This is the build and test part of the project. I will record my progress as I make it.
I ordered the parts that I did not have from Mouser and the PCB from Aisler. The parts arrived first and a few days later, the PCBs arrived from the Netherlands via UPS. So, I went to work.
- I installed and soldered the parts for the 5 volt regulator, it worked the first time. With the double sided board and ground plane, it is much quieter than the prototype. The main issue with it seems to be that the output voltage is on the low side. I feed the Raspberry Pi with it and the Pi complains. After some looking around, I concluded that it is because the GPIO 40 pin connector was not fully pressed down. Pressing it down all the way solved the problem.
- Next I installed the parts and tested the keyer. I had made a mistake in the wiring of the reed relay. It has a built in diode and I had wired it backwards. Two cuts and two "white" (actually red, I did not have any 22 gauge wire) wires solved the problem. Stupid mistake on my part. Also, the 2.2K resistor is too large for driving the opto-isolater from 3 volt logic. I had discovered that the first time I built this circuit, but I made the same mistake again. In the short term, standup wired resistors did the job. In my second order batch, I got the SMT resistors and replaced the wired ones. I also found out that the ESD diodes that I was using were clipping the signals from the Raspberry Pi. These ESD diodes are unipolar (I had switched the model some time ago because of parts availability but had forgotten to make a note of it). I ended up using the magnifier function in the iPhone to see the polarity mark.
- After that, I installed the parts for the tutor and tested it. One of the cuts I had made to fix the reed relay mistake had disconnected the 12 volt feed to this section. One more wire and I was in business.
- Next I installed the parts for band switch reader circuit and tested it. I had to work on making sure that the 16 pin resistor network was properly soldered (it took a few trials) but no design or layout mistakes and it worked fine.
- Next, I had to pull out the Nooelec VFO board from the old project box and install it on the new PCB. That was not easy. I eventually resorted to using the Dremel cutting wheel, but it worked.
- Finally, I installed the serial interface connector.
Everything is now tested and working.
Here is a picture of a fully working board short of a few parts that I have on order. The two large capacitors are the input and output capacitors of the simple switcher. The heatsink next to the larger capacitor on the left is the simple switcher chip itself (TO-220-7 package). The square black inductor to the left of the smaller capacitor is power supply inductor. Below it is the Schottky diode. The blue printed wiring board mounted in the middle is the DDS. The other two heat sinked devices on the lower right of the board are the output transistor and the matching temperature compensating transistor. The board is fully connectorizedz to make it easier to install and maintain.
My next step is to install the components in the enclosure.
The back panel is quite busy, so I spent time working on its design. Below is the drawing.
Then I went into the shop and cut metal with a combination of drill, Dremel, and a collection of files. The large holes for the fans are made using a 3" bimetallic hole saw. Using it with a battery powered hand drill was a challenge even with using a lubricant (I used water). Earlier, I had practiced on a sheet of scrap steel and that was even harder, so I resorted to an electric drill that did the job but overheated. Next project, I will use the drill press in the radio club shop.
...and here is the finished product.
As I was testing the new package with the radio, I noticed that the band switch did not work. The band switch shorts the band select line to a common pin (pin 4). I had assumed it was grounded. It is not. So, that is a second white wire.
There is ample room left on the left side of the enclosure for a digital filter (otherwise, it's hard to hold a CW QSO with a modern radio on the other side). I think I am also going to replace the SoundBlaster dongle with a built in sound card that also has PTT control (fiddling with the VOX as I change bands is no fun). Also, I have found the fans annoying, so I will replace the fan power interface and include a temperature sensor in it turning on fans only when necessary.
This is how the station looks with the new package for the auxiliary components:
And here is the updated schematic.
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