February 5, 2012

KN-Q7A Single Band SSB Transceiver Kit - Step 2: Audio Amplifier

This is the 5th article in our series on building the KN-Q7A Single Band 40m SSB Transceiver Kit. In our prior article, we fabricated an Anderson Powerpole to 2.1mm Connector Pigtail to supply power to our kit through the jack. In this article we proceed with building step 2: audio amplifier.

We followed the step-by-step instructions for installing each component.  However, when we got to the capacitors and resistors, the instructions simply said, "solder the remaining capacitors and resistors; when finished, it will look like the photo".  Each component is marked on the circuit board which helped.  Using the circuit board and photo, we were able to figure out which parts to solder and the location.  We would have preferred a little more guidance.  In our opinion, it would have been helpful to provide a checklist identifying each part to be installed.  We did like having the picture as a guide though a larger photo would be helpful.
KN-Q7A circuit with the power supply and audio amplifier sections installed
The final activity for completing the audio amplifier is to test to confirm it is functioning.  We really like this approach since it gives the builder confidence that the build is progressing as it should.  It will also make it easier to identify and correct problems should they emerge during construction.

Testing the audio amplifier involves plugging a speaker into the speaker jack and confirming noise is heard from a speaker.  We rummaged through our junk box and found a small speaker previously salvaged from a laptop computer.  We also found a suitable cable with a miniture phono jack already soldered onto one end.  We quickly stripped the cable and soldered it to the miniature speaker as a testing aid.
Speaker soldered to speaker jack as a testing aid
We plugged the speaker into the jack and followed the test instructions to produce a clear noise from the speaker.  This confirmed that our audio amplifier was working.  Perfecto!

Lessons Learned
  • We would prefer to see the instructions list out the specific parts to be installed rather than trying figure it out from a photo only.
  • Powering up with the aid of 2.11 pigtail we made previously was a big help.
  • Building a simple speaker plug soldered to a speaker with junk box parts made testing quick and easy.
  • We really like the function test at the end of each step.
In the next installment we will proceed with building Step 3: Detector / Double Sided Band Modulator.

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