| 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.) |
 |
