JB wrote:



enough to avoid problems with the transmitter. Multiple series gaps only
raises the firing voltage, but the breakdown voltage will be set by the
largest gap in the series. A gap at .035 will fire at about 2-10kv
depending on humidity. You only want it wide enough so that it won't arc

Humidity doesn't change the breakdown voltage very much. In fact,
increasing humidity increases the breakdown voltage. One correction
table for a "rod gap" with 1/2" square electrodes has a 10% correction
going from 15 torr to 30 torr water vapor pressure and a -16%
correction going from 15 to 2.5 torr, which is nowhere near the 5:1
variation cited above. Interestingly, on this basis water vapor is a
better insulator than nitrogen, since density of the humid air is
actually less. Typical breakdown voltage tolerance on a rod gap is +/- 8%.