Encyclopedia of radio electronics and electrical engineering / Civil radio communications
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Many manufacturers of communication equipment serially produce remote desktop speakers for base radio stations, the so-called Desktop Speaker. They differ from the usual ones in that their amplitude-frequency response is limited by the frequencies of the speech spectrum. This significantly reduces the level of high-frequency noise, increases the intelligibility of information. These speakers make working on the air really pleasant and comfortable. Unfortunately, these "speakers" are relatively expensive and out of reach for most radio amateurs.
The recommendations below will allow you to make a high-quality remote desktop loudspeaker for almost any radio station at minimal cost.
The Russian industry mass-produces the head of the electrodynamic type 25GDN-3-8. It provides (according to the passport) an effective operating frequency range limited by the band 50 ... 5000 Hz. and a maximum noise power of 25 watts. The dimensions of the head are the best fit for the basic loudspeaker (diameter 125 and height 76 mm). Within a month, a loudspeaker based on such a head was operated by the author together with a civilian radio station of the Dragon SS-485 brand and showed excellent results.
Structurally, the loudspeaker can be arranged in a metal case made of two U-shaped metal plates. True, in this case, care must be taken to ensure the absorption of the rear radiation of the loudspeaker. To do this, sound-absorbing material should be placed on its back side. The "speaker" case can be made from other suitable materials.
If desired, you can place a low-frequency amplifier with an input switch and a switchable additional filter in the speaker cabinet.
Author: S. Gorlenko (RV3AQW)
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