A developer and producer of stereo equipment and audio electronics, Kenwood has long been a leader in its industry. In 1981, the company built the first ever audio/video amplifier for home theatre. Kenwood then went on to create, among other inventions, the first antitheft car cassette deck that could slide out of the dash. Over the years, many of Kenwood's technology innovations have been adopted by other companies. Kenwood has been manufacturing tuners for many years; among its offerings is the KT-990D. A black digital tuner, this popular model was first introduced by Kenwood in 1988.
Front Panel Controls
On the front panel of the KT-990D tuner is an active reception switch that switches between manual and automatic selection of IF (intermediate frequency) and RF (radio frequency) settings. An RF selector that switches between distant and local is also featured, as well as an IF switch to select wide or narrow bandwidth and a high/normal level switch. Also included are a stereo or mono switch, a program switch, an AM or FM switch, an automatic or manual tuning mode switch and an A/B memory system offering a total of 20 preset channel choices.
Found on the rear panel of the KT-990D are options for tuning the unit. The tuner features 50 or 100 kHz spacing for FM channels and 9 or 10 kHz spacing for AM channels. Tuners available with the special spacing option have the ability to tune in 25 kHz increments. For spacing changes to take effect, the switch on the rear panel must be flipped; the tuner should then be turned off and turned back on again.
Gangs and Filters
The KT-990D tuner has the electronic equivalent of five gangs. Since two of these are in its local oscillator, however, it actually utilises four gangs by the traditional method of counting. These four gangs give the KT-990D tuner respectable image rejection and overload protection. The KT-990D has two ceramic filters and an LC filter in the wide IF bandwidth mode; in the narrow IF mode it has three ceramic filters.
The KT-990D has a Direct Loop Linear Detector (DLLD), which is Kenwood's version of a phase locked loop detector and is only seen on top-performance tuners. Its "direct pure" linear multiplying circuit has a MC1495L four-quadrant multiplier doing the MPX work. Also featured on this tuner is a distortion cancellation circuit that generates a signal to cancel distortion. This cancellation signal is mixed with the signal that corrects IF filter nonlinearities.