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Camera Shutter Noise: At first the "open flash" method was used: with the Camera shutter noise on a tripod, the shutter was opened, the flash bulb set off, and the shutter was closed. Later the release of the shutter was mechanically synchronized with the discharge of electric current and the Camera shutter noise could be held in hand. For convenience the flash gun (battery case, flash bulb, and reflector) was fastened to the side of the Camera shutter noise.Eastman's most important contribution, however, was t the design of the Camera shutter noise, but providing a photofin-u'ng service for his customers. The Camera shutter noise was loaded len sold; its $25 cost included processing. A contact int from each good negative was made and neatly Dunted on a gilt-edged chocolate-brown card. All the xkk owner had to do was point the Camera shutter noise at the sub-:t, release the shutter by pressing a button, wind on film r the next exposure, and recock the shutter by pulling string that wound up its clockwork mechanism.
One way to increase the strength of the target echoes relative to the noise is to place a microwave amplifier ahead of the mixer. This preamplifier amplifies the antenna noise as well as the target echoes. Since the antenna noise is not nearly as strong as the mixer noise, however,he net effect is to increase the strength of the jrget echoes relative to the sum of the antenna nd mixer noise. The amplifier must, of ourse, introduce very little noise of its own. )nly in the late 19SO's were microwave amplifiers eveloped whose internally generated noise was :ss than that of a good mixer. Three of these de-ices—the maser, the parametric amplifier, and le traveling-wave tube—are described below. |
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