The Freedom7 HF Transceiver Saga
Problem – Starting the Climb
This maker has decided to prepare a comprehensive posting each month, to journal the progress of my Freedom7 Transceiver at the bench. I am also doing one called, “News from the Shack” as well.
The goal is simple, but not easy: build something real, understand it deeply, and share the lessons along the way — including the mistakes. This month’s focus has been the receive-chain, specifically a low-noise amplifier (LNA) and revisiting my band-pass filters.
Nothing about this process has been straightforward. Designs change. Assumptions fail. And every step forward seems to reveal two more things that need attention.
Early Success — Momentum Builds
This month I completed the design, assembled the components, and tested a low-noise amplifier at the bench. I think the design changed about three times, and while I support fast failures, I now have a working LNA.
I also returned to the band-pass filter(s) and redesigned them on paper as Butterworth modeled 3-pole, series-coupled textbook filters. My choice of components leaned toward larger air-core inductors with high-Q values. The capacitors were carefully selected as well, and two had to grow beyond the 0805 packaging because I couldn’t get the values I needed due to dielectric material limitations. I forget the exact package, but it was basically the next size up physically. I’ll achieve my maker title soon I’m sure.
On paper — and even in simulation — things were starting to look good.
Setback — When Reality Pushes Back
Lessons learned always come from mistakes, and I plan to document the detailed LNA design in another posting. I’ll say here that the design leaned heavily on reference material: books, PDFs, posts, AI, and anything online I could get my hands on.
The overall design was modeled using LTSpice over several iterations. Change something, simulate again, refactor, repeat. LTSpice is a great tool for initial design, and eventually I had results that looked promising.
That’s when I made the classic assumption:
“I’m ready for the breadboard.”
Wrong.
Crisis — Under the Big Top
My attempt at a breadboard solution was an utter joke.
When I connected my scope, I wasn’t looking at a clean RF design — I was under the big top at the circus that just came to town. Noise everywhere, instability, and behavior that simulation never warned me about.
That moment forced a realization:
This design would have to be tested in its final form — on an actual PCB, possibly with an RFI shield — not floating on a breadboard, with parasitic capacitance, and with an array of jumper wires (little antennas) like some classroom experiment.
It was a humbling checkpoint. And, now I know, “don’t do that!”
Recovery — Iteration Becomes the Way Forward
The band-pass filters went through multiple iterations, both on paper and PCB. The LNA followed the same path. One clear solution moving forward is to embrace the iterative mantra:
Design. Build. Test. Refactor. Repeat.
Simulation gets you started. Reality teaches the lesson.
My next component will be a very stable and accurate variable frequency oscillator (VFO), or local oscillator, slated for March. I have the start of a schematic and have identified an extremely stable and low-noise square-wave solution using a more expensive chip than the common Si5351a many hobbyists use.
This part of the climb feels different — less guessing, more informed decisions.
Better Place — Higher on the Mountain
Each month’s progress brings me closer to something bigger than just a radio. This journey is about understanding, building, and hopefully inspiring others to step away from black boxes and toward real RF knowledge.
Stay tuned and come back, y’all.
Please check back periodically and watch my progress here. I welcome WordPress subscribers. I’m doing this for myself, yes — but also to spark interest and hopefully influence younger generations to become Makers too.
My About page provides the background of the Freedom7 HF Transceiver project.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com.
And if you believe understanding our radios matters more than sealed boxes, you can subscribe here:
https://kr4bad.com/?subscribe=1
73
KR4BAD
David
Why This Article Uses the “No Easy Way” Story Model
This post follows the No Easy Way structure from Steve Rawling’s Pipdeck Storyteller Tactics:
- Problem — Beginning a complex RF journey with no shortcuts
- Early Success — Working designs and encouraging simulations
- Setback — Breadboard assumptions fail
- Crisis — The “circus” moment on the oscilloscope
- Recovery — Iterative engineering becomes the method
- Better Place — Greater understanding and forward momentum
The climb isn’t finished — but each iteration moves higher up the mountain.
Leave a Reply