Final Shed Workshop for 2021: Portable MagLoop Tuner
Our final shed workshop session for the year was held on Sunday 5 December from 1pm - 3pm at John ZL2JPM's QTH at 9 Ramphal Terrace in Khandallah.
John ZL2JPM talked in more detail about his portable microprocessor controlled QRP mag loop antenna that he briefly introduced to us at the October meeting. John won the annual Blackwood Cup for 2021 based on this entry.
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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 [wpdm_package id='3540'] [wpdm_package id='3549'] [wpdm_package id='3544'] [wpdm_package id='3546']
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…
Shed workshop #3: Magnetic loop antennas
Bernard led off on the third shed workshop for 2018 which was on the topic of "Magnetic loop antennas". These antennas are great for getting better signal to noise levels out of typical noisy suburban environments. They are also compact and can be mounted on a boundary fence or building to blend into an urban environment. On transmit they are less sensitive to changes in the surrounding environment (e.g. resonance changes observable on wire antennas with wet weather). Ten members turned out on Sunday 1 July 2018. A summary of his presentation, theory of magnetic loop antennas and instructions for constructing these antennas can be downloaded here: [wpdm_package id='3462'] Bernard can be seen giving a presentation to kick off: Several examples of loop antennas were available for inspection including this multiband loop for 15m through 10m: And a close up of the butterfly tuning capacitor: The feedpoint and feed system: And finally, a mag loop controller box that Bernard has constructed (he has several!): A special price has been worked out for branch members who wish to assemble their own butterfly-style tuning capacitor. This is required if you wish to make a small magnetic loop for receive and transmit.