Ham Salad


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Homebrew QRP Radio by NM0S, Ozarkcon 2010

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  • There may come a time when you don't have all the ingredients you need, or time to design, build and troubleshoot a homebrew rig, so it is perfectly fine to look for a kit to build. It's like when you are at work, craving the old ham salad, and you walk down to the vendamatic...
  • Introduction – dreamed of Heathkit, HW-8, Low-Power, simple, ‘trail-ready’. but bought FT-101. Bought HW-7 and learned shortcomings. Got into QRP, designed ‘yearly’ radio to match performance of ‘dream’ HW-8. Found many circuits and techniques from commercial and military radio gear not used by hams.
  • ‘Coconuts & Bamboo’ – ability to improvise from parts on hand, simple, forgiving design. Also a Hendricks kit
  • Trail ready – rugged – can you drop it like FT101?
  • Ultimate simple, but is it useable?
  • What I like of my favorite radio, and what I try to bring to those I design. As I design my project, I try to consider how easily it could be made into a kit, and assembled by someone else.
    Heathkit – well engineered. Design a radio to require minimum alignment. Robust design, tolerant of assembly, component imperfections.
  • Example Heathkit, used surplus components
    Milcomm gear, 50 lb batteries
    End goal – a transceiver that can be built by anyone, of parts available anywhere, that can be thrown into the trunk of a car without worry of damage.
    User fatigue, difference between toy and real radio, PLL/DDS tuning vs. knob
    ORIGINALITY – How many more NE602-LM386 radios de we need?
  • Rig was innovative, single control (tuning knob) Inserting plug to key jack switched in CW filter, ALC, AGC, Class-E, DSB. Ultra low power consumption.
  • Improvised heat sink – copper wire Class-E EER
  • No need for exotic RF transistors. Good to 30 MHz.
  • Using Class-E, the PA devices can be small, acting as effective mixers. Dan Tayloe, H-Mode
  • Also mixer
  • Much time and research has gone into the field of Radar – transmitting and receiving RF pulses – which is directly applicable to ham circuits
  • Requires 3:1 lowpass/highpass. Four, 50 Hz wide, Q=10 to 15. Provides 30 dB gain.
  • Ham Salad

    1. 1. ham salad Ozarkcon 2010 David Cripe NMØS Mount Vernon, Iowa QRP Radio Recipes
    2. 2. what are you hungry for? what do you have? HAM SALAD!
    3. 3. Why is my ham salad sandwich like QRP Radio? •You improvise from ingredients • you already have •There are few set rules •It can be made to fill a need •It can be messy •It doesn't have to be complicated •IT IS FUN TO MAKE!
    4. 4. How about store bought? There’s more than one definition of 'Homemade'!
    5. 5. It's OK to use a cookbook!
    6. 6. Radios I Like HW-8 - Heathkit
    7. 7. Radios I Like BitX-20 - Ashhar Farhan VU2ESE
    8. 8. Radios I Like PFR-3 – Hendricks / KD1JV
    9. 9. Radios I Like Pixie
    10. 10. Common Themes • Manufacturability – Repeatability – No SMT – Minimize toroids – Minimize alignment, test equipment • Common, classic components – Availability – No obsolescence – Often, better performance • Ergonomics – Minimum interface – Smart controls (AGC, ALC, switched plugs) – 'Eyes-off' feedback
    11. 11. Common Themes (cont'd) • Economy – Low-cost components – Long battery life • Operating Quality – Low audio noise, IMD – Useful tuning rate – Good filtering, no ringing. – Single-signal RX • Durability – Enclosure – Connectors – Circuit protections • BE ORIGINAL!
    12. 12. Projects from the NMØS kitchen: 2007 ARRL Homebrew Challenge
    13. 13. NMØS Projects NS-40 - No Simpler Transmitter
    14. 14. NMØS Projects Regenatron – High-performance Regenerative Receiver
    15. 15. NMØS Projects 2010 ARRL Homebrew Challenge NCA-40 - 'No Cheaper Amp'
    16. 16. NMØS Secret Ingredients •Class-E Power Amplifiers • Achieve >90% efficiency • 90% reduction in transistor heating • Improved VSWR Immunity • Simple 50% duty digital drive • High efficiency allows use of smaller final transistors, requiring less power to drive. • 2N7000 – 1W, IRF510 - 5W
    17. 17. NMØS Secret Ingredients •Class-E Power Amplifiers • Sample Waveforms
    18. 18. NMØS Secret Ingredients •Class-E Power Amplifiers References: ‘ClassE’, www.tonnesoftware.com/classe.html ‘Class-E AM Forum’, http://classe.monkeypuppet.com/ ‘Class-E Power Amplifiers for QRP’, QRP Quarterly, Summer 2009, p. 32
    19. 19. NMØS Secret Ingredients Use the PA as the front-end receive mixer (Also invented by Mike Rainey, AA1TJ) Drive is maintained on PA transistor gates DC bias is removed from PA drain choke • IF appears on PA drain • Very simple circuit • Good dynamic range • No T/R switching required.
    20. 20. NMØS Secret Ingredients Use the PA as the front-end receive mixer - to antenna
    21. 21. NMØS Secret Ingredients •Use 74HCxx Logic as RF Devices - • 74HC86 as a Comparator
    22. 22. NMØS Secret Ingredients •Use 74HCxx Logic as RF Devices - • 74HC86 to generate push-pull drive
    23. 23. NMØS Secret Ingredients •Use 74HCxx Logic as RF Devices - • 74HC86 as a Frequency Doubler •74HC86 can also be used as mixer •74ACxx - higher output, higher frequency
    24. 24. NMØS Secret Ingredients • Use OLD-SCHOOL, CLASSIC components! • LM3900 Quad Norton OpAmp • Low Power • LOW noise • Used on HW-8 • Excellent for Direct Conversion
    25. 25. NMØS Secret Ingredients • Use OLD-SCHOOL, CLASSIC components! • LM1496 Double Balanced Mixer • Better dynamic range than SA612/NE602 • Can operate from 12V • Can be gain-controlled • Also used on HW-8
    26. 26. NMØS Secret Ingredients CW Filtering – Response is Important! •Ringing causes listener fatigue •Gaussian response provides minimum ringing • Filter can be built using crystal ladder circuits, opamps or discrete transistor amps. • Gaussian audio filter can be attained by stagger-tuning stages. • Some filter design software programs do not get it right!
    27. 27. NMØS Secret Ingredients Gaussian Filter Response
    28. 28. NMØS Secret Ingredients Butterworth Response
    29. 29. NMØS Secret Ingredients Filter Pulse Responses
    30. 30. NMØS Secret Ingredients Stagger-Tuned Gaussian Audio Filter
    31. 31. NMØS Secret Ingredients Responses of each filter section
    32. 32. NMØS Cool Tools LTSpice IV - www.linear.com
    33. 33. NMØS Cool Tools Elsie - www.tonnesoftware.com
    34. 34. NMØS Cool Tools AADE - www.aade.com
    35. 35. Concepts from the NMØS Cookbook: •Be original ! •Question ‘prevailing wisdom’ •Borrow from the best •Aim for efficiency of • Power • Design • Ergonomics. •Take the extra effort to optimize performance •Don't be afraid of magic! HAVE FUN!
    36. 36. Bon appetit !