The following picture shows test signals from the part assembled PCBs being observed and measured on my kitchen table in late January 2011.
The PICs were programmed using my Picket3 clone and the keypad used in the tests was taken from a scrapped telephone and the LCD module was bought new on Ebay from a supplier in Hong Kong.
Once it was established that this lashup functioned ok it was time to think about a suitable enclosure and how best to package up all the parts.
It was my intention to eventually use this DDS as a VFO for a multiband BITX project based on either the 2E0ZHN smd or a G6LBQ version both of which I have already built and tested earlier using a N3ZI DDS but which lacked an output to automatically switch BPFs or LPFs.
As I previously had some experience in using the Aluminium cases supplied by Maplin I decided that their box type AB13 order code LF14Q measuring 6 x 4 x 2 inches would be suitable, so on that basis before I did any serious metal bashing I made up a mockup of what I had in mind to get an idea of part placements using PCB spacers and Blutack to assist in locating and affixing all of them.
The photos above show the mockups. Note in order to squeeze the PCBs into the standard Maplin case, about 1/8 inch of the flanges needed to be removed from the top of the end sides of the lower half of the case, but otherwise it is a perfect candidate for the job.
The mockup D Sub Connector housing shown attached to the rear of the box is how and through which all the output and input control lines for the BPFs and LPFs will be routed. I realised early on that although this DDS provides positive 5 volt signals for this purpose they are limited by the PICs to 25 mA maximum and therefore in order to drive relays for LPFs etc some level changing would need to be employed eventually. This I reckoned could be best done externally and most neatly utilising a ULN2803 Darlington Driver Array as an add on module built into a D sub connector housing to suit individual interface circumstances as they arose.
The next job was to mark out and hand drill and file all the holes and apertures required for mounting the parts. All this work was done using hand tools on the kitchen table during late February and early March 2011.
The aluminium box was washed and cleaned ready for a trial fit of all chassis and panel parts and sub assemblies. Miniature LEDS used to display the Band selected were mounted on a piece of perf board and connected to the D Sub 25 way connector which in turn connects to the main DDS PCBs using Molex connectors.
The main PCBs were then stacked using metal and nylon spacers ready for connecting to the subassemblies and final installation inside the case.
The photos below show the DDS finally assembled, powered up and working.
DDS tuned to 28.000000 MHz
Scope display of output of DDS tuned to 28.000000 MHz
Scope display of output of DDS tuned to 7.000000 MHz
DDS tuned to 7.000000 MHz showing the LED for the 40 Meter Band illuminated
DDS tuned to 14.000000 MHz showing the LED for the 20 Meter Band illuminated
My next job is to use this DDS as a signal generator to align and test a prototype G6LBQ Multiband BITX BPF PCB which I recently received this month from Sunil and which I have since populated and assembled and am now ready to test.
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