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MKARS80 80 Meter SSB Transceiver – Part 3


MKARS80 80 Meter SSB Transceiver – Part 3

Construction of the MKARS80 Transceiver continues with the installation of the bag #4 components. This bag contained all of the active devices, as well as the crystals for the BFO and filter.

As these were just dropped into the holes, I didn’t take a lot of pictures during this phase. Here is the board after all of bag #4 has been populated:


Bag #5 contained the PIC chip, LCD display, controls and variable capacitor. I could not get the polyvaricon leads to fit into the holes on the board, and ended up trimming them thinner. At first I tried my side cutters, but they are getting a little dull. In the end, I used some toenail clippers! After trimming, the leads fit through the holes OK. 


Here is the component side with all of the bag #5 components installed (except the display and PIC chip).

 And here is the back of the board, with the controls poking through…
At this point, it was time to do the preliminary checks. The initial resistance check (12 volt input to ground) measured 1.9 K. Both 5 volt and 8 volt supplies were within a tenth of a volt of specifications. Next, I plugged in the pic chip and installed the LCD display. Application of 12 volts showed no smoke, and a faint hiss was heard in the speaker. Upon attaching an antenna, I heard and noise, and the normal interference I hear on 80 meters from the Plasma TV in the next room.

It’s important that the LCD does not stick up too high, so I installed a couple of the standoffs, and ran a straightedge across them and the LCD display. This way I could make sure that it didn’t stick up above the standoffs.


Pins were soldered into place, and everything was set. I turned the set back on, and two bars of blocks appeared where characters should be on the display. A simple tweak of R29 (contrast control) made normal characters appear.


It was a little out of band, so I adjusted C38 to bring it down some. In the end, I couldn’t get quite the whole 500 khz of range, but I’m thinking I would like to install the 10-turn pot/varicap modification anyway later. But I want to see how it works first.

It was still daytime, so no activity on 80 meters at this point. I’ll hook it up to a frequency counter to adjust the BFO tomorrow, and see how it sounds.

Migrated Comments:

2 Responses to “MKARS80 80 Meter SSB Transceiver – Part 3”

  1. Peter Says:

    Congratulations on a great build! I really enjoyed the kit too. Mine loses frequency lock after about ten minutes, presumably due to thermal issues. There are some modifications around that address this.

    Amused by your comments on lack of familiarity with the Metric system. Imagine how we feel about Imperial measures which make no sense to the rest of the world.



  2. Randy WB0SMX Says:

    Thanks, Peter. I visit your site regularly, as you have interesting projects, too.

    I understand the problem with the imperial system for the rest of the world. It really doesn’t have much logic behind it. I’m pretty sure I could get used to the metric system in about a hour or two, if we used it more than once every 6 months or so. They told me 40 years ago in school that we would be metric soon… I’m still waiting!


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