Resonant Speaker for CW

You're saying to yourself: "What in the world is that?!?" It's not a spitoon for people with good aim, It's not a potato gun, or even one of those water-rocket launchers. It's plain and simply the one project that I've built that has impressed me the most. If you think that CW stands for Copenhagen Widget, read on...
After days on end of playng with active filters for CW and having little success I stumbled on this idea to make a speaker that resonates at 800 Hertz. (Yet another addition to the long list of things I wished I'd thought of myself!) Thanks to WE6W I didn't have to. And thanks to N5ESE for all the research on perfecting it as well as the detailed drawings. N5ESE recommends using a 4" diameter sphere for the main enclosure. He used a plastic Christmas ornament builders ball which he found at a hobby/craft store. I happened to have an old Copenhagen spitoon which fit the bill.
The speaker I used was a tweeter pilfered off an old boom box. It was a 4W speaker and my rig needed 8-16W so I seriesed some resistors to make my amplifier happy. I cut the spitoon mouth to accept the 2" PVC and the fact that the mouth is removable makes it easy to service. I used a wooden dowel for the plunger and wrapped it with teflon tape in two places for the seal. I also put a rubber rig foot on the end of the dowel to keep it from disappearing up the tuning tube.
I ran a sweep of the audio frequencies and there is a large peak at exactly 800 HZ and very little at the overtones. The slidable insert down the throat accomplishes that with a little trial and effort. This little baby cuts most of all the QRM and QRN. Thanks again Ed and Monty, (I'm still working on that non-existant list of things KD7REM has thought up.)
Back to QRP Stuff

Home to Rock Radio