Difference between pages "MHS-5200A DDS Signal Generator" and "RF Attenuators"

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== Replace Wall-wart Power Supply ==
+
== Homebrew RF Attenuators ==
  
−
* Wall warts put AC on the ground.
+
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
−
** Fix it by replacing with an AC/DC linear supply
 
−
* '''Diodes backwards on silkscreen/image'''
 
  
−
[[File:MHS-5200A_PwrSupply.png]]
+
== Attenuators ==
  
−
=== Parts ===
+
[[file:Chart_mW_vs_dbM.PNG]]
  
−
* [https://www.mouser.com/ProductDetail/553-F14X POWER XFMR 6.3Vct@1.2A 115V CHASSIS MOUNT w/LEADS/F-14X ]
+
=== 30 dB Attenuator ===
−
* [https://www.mouser.com/ProductDetail/511-LF50ABV LF50ABV Voltage Regulator 5.0V 0.5A Positive]
 
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* 3x [https://www.mouser.com/ProductDetail/710-860020375018 Aluminum Electrolytic Capacitors - Radial Leaded WCAP-ATG5 1200uF 16V 20% Radial]
 
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* 4x [https://www.mouser.com/ProductDetail/583-1N5822-T 1N5822-T Schottky Diodes & Rectifiers Vr/40V Io/3A T/R]
 
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* 2x 5mm terminal blocks
 
  
−
=== Simulation ===
+
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
  
−
6.8Vrms = 9.615V peak
+
[[file:Atten30dB_P116-720px.jpg]]
  
−
[[File:SimResults-01.PNG]]
+
[[file:30dB_Attenuator.PNG]]
  
−
https://www.youtube.com/watch?v=TQXd7u4kPvs
+
* Built
−
https://www.youtube.com/watch?v=WfC0h8XhA4w
+
** 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
 +
 
 +
[[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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