Difference between revisions of "RF Attenuators"

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[[file:Atten_30dB_20dV_P1812-720px.jpg]]
 
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
  
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=== 30 dB Attenuator ===
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[[Homebrew RF Attenuators]]
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* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
 
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[[file:Atten30dB_P116-720px.jpg]]
 
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[[file:30dB_Attenuator.PNG]]
 
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* Built
 
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** Standard 5% resistor values
 
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** R1 = 820 in parallel with 22K = 790.6 ohms
 
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** R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
 
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** Flat from 0-30 MHz
 
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** Measured attenuation is flat
 
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*** -30.01dB at 1 MHz
 
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*** -30.24dB at 30 MHz
 
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** Input Impedance - 53.1 ohms, 21.3nF
 
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** SWR 1.06
 
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** 1/2W max (5VDC max, 0 ohm source)
 
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* NanoVNA scan data
 
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[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
 
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[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
 
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* LTSPICE Simulation
 
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[[file:LTSPice_30dB.PNG]]
 
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=== 20 dB Attenuator ===
 
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[[file:Atten_20dB_P115-720px.jpg]]
 
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[[file:20dB_Attenuator.PNG]]
 
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* Build
 
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** Standard 5% resistor values
 
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** R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
 
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** R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
 
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** Flat from 0-30 MHz
 
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** Measured attenuation is flat
 
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** Input Impedance - tbd ohms, tbd nF
 
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** SWR tbd
 
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** 1W max (8.6 V max, 0 ohm source)
 
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[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
 
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[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
 
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* LTSPICE Simulation
 
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[[file:LTSPice_20dB.PNG]]
 
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=== Attenuator Construction ===
 
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* Single side copper clad PCB
 
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** Approx 2"x1"
 
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* Clean with steel wool
 
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* Solder SMA connectors
 
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** Use large alligator clips to hold while soldering
 
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** Solder on sides only
 
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[[file:Atten_01_SMAs_720px.jpg]]
 
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* Cut "T" Shaped pads
 
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** I used nibbler
 
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* Center fits between connector ground pins
 
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* Glue down pads with Superglue
 
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[[file:Atten_02_Pads_720px.jpg]]
 
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* Solder center pin with big solder blob
 
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** A bit too high for direct contact
 
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* Verify raised pad does not short to ground
 
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[[file:Atten_03_Solder CenterPads_720px.jpg]]
 
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* Solder side resistor(s)
 
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* Leave room for center resistor(s)
 
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[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
 
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* Measure side resistors from pad to ground
 
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* Should match value
 
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* Solder center resistor(s)
 
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[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
 
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* Verify no shorts between centers and ground
 
  
 
== Attenuator Design - Rev 2 ==
 
== Attenuator Design - Rev 2 ==

Latest revision as of 12:08, 25 November 2021

Purchased Attenuators

Programmable Attenuator

PE4302 P1833-720px.jpg

Triple Attenuator

ATTEN4 CHINA PCB.PNG

Homebrew RF Attenuators

Atten 30dB 20dV P1812-720px.jpg

Homebrew RF Attenuators

Attenuator Design - Rev 2

ATTEN1 P1896-720PX.jpg

  • 6 dB resistor values in above
  • OshPark clear soldermask "After Dark"
    • $4.40 for 6 cards
  • Small/light enough to hang directly off fragile devices
  • SMA connectors
    • Male/female are good choices for direct connect to devices
  • Resistors
    • 1206
      • 1/4W
      • 1% values get good accuracy (approx. 2%) even though not exact to calculated values
  • Good bandwidth up well past RF

10dB Attenuator.PNG

Parts

Mfr. # Manufacturer Customer # Qty R1/R2 Description
RK73H2BTTE17R8F KOA Speer ATTEN_03DB 1 R1 Resistors - SMD 1/4W 17.8 ohms 1%
RC1206FR-07294RL YAGEO ATTEN_03DB 2 R2 Resistors - SMD 294 ohms 1/4W 1206 1%
RK73H2BTTD37R4F KOA Speer ATTEN_06DB 1 R1 Resistors - SMD 1/4W 37.4 ohms 1%
CRCW1206150RFKEAC Vishay ATTEN_06DB 2 R2 Resistors - SMD 1/4Watt 150 ohms 1%
RC1206FR-0771R5L YAGEO ATTEN_10DB 1 R1 Resistors - SMD 71.5 ohms 1/4W 1206 1%
RC1206FR-0797R6L YAGEO ATTEN_10DB 2 R2 Resistors - SMD 97.6 ohms 1/4W 1206 1%
RK73H2BTTD1070F KOA Speer ATTEN_13DB 1 R1 Resistors - SMD 1/4W 107 ohms 1%
RC1206FR-0778R7L YAGEO ATTEN_13DB 2 R2 Resistors - SMD 78.7 ohms 1/4W 1206 1%
AC1206FR-07249RL YAGEO ATTEN_20DB 1 R1 Resistors - SMD 249 ohms 1/4W 1206 1%
RK73H2BTTDD61R9F KOA Speer ATTEN_20DB 2 R2 Resistors - SMD 61.9 ohms 1%
RK73H2BTTD7870F KOA Speer ATTEN_30DB 1 R1 Resistors - SMD 1/4W 787 ohms 1%
AC1206FR-0753R6L YAGEO ATTEN_30DB 2 R2 Resistors - SMD 53.6 ohms 1/4W 1206 1%
RC1206FR-072K49L YAGEO ATTEN_40DB 1 R1 Resistors - SMD 2.49k ohms 1/4W 1206 1%
RK73H2BTTD51R0F KOA Speer ATTEN_40DB 2 R2 Resistors - SMD 1/4W 51 ohms 1%
RK73H2BTTDD49R9F KOA Speer ATTEN_50_60DB 2 R2 Resistors - SMD 49.9 ohms 1%
RC1206FR-077K87L YAGEO ATTEN_50DB 1 R1 Resistors - SMD 7.87k ohms 1/4W 1206 1%
RC1206FR-0726K1L YAGEO ATTEN_60DB 2 R2 Resistors - SMD 26.1k ohms 1/4W 1206 1%

Measurements

  • NanoVNA
  • S21 gain
  • 1-900 MHz scan
  • Calibrated with cable on thru

6 dB Attenuator

  • Flat from 1-600 MHz
  • Higher attenuation past 600 MHz
  • S21

ATTEN1 NanoVNA 6dB S21 1-900MHz.png

  • S11 from 1-900 MHz

ATTEN1 NanoVNA 6dB S11 1-900MHz.png

40 dB Attenuator

  • Flat from 1-600 MHz
  • Higher attenuation past 600 MHz
  • -39.9 dB at 14 MHz
  • S21

ATTEN1 NanoVNA 40dB.png

  • Flat from 1-30 MHz
  • S21

ATTEN1 NanoVNA 40dB 1-30MHz.png

  • s11
  • 1-900 MHz

ATTEN1 NanoVNA 40dB S11 1-100MHz.png

  • VSWR
  • 1-900 MHz

ATTEN1 NanoVNA 40dB VSWR 1-100MHz.png

DC Block

  • Use same PCB
    • Install 0.1uF cap between the two SMAs
    • Leave off resistors to ground
  • Sweep 50 KHz to 900 MHz
  • S21 of -0.8 dB at 50 KHz
  • S21 of 0.44 dB at 900 MHz

ATTEN1 NanoVNA DC-BLOCK S21 50KHz-900MHz.png

  • Sweep 50 KHz to 900 MHz
  • S11

ATTEN1 NanoVNA DC-BLOCK S11 50KHz-900MHz.png

Attenuator Charts

DBm vs milliVolt milliWatts.PNG

DBm vs Volta Watts.PNG

DBm vs Volt Watts.PNG

References

  • Heavily inspired by Alan (W2AEW) video

W2AEW Attns-01.PNG

W2AEW Attns-02.PNG

W2AEW Attns-03.PNG

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