KK7BCO

On our second podcast gathering we launched our first group build project. We are building a signal generator, a sine-wave oscillator that should cover the HF ham bands.

We are using the Soldersmoke Podcast Discord server for the group builds, mostly because there are a lot of people on there who are a lot better at this stuff than we are. You can join that discord HERE, and then go down to the bottom of the channels to find Beginner Project Series. The original article that the project is following was written by George Dobbs G3RJV (SK), and can be downloaded HERE.

Charlie NJ7V found the inductors used by Dobbs are hard to get now, and the approach of winding on a toroid sounded a little daunting to me, with 80+ winds in a donut. So I suggested that I was going to pull a ferrite rod from an AM receiver, and try winding them on a stick, which sounded much easier. I took some measurements of the existing 3 coils on the ferrite rod (120x10mm), then out of curiosity asked Copilot how to make the windings of the values I needed. It did its thing and gave me some numbers that didn’t work, but I gave it new measurements and a second attempt got me close, and I was able to get the needed values by trial and error.

I also removed the variable capacitor from the receiver, which had several gangs. This page shows my notes on the bits I harvested.

And this is how I started.

I then proceeded to populate the board. First thing I stuck on was an LED to show power, I gave it a 220R series resistor, following what I did on the Soldersmoke DCR build (also in the Discord). I soldered the ground legs of the capacitor to the board, then added a power rail, which was arguably unnecessary as the circuit is pretty small.

I draw on the schematic to remember the pinout of the “three legged dudes”, then arrange them and check my process several times before soldering. Laying out most of the schematic using the Manhattan Style is very intuitive for my dyslexic brain. No need to try and follow strips like Veroboard. No real planning as such, I just try to make things tidy and ideally look nice.

I also decided to use a 6 position switch, taken from a bone bin at the Hamfest the other day, the face plate from a Heathkit EK-1. 6 positions means that I was able to wire in the original windings on the core also, mostly for curiosity at this stage.

I was able to roughly cover 900kHz to 30MHz, and from my initial knob turning it looks like I can get most of the HF bands on one winding, since the capacitor has a wider range covering 10-270pF. The signal seems to be pretty stable, which is surprising since I built it, and it is not even in a box.

Now I need to figure out how I want to package it. How to make it useful. And also how to count its frequency. I’d picked up the frequency counter thinking to gut it, but it is hard to gut a working Heathkit which is probably much more useful as itself. So yeah, I may end up buying one of the $20 frequency counter displays in Juliano Blue. Currently I have spent under $5 on parts, including the frequency counter. Everything else came from my bins and some scrap boards.

More to come.

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Filed under: blog,DIY,Uncategorized - @ March 17, 2026 2:30 am