The COV21TX and the companion COV21RX are small self-comprehensive automatic changeover equipment to be used as signal
front-end module in couple with 2 STL Transmitters and Receivers of the SIELCO’s EXC/RTX19 family to make a simple high
reliable 1+1 system. COV21TX is intended as changeover unit for small FM Transmitters/Exciters up to 30W or for STL
Transmitters up to 10W / 2500MHz. COV21RX makes the same for Receivers in the same frequency range. The reserve apparatus
is configured in hot stand-by and switching with the main one takes less than 500ms to be operative from the failure detection.
The apparatus comprise all internal passive switches for HF and LF signals and a simple but effective control logic. They directly
mate with the Transmitters or Receivers and take advantage of the intelligence and the alarm logic present on the base equipment.
Being signal switches purely passive and the internal control logic very simple, they are extremely safe and remain active even in
case of catastrophic logic failure or loss of power supply (transmitter changeover only). The power supply is derived by the
+24Vdc battery input/output of the STL equipment and is inherently redundant, avoiding adding internal mains power supply for
an improved reliability. The version specially suited for FM Transmitters incorporates its own power supply.
Instead of making a simple passive splitting of the RF signal so resulting in some 4dB sensitivity worsening, the COV21RX
incorporates a very low-noise preamplifier with a skirt low-loss input filter so dramatically improving the already good input
sensitivity of the RTX19 Receiver and permitting to achieve very narrow band filtering (few MHz up to 2500MHz) without
impairing the intermodulation characteristic of the single Receiver.