S meter

Since many amateur receivers are fit- tedwithanSmeterthatfunctionsfar from logarithmically, the proposed circuit should be a welcome exten- sion of such receivers. Although ICs such as the CA3089 or the CA3189 are not in common use any more, they serve a useful pur- pose in the meter circuit, because, apart from a symmetric limiter, a coincidence detector, and an AFC amplifier, they contain a very good logarithmic amplifier-detector. As is seen, the circuit is fairly simple, but remember that these ICs operate up to about 30 MHz, so that the wir- ing of the meter, and also its connec- tions in the receiver, should be kept as short as possible. Note further that • the input of the CA3189 must be terminated by 50 Q; • the connection to the input of the 1 2 o7 (.3 O 6 5 2 Ub = 12V 10 100 1k 10k 100k INPUT SIGNAL • pv • if it is not possible to obtain the in- put signal from a low-impedance S meter 221 12V<40mA CA3189 should be in screened cable; source, a source follower shou...