Difference between pages "TinySA" and "RF Attenuators"

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[[file:tinySA.jpg]]
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== Homebrew RF Attenuators ==
  
== TinySA - Spectrum Analyzer - Specifications ==
+
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
  
=== User interface ===
+
== Attenuators ==
 +
 
 +
[[file:Chart_mW_vs_dbM.PNG]]
 +
 
 +
=== 30 dB Attenuator ===
 +
 
 +
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
  
* Display resolution 320*240 pixels
+
[[file:Atten30dB_P116-720px.jpg]]
* Screen diagonal 2.8"
 
* 16 bits per RGB pixels
 
* Resistive touch control
 
* Jog switch control
 
* USB serial port control
 
* Optional TTL USART port (SW not yet implemented) on the internal PCB
 
* Linear power supply to avoid switching noise.
 
  
The input/output specification of the tinySA is split over the 4 modes
+
[[file:30dB_Attenuator.PNG]]
  
=== Low input mode spec ===
+
* 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)
  
* Input frequency range from 100kHz to 350MHz
+
* NanoVNA scan data
* Input impedance 50 ohm when input attenuation set to 10dB or more.
 
* Selectable manual and automatic input attenuation between 0dB and 31dB in 1 dB steps
 
* Absolute maximum input level without attenuation of +10dBm
 
* Absolute maximum input power with 30dB attenuation of +20dBm for short period
 
* Input Intercept Point of third order modulation products (IIP3) with 0dB attenuation of +15dBm
 
* 1dB compression point at +2dBm with 0dB attenuation
 
* Power detector resolution of 0.5dB and linearity versus frequency of +/-1dB
 
* Absolute power level accuracy after power level calibration of +/- 1dB
 
* Lowest discernible signal using a resolution bandwidth of 30kHz of -102dBm
 
* Frequency accuracy equal to the selected resolution bandwidth
 
* Phase noise of -90dB/Hz at 100kHz offset and -115dB/Hz at 1MHz offset
 
* Spur free dynamic range when using a 30kHz resolution bandwidth of 70dB
 
* Manually selectable resolution filters of 3, 10, 30, 100, 300, 600kHz. Automatic selection of one of the 57 resolution filters.
 
* On screen resolution of 145 or 290 measurement points.
 
* Scanning speed of over 1000 points/second using largest resolution filters.
 
* Automatic optimization of actual scanning points to ensure coverage of the whole scan range regardless of the chosen resolution bandwidth
 
* Spur suppression option for assessing if certain signals are internally generated or actually present in the input signal
 
  
=== High input mode spec ===
+
[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
  
* Input frequency range from 240MHz to 960MHz
+
[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
* As there is no input bandfilter strong signals outside the 240MHz to 960MHz range can cause distortion of the in band signals
 
* Absolute maximum input level without attenuation of +10dBm
 
* Input Intercept Point of third order modulation products (IIP3) of -5dBm
 
* 1dB compression point at -6dBm with 0dB attenuation
 
* Power detector resolution of 0.5dB and linearity versus frequency of +/-1dB
 
* Absolute power level accuracy after power level calibration of +/- 1dB
 
* Lowest discernible signal using a resolution bandwidth of 30kHz of -115dBm
 
* Frequency accuracy equal to the selected resolution bandwidth
 
* Spur free dynamic range when using a 30kHz resolution bandwidth of 50dB
 
* Selectable (automatic and manual) resolution filters of 3, 10, 30, 100, 300 and 600kHz
 
* Optional 25dB to 40dB frequency dependent input attenuator. The power level error with this attenuator activated increases to +/- 15dB
 
* On screen resolution of 145 or 290 measurement points.
 
* Scanning speed of over 1000 points/second using largest resolution filters.
 
* Automatic optimization of actual scanning points to ensure coverage of the whole scan range regardless of the chosen resolution bandwidth
 
  
=== Low output mode spec ===
+
* LTSPICE Simulation
  
* Sinus output with harmonics below -40dB of fundamental
+
[[file:LTSPice_30dB.PNG]]
* Output frequency range from 100kHz to 350MHz
 
* Output level selectable in 1dB steps between -76dBm and -6dBm
 
* Optional AM, narrow FM and wide FM modulation or slow sweep over selectable frequency span
 
  
=== High output mode spec ===
+
=== 20 dB Attenuator ===
  
* Square wave output
+
[[file:Atten_20dB_P115-720px.jpg]]
* Output frequency range from 240MHz to 960MHz
 
* Output level selectable in variable increments between -38dBm and +13dBm
 
* Optional narrow FM and wide FM modulation or slow sweep over selectable frequency span
 
  
=== Reference generator spec ===
+
[[file:20dB_Attenuator.PNG]]
  
* Optional square wave output with fundamental at -25dBm connected to high input/output
+
* Build
* Frequency can be set to 1MHz, 2MHz, 4MHz, 10MHz, 15MHz or 30MHz.
+
** 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)
  
=== Battery spec ===
+
[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
  
* Charging time max 1 hour on 500mA minimum USB port or USB charger
+
[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
* Operation on fully charged battery for at least 2 hours
 
* Maximum input level
 
** 0 dBm = 1 mW
 
** dBm = 10*LOG(milliwatts)
 
** -10 dBm = 0.1 mW
 
** +10dBm = 10 mW
 
** +20dBm = 1000 mW
 
* 3.3V at 50 Ohm = 0.2178W
 
** 217.8 mW = 23.4 dBm
 
  
== Attenuators ==
+
* 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]]
  
* [[RF Attenuators|Homebrew RF Attenuators]]
+
[[file:10dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
  
== References ==
+
* LTSPICE Simulation
  
* [https://www.tinysa.org/wiki/ tinySA wiki]
+
[[file:LTSPice_10dB.PNG]]
* [http://athome.kaashoek.com/tinySA/Windows/ tinySA-App Software]
 
* [https://store2.rlham.com/shop/catalog/product_info.php?products_id=75243&osCsid=adsqkp0uum898eahocj1marc43 R&L page]
 
  
== Measurements ==
+
=== Attenuator Construction ===
  
=== No Stimulus ===
+
* 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
  
* 50 Ohm terminator on Low port
+
[[file:Atten_01_SMAs_720px.jpg]]
  
[[file:Tiny-SA App v1.1.19.20.PNG]]
+
* Cut "T" Shaped pads
 +
** I used nibbler
 +
* Center fits between connector ground pins
 +
* Glue down pads with Superglue
  
=== VFO-001 ===
+
[[file:Atten_02_Pads_720px.jpg]]
  
[[File:VFO-001_P132-720px.jpg]]
+
* Solder center pin with big solder blob
 +
** A bit too high for direct contact
 +
* Verify raised pad does not short to ground
  
* [[VFO-001]]
+
[[file:Atten_03_Solder CenterPads_720px.jpg]]
* Set to 20 MHz
 
* 3.3V square wave drive
 
* Rich odd harmonic content
 
* Lots of other noise
 
* Using 20 dB attenuator (from above)
 
* 1-301 MHz
 
  
[[file:VFO-002_20dB_001.PNG]]
+
* Solder side resistor(s)
 +
* Leave room for center resistor(s)
  
== Videos ==
+
[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
  
<video type="youtube">n6WEM3--Npc</video>
+
* Measure side resistors from pad to ground
 +
* Should match value
 +
* Solder center resistor(s)
  
<video type="youtube">Sdb_cs13njk</video>
+
[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
  
<video type="youtube">qxH0CQOf2NM</video>
+
* Verify no shorts between centers and ground

Revision as of 11:47, 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