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Re: spark gap noise suppression

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Tesla list wrote:

Original poster: <davep@xxxxxxxx>

> Has anyone ever tried to make things a little quieter when running your
> coil?
This was standard problem/issue in early wireless stations.

> I was looking at the muffler on my central vacuum unit and it has a
> muffler that quiets the unit by about 50%. Borrowing from that idea, I
> was thinking about building a box lined with some type of foam with
> openings on each end.
Commonly, in the old days, the gap was enlosed for sound
suppression, especially when high poweres were used.
Sometimes 'in its own room'.

A point to Ponder is that many sorts of foam are Highly
Flammable. (cf the Station Night Club fire.) I'd be
real careful, in picking. Perhaps 'fiberglass insulation'?


It was indeed common to have the spark gap in an entirely separate room - long leads didn't matter much at the low frequencies in common use. On the really high power stations the noise was really deafening and such precautions were a necessity and not just a convenience. There is one type of very silent gap worth considering - the quenched gap. Completely enclosed and almost silent. I have a WW1 surplus gap which works fine on my 3" coil run from a 12 kV, 60 mA transformer. Sound can't be detected with streamers present and even when they're shorted the thing is barely audible. Several people here have reported making quenched gaps with varying degrees of success. Straightforward machining job but not trivial.

As for sound insulation, my alternate cylinder gap is enclosed in a small wooden box with a couple of layers of fiberglass insulation. Not silent but much better than with it running in the open air. Of course, the crash of the spark is part of the fun!