Building the Breadboard Radio “Splinter” – Part II

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Wow, I made a lot of progress tonight and managed to solder all the remaining components to the circuit board. I’d only planned to install the audio amplifier, but soldering went really quickly tonight. Again, the only issues I had with the amp section, involved dealing with the color-coded resistors. I simply can’t tell the browns, greens and reds apart. Fortunately, my wife can, hehe.

Once the amp bits were on-board I connected my earbuds and the battery and followed the testing procedure. I detected a rising hum in the audio while turning the AF gain and touching a specified resistor. Satisfied with the result, I dumped out the contents of the third bag of parts and got down to work attaching the components for the receiver and mixer.

I took a brief break to jump on the HF rig for a ragchew with some local guys, and returned to attach the transmitter components.

The silver square component in focus in the center is the 7.030 mhz crystal.

Now that’s a good-looking piece of kit. The silver square component in focus in the center is the 7.030 mhz crystal.

I ran into some trouble when I reconnected the rig to power and attempted the alignment procedure described in the build instructions. Essentially, I wasn’t hearing much of anything. The procedure called for me to press the “spot” button and zero-beat a tone while turning an adjustment screw. I wasn’t hearing that tone. Eventually, I did hear it, but the volume was incredibly low.

Fortunately, there was no issue: I’d neglected to spin the attenuator wheel fully counter-clockwise. This was specifically mentioned in the build instructions, but in my haste to power on the rig, I’d apparently ignored it. Once I set the attenuation properly, I was rewarded with a whistling carrier sound at an ear-piercing volume in my earbuds — so loud in fact, my wife, who was sitting across the room, told me it sounded like one of our grandparents were having hearing aid issues, hehe.

I attempted to zero beat the tone, then decided to check and see if any RF was getting out. I switched on the FT-847 and tuned it to 7.030 CW (The Splinter is rockbound to 7.030 mhz) and tapped the Splinter’s keyer only briefly, as I had not connected an antenna yet. I didn’t hear anything at 7.030, but I tuned down a bit to 7.028 and could clearly hear the Splinter’s tone.

And that marked the end of a long night. Tonight I plan on cannibalizing an RCA cable so I can connect the Splinter to my dipole to test the receive capabilities and perform more thorough calibration. I also need to buy some paint for the baseboard and build a Powerpole cable for easy connection to the 12VDC. Oh, and I have a crystal for 7.050 which I will install. While bound to a single frequency, the Splinter was designed with an extra set of sockets for dropping in crystals for other frequencies. A switch controls which crystal is active.

One thing that worries me is the relatively low volume of my sidetone when I’m in the transmit mode. I’m not sure if this is even an issue, as it may have been designed this way.

I do know that I want to build more kits. There is something very meditative and relaxing about soldering. If I could only see those resistor color codes…

Top view of the completed circuit board, waiting to be mounted on the wooden breadboard.

Top view of the completed circuit board, waiting to be mounted on the wooden breadboard.


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