Ten-Tec Corsair modification

Separation of the AGC and RF/IF gain functions in modern transceivers provides improved receiver operation. In a receiver in which the AGC remains on when the RF/IF manual gain control is backed off from the maximum position, SSB reception can be improved by adjusting the gain until the received noise signal is just above the receiver minimum-signal threshold. The Ten-Tec Corsair incorporates separate receiver AGC and manual IF-gain controls.

When operating the Corsair with the If-gain turned down, the S-meter readings for a given signal strength are reduced. In order to obtain meaningful S-meter readings, it is necessary to momentarily turn the IF gain to maximum. This modification provides that

function through the addition of a "momentary" switch as shown in fig. 1.

The switch is a subminiature, normally-open, spring-return push button. To take an S-meter reading the button is depressed shorting the wiper to the top of the control. Due to the excellent AGC characteristics of the receiver, there's no blast from the speaker.

There's a convenient space on the Corsair's front panel for mounting the push button - to the right and above the center of the manual IF-gain control (RF GAIN). Radio Shack subminiature push-button switch No. 275-1571 is a good, if not exact, match for the SPOT push button on the Corsair panel.

This technique can probably be adapted to other transceivers with an AGC function that remains operative over the full range of the RF/IF manual gain control.

Jack Geist. NBBEK

Ham Radio page 62 April, 1984