Category: Events

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7 November Shed Meeting

Our monthly shed meeting was held at Mike ZL1AXG’s QTH in Churton Park on Sunday 7 November. Two topics were covered:

  1. Receive magnetic loops
  2. Part 3 of the Simple SSB Transceiver series: Band pass and Low pass filters (Mike ZL1AXG)

Bernard ZL2BD gave an update on experiments with receive only magnetic loop antennas including the differences between tuned and untuned loops (See the attached paper) and Mike ZL1AXG talked about his recently acquired MLA30+ Rx loop that can be used in conjunction with the portable Tecsun PL-330 receiver.

Mike ZL1AXG also gave his third talk on the Simple SSB TXCVR. The talk covered construction and testing of band pass filters and low pass filters (See attached powerpoint presentation for more details).

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ZL2BD HF Active RX Loop Project 2021

1 file(s) 1.63 MB
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ZL2BD HF Active RX Loop Project 2021

1 file(s) 1.43 MB
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ZL1AXG - Part 3 of Simple SSB Txcvr - LPF and BPF

1 file(s) 3.47 MB
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Shed Workshop 1 August 2021: Four approaches to knowing whether a band is open

How do you know whether a band is open?

There are a number of different ways to know if there is propagation on an HF band. Listening for stations on a band is not necessarily the best way to determine whether there is a band opening. If everybody is listening, and nobody is calling then the band will still seem to be dead. 

John ZL2XJ and Mike ZL1AXG demonstrated the use of beacons, DX clusters, the reverse beacon network, WSPR that can all help in determining the likelihood of a band being open.

The QTH for the Shed Workshop held on 1 August 2021 was that of John ZL2XJ at 9 Ridley Green, Churton Park.

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Presentation on four methods to determine whether a band is open

1 file(s) 713.38 KB
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Quick guide to Beacons and DX clusters with links

1 file(s) 25.32 KB
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Quick guide to Reverse Beacon and WSPR websites

1 file(s) 15.16 KB
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Shed Workshop 4 July – High Current Switch Mode PS and Mixers in the Simple TXCVR

Our July shed workshop was held on 4 July 2021 from 1pm to 3pm at the QTH of Mike ZL1AXG (2 Derry Hill, Churton Park, Wellington).

Mike ZL1AXG is building Charlie Morris ZL2CTM’s Simple SSB Transceiver.  This is a modular design and as each module is completed it is tested.   In this second session Mike discussed design and construction features and demonstrated the testing of completed modules.  The module in the picture is one of two double balanced mixers constructed from scratch on veroboard (Photo from Charlie ZL2CTM)

Bernard ZL2BD also presented on high current Switched Mode Power Supplies suitable for driving Kilowatt amplifiers.  He designed a system using two SMPS at 24 v to power a 2Kw linear for another amateur.  The SMPS turned out to be very quiet electrically and they are available in 12v and 13.8v and other voltages as well ex China at very reasonable prices. 

Tea and coffee were available following the workshop.

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Shed Workshop 13 June: An antenna ecosystem and Constructing a simple SSB Transceiver

Controlling field equipment under an ecosystem approach

The June Shed Workshop was held a week later than usual – from 1pm to 3pm on Sunday 13 June 2021 at Mike ZL1AXG’s QTH due to Queen’s Birthday weekend getting in the way.

Mike ZL1AXG and Bernard ZL2BD gave an introduction to the concept of an antenna ecosystem, in which a range of antennas could be controlled by a single microprocessor control system.  This includes remote antenna switches (with just one antenna cable into the shack), 4 square switching, directional switching of beverage antennas or similar, tuning of magnetic loop antennas, and rotator control for beam antennas.

Mike ZL1AXG also introduced Charlie Morris’ Simple Transceiver for 80m SSB. He showed off some of the modules that are under construction, and outlined in a block diagram the design of the transceiver. He demonstrated how the audio modules could be tested using a multi-meter, signal generator and oscilloscope by inputing a signal from the signal generator at 1KHz in the front end of an amplifier and measuring the voltage on the oscilloscope or multimeter at the output end.