Kenwood TKR-840 Service Manual

Also see for TKR-840: Brochure & specs Instruction manual

TKR-840 OPERATING FEATURES106. Simplex/Duplex OperationThe Simplex/Duplex function is used to specify whether thechannel is used as simplex (receiver muted during transmit)or duplex (receiver unmuted during transmit). The channel hassame TX/RX frequency and can operate only in Simplex mode.7. Repeater/Base Station OperationThe Repeat function is used to specify whether the channelis used as a repeater or as a base station. A repeatersimultaneously and automatically re-transmits its receivedaudio; a duplex base station has independent simultaneoustransmit and receive paths; a simplex base station are mutuallyexclusive transmit and receive paths.8. Signalling Feature8.1 Multiple QT/DQTThe TKR-840 can function as a multiple-QT/DOT decode/encode unit for operation as a community repeater or multipleQT/DQT base station. 16 Multi Tables can be created, eachMulti Table consisting of 16 decode / encode combinationsand can be assigned on a per-channel basis.The Multi Table function enables the TKR-840 to decodeany one of the 16 QT/DQTs pre-programmed into the selectedMulti Table. When receiving a signal (repeater operation), therepeater uses the QT/DQT encode which corresponds to thedecoded QT/DQT as set in the Multi Table. In the Multi Table,signalling pair of "No.1" (first column) is defined as "Primary".A receiving signalling (if it is contained within No.1 to No.16) isdefined as "Current".8.2 Encode Tone in MultipleWhen Local mic PTT, Remote PTT or Ext. PTT is activewhile the repeater is in use or the duplex-base station isreceiving, the encode signalling is determined according toEncode Tone in Multiple function. The simplex-base stationalways transmits the "Primary" encode QT/DQT.Current : When any PTT as described above is active whilethe repeater is in use or the duplex-base station is receiving,the "paired" encode QT/DQT associated with receiving QT/DQT is transmitted. When any PTT is active while the repeateror the duplex-base station is in idle period, the "Primary'' encodeQT/DQT is transmitted.Primary : When any PTT (provided that the Priority of anyPTT is higher than the Priority of Repeat PTT) is active whilethe repeater is in use, the encode QT/DQT changes "paired"encode QT/DQT to "Primary" while continuing to transmit.When any PTT is active while the repeater is in idle period, the"Primary" encode QT/DQT is transmitted. In the base station,the "Primary'' encode QT/DQT is always transmitted regardlessof the receiver status.8.3 QT Reverse Burst TimeDuring repeat with QT tones, the repeater re-transmits aphase-shifted burst of the QT tone ("reverse burst") when itdetects the radio using the repeater has un-keyed and alsosent a reverse QT burst (squelch-tail elimination). This mutesa receiving radio's speaker audio before its receiver circuit shutsoff causes squelch tail noise in the speaker audio. The TKR-840 can select the time between 140 to 200 ms that the QTreverse burst is sent. Typically this time should not have to beadjusted from the default value. The transmission of the QTreverse burst can be also inhibited if the QT Reverse Burstfunction is set to "No".8.4 DQT Tum Off Code TimeDuring repeat with DQT codes, the repeater re-transmits aspecific turn-off code when it detects the radio using therepeater has un-keyed and also sent the turn-off code (squelchtail elimination). This mutes a receiving radio's speaker audiobefore its receiver circuit shuts off and causes squelch tail noisein the speaker audio. The TKR-840 can select the time between140 to 200 ms that the DQT turn-off code is sent. Typically thistime should not have to be adjusted from the default value.8.5 Off Hook DecodeThe TKR-840 is able to decode QT/DQT regardless whetherthe local microphone is in the on- or off-hook condition. Whenthe Off Hook Decode function is enabled, the TKR-840 iscapable of QT/DQT decode even though the microphone is inthe off-hook condition (or a local microphone is not installed).9. Scan Feature9.1 Scan OperationProviding that the TKR-840 contains two or more non-priorityADD channel or one or more non-priority ADD channel andPriority channel, it starts scanning once the Scan On functionis executed and displays "SC" on the 7-seg LED. Scanningstops temporarily if any following conditions become valid.1) if a RF carrier and a valid QT/DQT is present. The receivingchannel number is displayed and the received audio is heardfrom a speaker.2) if a RF carrier is present, providing that the Monitor Onfunction is executed.3) if the Squelch Off function is executed. Scanning stops onthe channel being scanned when Squelch Off is executed,the channel number is displayed and the received audio isheard from a speaker.4) if a local microphone's hook is in off hook status, providingthat the Off Hook Scan function is set to Disable. Scanningstops on the Revert channel, but the audio is not heard untila valid signal is received.When the received call is ended, scanning automaticallyresumes after the period set in Dropout Delay Time functionhas expired. When the Scan Off function is executed, the TKR-840 inhibits scanning and displays the selected channel.9.2 Scan Sequence1) Normal Scan : When no Priority channel is set, scanning ofADD channels is done in ascending order.2) Single Priority Scan : The Priority channel is set as either a