The Loudspeaker part 4

This is the classic electrostatic loud speaker. the design is imperfect, but is revisited even today by audiophiles looking for more accuracy. Nakamichi just unveiled a version that costs about $9,000 per pair. A healthy descendant of patent No. 1,983,377.

One of the big down sides is that they use very high voltages to operate. The 5000 volt DC bias is usually supplied by a power supply running off 120 volt AC electrical circuits which is dangerous enough I'd not recommend it be anywhere children can reach. This nut makes them.

They use a thin flat conductive diaphragm. It's usually a plastic sheet impregnated graphite. This diaphragm is sandwiched between two electrically conductive grids, with a small air gap between the diaphragm and grids. For low distortion operation, the diaphragm must operate with a constant charge on its surface, rather than with a constant voltage. hence the need for the juice and the tube amp and the transformer and the dedicated circuit in the basement. [OK, I'm exaggerating but you're starting to get the idea what nobody uses these.]

The reason they exist is that they are amazingly precise. Which is why the audio nerds at Stereophile Magazine get all dreamy-eyed when some manufacturer ships them a pair for testing. The diaphragm described above is driven by two grids. Using grids on both sides cancels out non-linearity. The result is almost the total elimination of harmonic distortion. it sounds crisp to say the least. The downside to this design other than voltage and cost is that unlike your cheapo speakers it projects this perfect sound over a very narrow area. It's sonic field is very narrow, especially for those of us that are getting spoiled by surround sound these days.

In 1957 Quad ESL marketed as the first real electrostatic loudspeaker, referred to as the Quad 55 or the Quad 57. Those bad boys were designed by Peter Walker (pictured) and David Williamson. But they were based on a patent owned by Edward W. Kellogg's from 1934. that patent was based on a research paper he did way before that in 1925 while still working at General Electric. Kellog worked in tandem with a gentleman named Chester Rice. They published a paper on amplifier design that was important in boosting the power transmitted to loudspeakers. In 1926, RCA used this design in the Radiola line of a.c. powered radios.

K, W & the mighty Missisippi

In the 1800s broadcasters adopted call signs to aid in signaling. This practice continued when ships began to use radio. [popularized by the sinking of the titanic] Initially brodcasters determined their own calls. This led to duplication and confusion.

In 1884 the first effort to standardize this occurred. The head of the Federal Bureau of Navigation, (FBN) Eugene T. Chamberlain, exorcised a new vaguely worded statute and assigned marine-radio call letters. His previous career as Ships on the Atlantic and gulf coasts were assigned calls beginning with K, and those on the Pacific coast and Great Lakes were assigned calls beginning with W. It is unknown why he chose K and W.

In 1906 Berlin International Wireless Telegraph Convention (BIWTC) declared that all ship and shore stations should have unique call signs consisting of three letters. The U.S. did not ratify the BIWT convention until 1912. (why are we always behind Europe?) That year Congress empowered the FBN to license land stations in addition to the marine stations. Official documents issued in 1913 confirmed the practice of assigning W calls to stations in the west and K calls to stations in the east.

The following year Congressimproved the system slightly deciding that the Pacific coast would get W for ships and K for land stations, the Atlantic and gulf coasts would get K for ships and W for land stations. This made it more simple to distinguish a marine broadcast from a land broadcast.

It was not until 1923 that the missisippi became the dividing line. Prior to that Texas as a gulf coast state had W's! The dividing line started at El Paso and worked its way east the then north.
see map: http://earlyradiohistory.us/kwbigmap.gif

There are many exceptions to the K&W rules even today. Below are some contemporary examples. These are all considered "heritage" call letters and they are highly valued.
KYW-AM 1060 Philadelphia, PA ...the K furthest to the east
WIL-AM 1430 St. Louis, MO
WOAI-AM 1200 San Antonio, TX ...the furthest W to the west.
WOI 90.1 Des Moines, IA

Exceptions along the border are commonplace as the calls are assigned by city of license and not the location of the transmitter. Minneapolis , Memphis, New Orleans and other markets straddle the line and each contain multiple exceptions. A simple explaination here:
http://www.dxing.com/callsign.htm

For all of his trouble-making, eventually the Navy named a ship after Mr. Chamberlain. It is a Liberty Model.