB_Attenuator.PNG]]
  
−
== Assembly Sheet ==
+
* 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)
  
−
* [[RPI-I2C-HUB Assembly Sheet]]
+
* NanoVNA scan data
 +
 
 +
[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
 +
 
 +
[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
 +
 
 +
* LTSPICE Simulation
 +
 
 +
[[file:LTSPice_30dB.PNG]]
 +
 
 +
=== 20 dB Attenuator ===
 +
 
 +
[[file:Atten_20dB_P115-720px.jpg]]
 +
 
 +
[[file:20dB_Attenuator.PNG]]
 +
 
 +
* 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:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
 +
 
 +
[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
 +
 
 +
* LTSPICE Simulation
 +
 
 +
[[file:LTSPice_20dB.PNG]]
 +
 
 +
=== 10 dB Attenuator ===
 +
 
 +
[[file:Atten_10dB_P115-720px.jpg]]
 +
 
 +
[[file:10dB_Attenuator.PNG]]
 +
 
 +
* 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
 +
 
 +
[[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>

Revision as of 11:50, 7 September 2021

Homebrew RF Attenuators

Atten 30dB 20dV P1812-720px.jpg

Attenuators

Chart mW vs dbM.PNG

30 dB Attenuator

Atten30dB P116-720px.jpg

30dB Attenuator.PNG

  • 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

30dB Attenuator NanoVNA Setup Curve 900MHz.PNG

30dB Attenuator NanoVNA Data 900MHz.PNG

  • LTSPICE Simulation

LTSPice 30dB.PNG

20 dB Attenuator

Atten 20dB P115-720px.jpg

20dB Attenuator.PNG

  • 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)

20dB Attenuator NanoVNA Setup Curve 900MHz.PNG

20dB Attenuator NanoVNA Data 900MHz.PNG

  • LTSPICE Simulation

LTSPice 20dB.PNG

10 dB Attenuator

File:Atten 10dB P115-720px.jpg

10dB Attenuator.PNG

  • 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

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

Atten 01 SMAs 720px.jpg

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

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

Atten 03 Solder CenterPads 720px.jpg

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

Atten 04 Solder Side Resistors 720px.jpg

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

Atten 05 Solder Center Resistors 720px.jpg

  • Verify no shorts between centers and ground

References

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