6 Feb. 2020 – Construction Contest winners’ talks

First up was Rob, M0IXM. This was his first entry into our contest with his Capacitive Touch CW key. The original design was published by M0UKD on his website.  The board is rather small and uses surface mount components. The board details were published on the website and Rob sent the Gerber files to China (where else!) and had several boards made. Using a hot air paint stripper, Rob was able to solder the parts on to the board, however, he found that too much air blew the parts off the board and resulted in starting over. He also found that trying to find the pin one on the ICs needed more power than his magnifying glass could provide, so he resorted to a stereo microscope, which worked fine. Rob was able to demonstrate the key’s use when connected to Alan’s QCX CW transceiver,

The winner of our Kit Class was Alan, G4PSO who built the QCX 5W CW transceiver. This is a one band unit and Alan chose to use 20M. Alan explained he bought the kit two years ago but didn’t make a start in building it, mainly because he spent a good while last year visiting New Zealand. He started by downloading the instructions from the internet, all 141 pages of it!  Rather than printing it out, he opted to read it on his tablet.  He did show a digital video version to members to show how much detail there is on offer to the builder. Alan explained the finished board can be used as a volt meter to measure various points on the board to confirm proper operation. The board also contains a Signal Generator, a CW reader and a method of measuring power out. Lot’s on offer from such a small board.

Don, G4LOO won the Weekend Special with a project that seemed more than a week end’s work. It was a Test Jig to enable testing the pin in and out of the Racal amp control boards he wanted to make use of in his 23cm 500W linear amplifier.  He had several surplus boards and wanted to test to find one that actually worked.  The end product ended up in Don’s Major Project winner. This project started life as an ex TV YD1336 cavity, modified as per Dubus article by G4DZU.  It was said to tune 70/23cm. Included was a valve with a slightly bent anode cooler, which proved to be unusable due to cracks in the ceramic base. The cavity was supplied without fan, chassis or circuits. Don provided the main case and everything needed to support the cavity. The finished project required a fan capable of producing much more air flow than usual,  2.5 cubic meters per second, to be exact!  The required control, monitoring and reporting is carried out using Arduino boards and the results are displayed on the separate control box.

A view insid Don’s amp
The control circuitry