SSB6 Design

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SSB6 P1916-720px.jpg

Design[edit]

  • 6 element filter
  • W7ZOI Crystal Filter paper has several crystal filter designs
    • Narrow bandwidth bandpass filters for CW/SSB
    • This is the 6 crystal SSB6
  • Used for transmit/receive
  • 9 MHz nominal frequency
  • 50 Ohms in/out impedance
  • Bin crystals using Colpitts Crystal Oscillator
    • Hand select close values from a pile of crystals
    • Can get much closer than 10% of bandwidth with 50 crystals
  • W7ZOI Filters on Kits and Parts Boards
    • Other filter builds
    • 5 or less crystals

W7ZOI SSB6 Schematic[edit]

XTAL-SSB-6Crystals.PNG

  • Response curve

W7ZOI SSB6 Curve.PNG

Build[edit]

FT37-43 10 turns 9MHz.PNG

Schematic[edit]

SSB6 SCHEMATIC.PNG

Dishal Values[edit]

  • Impedance = 195.9
RefDes Dishal  RefDes W7ZOI
Ck12   87.3    C3/C9  82
Ck23   110.9   C4/C8  100
Ck34   114.4   C6     100
Cs1    110     C2/C10 120
Cs3    369.5   C5/C7  470

Dishal-sim-01.PNG

Measured Crystal Values[edit]

  • 6 crystals within 7 Hz of each other
    • Selected from 50 purchased
Number Freq        Delta from average
09     8.997791    -7.7
12     8.997791    -7.7
41     8.997793    -5.7
06     8.997794    -4.7
21     8.997798    -0.7
38     8.997798    -0.7

Enclosure 80x50x20[edit]

  • Fits in 80x50 extruded enclosure
  • Material: Aluminum
  • Color: black
  • Size: approx.80*50*20mm
  • Thickness: approx.1mm

Enclosure-80x50x20.jpg

Performance Measurements[edit]

Overall[edit]

  • NanoVNA
  • 2.5 KHz / div
  • Initial measurement shows issues (solved later on this page)

SSB6 NanoVNA 9MHz 2.5KHzPerDiv.png

Detailed[edit]

  • 1 KHz/div
  • Bandpass looks about 2500 KHz = good
    • Left freq = 8.99762 MHz
    • Right freq = 9.00005 MHz
    • Delta = 2.43 KHz
    • Center frequency = 8.99885 MHz
      • Implies crystals are properly matched?
  • Insertion loss at "best" point (red marker) -5.14 dB = OK
  • Deep skirts = good
  • Ripple looks bad
  • Right side low

SSB6 NanoVNA 9MHz 1KHzPerDiv.png

Compared to SSB4[edit]

  • Fcenter = 8.998MHz
  • Span = 10KHz
  • 1 KHz/div
  • Skirts much deeper on SSB6 than SSB4
    • -90 dB on SSB6 at window edges
    • -60 dB on SSB4 at window edges
  • Passband much flatter on SSB4
  • Insertion loss lower on SSB4
  • SSB4

SSB4 vsS SB6 NanoVNA 9MHz 1KHzPerDiv.png

Improvements[edit]

  • Investigate changes to remove ripple and clean up right side of passband

Clean Board[edit]

  • Cleaned board
  • Removed wires on transformer that were not clipped flush-ish
    • No effect - same ripple, same drop at the right side, same insertion loss
  • No change

SB6 NanoVNA 9MHz 1KHzPerDiv Added Grounds.png

Add grounds to cases of crystals[edit]

  • Had to scrape away solder mask to solder
    • Through hole vias were plated through
    • Would be better with ground pads with cleared solder mask and thermal relief (Version 2)
  • No change

SSB6 P1889 Soldered-Grounded Cases 720PX.jpg

Incremental Build and Test[edit]

  • Start with unpopulated board
  • Add SMA connectors

SSB6 P1887 Test 01 SMAs-Installed 720PX.jpg

  • Added transformers
  • Installed 200 ohm resistors at input caps to ground
    • At C1, C11

SSB6 P1891 tEST 02 TRANSFORMER TEST.JPG

  • Measure transformer impedances from NanoVNA
    • Input
      • 48.9-j0.900 Ohms
      • VSWR 1:1.031
    • Output
      • 48.7-j0.714 Ohms
      • VSWR 1:1.031
  • Impedance is flat over passband
  • Transformer working as expected

SSB6 NanoVNA 9MHz Transformer Input Impedance.png

  • 1-30 MHz scan
  • Toroid flat to board or tilted up = same performance
  • Not flat over band, but OK at 9 MHz

SSB6 NanoVNA 1-30MHz Transformer Input Impedancee.png

  • Add machine socket pins to install parts

SSB6 P1892-720px.jpg

  • Install caps in socket pins
08	8.997809	10.3	10.3	
30	8.997810	11.3	11.3	
48	8.997812	13.3	13.3	
50	8.997814	15.3	15.3	
31	8.997818	19.3	19.3	
46	8.997822	23.3	23.3
  • Parts installed on pinned card

PinJig-01.png

Fixed First Card[edit]

  • Compared pinned board to first board
  • Noted C5 and C6 were swapped
  • Repaired
  • Sweep

PinJig-02.png

  • Excellent results
  • 2.625KHz bandwidth - close to 2.5KHz design goal
  • 2.5 dB insertion loss
  • Low ripple.
  • Fcenter = 8.998892 MHz

PinJig-03.png

SSB4 vs SSB6[edit]

SSB4 vsS SB6 NanoVNA 9MHz 1KHzPerDiv-fixed.png

  • Input complex impedance across passband

ile:SSB6_Input Impedance_InPassband.png

References[edit]

Sorted crystals table[edit]

Assembly Sheet[edit]