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Making Waves – Building the KANGA Products OXO Transmitter Kit (Part 2)

December 21, 2019 Leave a comment

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Following on from yesterday when I started building this excellent kit from Kanga Products, I have today managed to build the rest of it, all that it needs now is a power source and a Low Pass Filter before it can be plugged into an antenna.  Neither of these are included of course but the power supply can be a simple 9V battery (or 12V PSU) and the LPF a simple 5 or 7 pole LC filter.

7The completed board

Overall the PCB was easily populated with the components and personally I shall add a polyvaricon to the terminal beside the XTAL labelled Cvar.  The option was to either bridge this and have the frequency rock set to the XTAL value or add a variable capacitor to enable a swing on the frequency.  Therefore I am going for the latter option.  If I have any criticism of the kit it is that the XTAL(s) supplied are in a large can – I would probably replace them with the smaller low profile ones – and they are supplied at 14.050 and 7.028MHz, not the QRP frequencies of 7.030 and 14.060MHz.  I am planning on designing/building a switched XTAL bank to allow operation on all the QRP frequencies from 80m – 20m (possibly 15m) using XTALs I have here.

 

I have yet to do a smoke test and check the stability of the RF generated yet but this will be in the next stage as I have other things to be doing now.  I shall be checking both with and without a LPF straight into a dummy load before I plug it into an antenna of any sort though.  I also need to find a suitable enclosure for it.

Making Waves – Building the KANGA Products OXO Transmitter Kit (Part 1)

December 20, 2019 Leave a comment

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As it’s nearing Christmas 2019, I decided to treat myself to an OXO TX kit from Kanga Products UK.  This is an updated version of the OXO transceiver made famous by the late GM3OXX now providing a multi-band version.  So I ordered it from KANGA and it turned up here yesterday in a jiffy bag/envelope.  Taking it out it was nicely packaged in a sealed plastic sleeve.

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Making sure I had all necessary test equipment ready (including the Sandford Wattmeter also from Kanga Products) I set to work to start assembling it on the CVO towers workbench.

Opening up the outer sleeve and removing the contents I was pleased to see that all the components were sorted in separate bags of resistors, capacitors, transistors, etc.  tis makes individual components much easier to find as opposed to just having everything dumped into a single bag.

3 everything sorted into individual bags

The instructions needed to be downloaded from the website and consisted of a three page .PDF file.  To quote one paragraph from them:

“Though the fitting of the parts is straight forward, it is highly recommended that all components are soldered in the order they are listed in the component list”

Although this may seem a no brainer it is good advice as you can then mark off each component as it is fitted and it runs in order of resistors, capacitors, transistors, crystals and then connectors.  This also follows the order of the bags.  My only criticism here is that the coil isn’t mentioned in the list but is mentioned in a separate paragraph.  It needs winding by hand and is 17 turns of 24SWG ECW wound on a very small ferrite toroidal core.  This is surface mount and laid flat on the PCB and should be mounted first ideally.

4The PCB is nicely printed and fairly easy to follow

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So, contrary to my earlier advice I first fitted the resistors to the board.  Fairly easy through hole devices and Dennis, from Kanga UK, has kindly listed the colour coding of each resistor beside its value in the list.  Not really necessary for those of us in the know but for those not familiar with resistor colour codes a handy help.

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Next I wound the coil.  The former is very small and this can be fiddly.  Note, if you are going to build one yourself do leave the ends long as if you cut them too short….  Anyway once wound I fitted the coil to the board using the plastic screw, washer and nut supplied before soldering the tails to the pads on the board.  Contrary to popular belief the enamel coating on the copper wire doesn’t melt away to reveal bare copper when you apply a soldering iron.  I use a Dremel Multi-tool to remove some of the enamel coating before applying solder.  Once this was secure I then applied the capacitors in order, with the large electrolytic one being fitted last of all, ensuring the polarity was correct.  that was it for today as work got in the way but I will continue when I next get round and will hopefully have it complete and ready to test next time.