I was wondering if making a low frequency RF circuit on a breadboard is viable.
In my experience, yes, but you may need to take a few things into account.
- Some breadboards are better than others. The maximum frequency I've seen operating cleanly and reliably on a breadboard is 2 MHz. I've also seen breadboards that couldn't handle 200 kHz.
- You need to consider the maximum frequency present on the breadboard, not the largest "fundamental" frequency. For instance, a square wave signal (such as a clock or the 555's output) have very large harmonics up to maybe 5 or 7 times their fundamental frequency. If the breadboard can't handle these, then the clock will become distorted (low-pass filtered); additionally, if those harmonics spread through the breadboard, they'll distort potentially all your signals.
- Bypass capacitors become important as the frequency increases. Put one cap everwhere a circuit connects to the supply or ground, and you may have to sprinkle them around wherever high-frequency harmonics appear.
If you are insanely attentive to layout, yes. That means:
- Bypass everything with as short of wires as you can,
- Lay your wires down flat on the board (which pretty much means you'll be doing a lot of bending and possibly custom-cutting of wires). Big loops will kill you for sure.
- Be willing to use twisted-pair, or even small coax to go from one "major" stage to the next (i.e., if you're putting multiple breadboards together, use transmission line).
- Position your components so that the sensitive connections are short.
- And, of course, everything that I left out.
Yes, it's POSSIBLE but is never going to be as stable as a PCB. Best you can do is avoid wires crossing, keep them as short as possible, and ensure your connections are good.
Actually, in the early days of radio when RF was below 500,000 CPS *** , most gear was built on a wooden breadboard with no concern for stray coupling. And it worked (sometimes). Good luck with your Branley coherer and watch out for the wouff hong.
*** CPS is a unit of frequency named for Charles Proteus Steinmetz.