re: gap losses

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>


Normally, one selects spark gap electrode material which is long
lasting such as tungsten.  Such metals may also assist in
quenching compared with metals such as zinc or magnesium.
According to "principles of radio communications" by Morecroft,
metals such as zinc or magnesium give a lower gap resistance
than silver or copper.  I assume this is because of the greater
number of ions tossed into the arc using zinc or magnesium.
It may be possible to lower the gap resistance by using such
metals, if the arc can still be quenched adequately, and if the
higher rate of electrode erosion can be tolerated.  

Morecroft goes on to say that the effective gap resistance in 
spark gap radio circuits is usually less than 1 ohm, and is
usually only a few hundreths of  1 ohm, based on studies of
arc heating effects.  He also reports that the arc resistance
gets somewhat lower as the frequency is increased. 

If I remember correctly, work by Bert H, and Malcolm showed
the gap losses to be about 15% in a well designed TC.  
I measured something similar in some crude tests I did.

Cheers,
John