CIRCUIT DESCRIPTION

I 1. Overview

This transceiver is an 800MHz-band (TK-9401, 9OOMHz-band (TK-941) EFJ LTRrM trunked-system- compatible FM transceiver that can be programmed to operate on both LTR and conventional systems.

2. Circuit Configuration by Frequency

The receiver I S a double-conversion superhet with a first intermediate frequency (IF) of 45.0375MHz (TK- 940), 39.0375MHz (TK-941)and a second IF of 455kHz. Incoming signals from the antenna are mixed with the local signal from the PLL to produce the first IF of 45.0375MHz (TK-940), 39.0375MHz (TK-941).

This is then mixed with the 44.5825MHz (TK-940), 38.5825MHz (TK-941) second local osclllator output t o produce the 455Hz second IF. This is detected to give the demodulated signal.

The transmit signal frequency is generated by the PLL VCO, and modulated by the signal from the micro- phone. It is then amplified by TX amplifier and PA amplifier, and sent to the antenna.

I

 

 

 

 

CF

 

 

ANT TK-940

TK-941

 

455kHz

 

 

TX

806-825MHz

TX

896-902MHz

 

 

 

 

 

851-870MHz

 

935-941MHz

 

 

 

 

RX

851-870MHz

RX

935-941MHz

 

 

 

 

 

 

 

1st MIX

MCF

 

 

 

ANT

RF

 

 

 

 

AF

 

SW

AMP

 

 

'IF SYSTEM -AMPSP

A

 

 

45.0375MHz :TK-940

44.5825MHz :TK-940

 

 

 

 

39.0375MHz :TK-941

 

I

 

 

38.5825MHz : TK-941

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

805.9625-824.9625MHz.: TK-940

 

 

 

 

 

 

 

PLL

MIC

MIC

 

 

AMP

--

-AMP

 

- TK-940

TK-941

 

 

 

 

 

 

806-825MHz

896-902MHz

 

 

 

 

 

 

851-870MHz

935-941MHz

 

 

 

Fig. 1 Frequency configuration

3.Receiving System

3-1. RF unit

An incoming RF signal from the antenna terminal

passes through the antenna switch (D19, D20, and D21 are off) and then the bandpass filter (L9). The

signal is ampliked by RF amplifier 024, and passes through the bandpass filter (L6) again. The resulting signal goes to the flrst mixer (021), where it is mixed with the first local oscillator signal output from the frequency synthesizer t o produce the first IF 45.0375MHz (TK-9401, 39.0375MHz (TK-941).

3-2. IF unit

The flrst IF s~gnalthen passes through a four-pole mono~thlccrystal flter (XFI The s~gnal1s ampllfled by flrst IF amplrf~er0 1 6 and goes to the second IF unlt

The second IF unit cons~stsof an IF system IC ( I C ~ ) and the second mlxer, second local osclllator, second IF fllter, and FlV detector, tC7 mlxes the slgnal Input to ~tw ~ t hthe 44 5825MHriiTK-940), 38 5825MHz (TK-

941)second local osclllator output #f the clystal osclilator (X2)to produce the second IF c' '55kk

The 455kHz slgnal then goes throug 55khL ce-

ramic filter CFI, is amplifl

5y the Ilm

ampllfler,

demodulated by the quac

re FM de

or (In the

same IC), and output to tht

elve audlo ,

l p l ~ f ~ e r

Page 26 Page 28
Page 27
Image 27
Kenwood TK-940 service manual RF unit, If unit, MCF ANT AMP If System -AMPSP, Pll Mic Amp
Page 26 Page 28

TK-940 specifications

The Kenwood TK-940 is a highly regarded mobile two-way radio that has earned a reputation for its ruggedness, reliability, and excellent communication capabilities. Designed for professionals in various sectors such as public safety, transportation, and construction, the TK-940 incorporates advanced technologies to meet the demanding needs of users in the field.

One of the standout features of the TK-940 is its robust design, which complies with military specifications for durability. Its construction allows it to withstand harsh environmental conditions, making it suitable for outdoor and challenging work environments. The radio is also equipped with a water-resistant casing, ensuring that it can function reliably even in wet conditions.

The TK-940 operates in the VHF frequency range, providing wide coverage and strong signal penetration. With a power output of up to 110 watts, users can achieve long-range communication, essential for coordinating activities over large areas. The radio supports both analog and digital modes, allowing seamless integration into various communication systems while maintaining high audio clarity.

Another significant feature of the TK-940 is its enhanced audio quality. The radio is equipped with Kenwood's advanced noise cancellation technology, which minimizes background noise and ensures clear voice communication even in noisy environments. The audio output is powerful and adjustable, catering to individual user preferences.

Moreover, the TK-940 supports a variety of signaling options, includingDTMF, MDC-1200, and 2-Tone/5-Tone signaling, facilitating efficient communication. These signaling features enhance interoperability with other communication devices and systems, allowing users to communicate seamlessly with teams or dispatch centers.

Kenwood has also incorporated user-friendly functionalities into the TK-940. It boasts an intuitive user interface with programmable buttons, enabling quick access to essential features. The large, backlit display provides clear visibility and is easy to read in various lighting conditions.

The TK-940 is designed with safety in mind, featuring emergency alerts and lone worker protection, ensuring users can communicate their status in critical situations. Overall, the Kenwood TK-940 is a powerful and versatile mobile radio that combines durability, advanced technology, and user-friendly features, making it an ideal choice for professionals who require reliable communication in the field.
Top Page Image Contents