Shed workshop #5: Power supplies

At the last “formal” workshop for the year on 9 September 2018, held at ZL2XJ’s QTH,  we were given tips on the construction of power supplies by three members (Don ZL2BL, Bernard ZL2BD, and George ZL2AG).  This included:

  •  a foolproof (but weighty) bench power supply for valve circuits (short circuits no problem) using readily available transformers and valves (Don ZL2BL)
  • two different kits for variable voltage bench power supplies, acquisition of low cost 13.8v switched mode power supplies, and tips on how to quieten down RF noise from these power supplies (Bernard ZL2BD)
  • low cost 13.8v transformer-based power supplies built into older desktop computer cases (George ZL2AG).

Over the summer we will have informal workshops, where you are welcome to “bring along the soldering iron” to work on projects, whether that be a uBITx transceiver, a magnetic loop antenna, or a power supply or whathaveyou.

Relevant documents

Who had the competitive edge? The August meeting

At the August 2019 meeting we set out to find out which team had the competitive edge in finding a set of crystals that would be useful in a 12 MHz crystal filter?   Bernard and Frank found 3 crystals within 30Hz of each other.   They were part way to getting a set of eight.   A bit harder than everybody thought, but many learnt some techniques in sorting out crystal suitability.    The other two teams each found 2 pairs of crystals that would meet the required specifications.

Follow on Magnetic Loops Shed Workshop #4

Bernard ZL2BD hosted another shed workshop on Sunday 5 August 2018 from 1pm -3pm at his QTH.  Due to interest in  Small Magnetic Loop antennas, this month’s workshop was a follow on session to assist those committed to construct a loop antenna. Several people purchased Capacitor Kits to make an air spaced butterfly capacitor.  Progress is being made on sourcing LDF4-50 1/2” coax and possibly LDF 5-50 1” coax for the loop material to be made  available to those who want this material.  It’s not too late to order a kit if you haven’t done so. 

Bernard talked about practical matters, such as how to construct the capacitor enclosure and plastic waterpipe housing for the antenna, as well as practical details on putting together the capacitor kit, and selection of motor drivers and gearbox, etc.

Mike ZL1AXG talked to a design that provides for real-time tracking and tuning of a magnetic loop.  A circuit board is available to purchase from North America.    He talked about where to source  components including the processor (Teensy 3.2), a 100 step rotation encoder, 51uH twin coil chokes, the stepper motor driver chips,  and the stepper motor and gearbox.

Bernard provided pre-calculated details for a 2m diameter 40m loop, which most seemed keen to build.