A new external receiving modul TRM-2U has been designed on the basis of preselector, low-noise controlled antenna amplifier placed in the weather-proof cabinet (FOTO) under the antenna, the control unit (Fig.2),
placed in the rack with the repeater. The principle possibilities of this product are as follows: low-noise amplification of HF signal within the range from 10 to 1000 MHz (the mode of operation "MIIIY-1" ), the operative transfer to the reserve chip of low-noise amplifier in the case of the fault of the main chip (the operation mode "MIIIY-2"); the direct coupling of receiving antenna to the reduction cable if both chips of the low-noise amplifier are our of order (the operation mode "AHT"). The mode choice is implemented by means of button switch disposed at the front panel of the control unit (Fig.3).
The module TRM-2U provides also the protection of the amplifier input and output against the static potential and high level of HF-power, the continuous control and indication of the amplifier consumption current value, the receiving antenna SWR control without demounting the amplifier, feeding and controlling the antenna amplifier by HF reduction cable.
Such amplifiers are of importance in any trunking and convention systems as well as in the mobile communication systems. Even while using the receiving feeder of high quality at the heights of antenna mounting around 70 m and more the irreplaceable losses from 3dB and more appear in it what significantly impacts the distance of the wireless communications. The amplifier installed immediately under the antenna amplifies the received signal in advance, before it would be lost in the feeder. The noise of the feeder itself remains at the same level and the total ratio Signal-to-Noise in the receiving channel will be just more preferable.