[Premium-Rx] HF SQUELCH Simple clean audio amp)

[dd3ly at arcor.de]

Hi,

several years I have built a Multi-Input-HF-Squelch-Gate the following way:

- each input splitted into two channels: The audio channel (via a simple OP-amp) and the noise channel (derived from the audio signal via a OP-amp-highpass filter)

- both signals were given to their own fast OP-amp-detector

- the DC-levels coming from the two detectors were given to comparator (which had a hysteresis and a time constant)

- the comparator switched to audio channel to a multi-input audio-amplifier.

This board had six or eight inputs, built with quad-OP-amps. It used a single Euro-card with balanced dc-supply. I was used for surveillance of several receivers by one operator who was eavesdropping several channels. LEDs switched by the coparator output showed the operator which receiver might have an interesting signal. He could select the sum signal to switch it to the autio amp or the single signal.
All this is a long time ago. An up to date solution would use a DSP-channel for each receiver which suppresses sigle tone (CW) and multitone (RATT, RTTY) carriers...

73 from DL
de
Andreé