Uniden PC-404 40-CH FM Transceiver

Specifications

General

• Frequency Control: Phase Locked Loop (PLL) Synthesized Circuit
• Frequency Coverage: CH 1-40 26.965 to 27.405 MHz
• Microphone: Plug-in Dynamic Type, 600 ohm
• Operating Voltage: 13.2V DC Nominal (Positive or Negative ground)
• Semiconductors: 27 Transistors, 22 Diodes, 5 I/C's
• Internal Speaker Impedance: 8 ohm
• External Speaker Impedance: 8 ohm
• Size: 160 mm (W) x 55 mm (H) x 217 mm (D)

Transmitter

• RF Output: 4W
• Modulation: FM
• Emission Type: F3
• Frequency Tolerance: ±600 Hz Maximum
• Output Impedance: 50 ohm, Unbalanced

Receiver

• Sensitivity for 20 dB S/N: 1 µV Nominal
• Selectivity: 6 dB at 6 KHz, 60 dB at 10 KHz
• Intermediate Frequency: Double Conversion: 1st 10.695 MHz, 2nd 455 KHz
• IF and Image Rejection: 70 dB Nominal
• Audio Output (Nominal): 1.5 W at 10% T.H.D.

Licencing Conditions

The model PC-404 is designed to operate under PTT rules and regulations. Operation of this unit is not permitted until you have obtained the necessary licence to allow use on the permitted 27 MHz C.B. frequencies.

Channel Frequencies

Description

The PC404 is an all transistor 2-way radio transceiver suitable for mobile operation. A frequency synthesizer circuit provides 40 crystal controlled PLL transmit and receive channels in the 27 MHz band, engineered for trouble-free performance. Current drain on 12 volts D.C. is exceptionally low and operation over long periods is feasible even with your engine turned off.

Receiver

The receiver is a sensitive and highly selective dual-conversion superheterodyne type, providing crystal controlled PLL operation on all 40 C.B. channels. The circuit incorporates a number of features designed to provide optimum reception. A ceramic filter provides sharp selectivity and high adjacent channel rejection. As a result, transmissions on adjacent channels cause minimum interference. A variable squelch control is incorporated to silence the receiver when no signals are received.

Transmitter

The transmitter offers crystal-controlled operation on all 40 C.B. channels. 4 watts of R.F. power is the legal limit for the Citizens Band Service.

Operating Instructions

1. On/Off switch and Volume control: Clockwise rotation of the control knob will produce an audible "Click" which will switch on the unit. Further clockwise rotation will increase the output from the speaker.
2. Squelch Control: Used to quiet the receiver during the absence of signals. The squelch control should be slowly rotated in a clockwise direction to the point where noise in the loud speaker disappears.
3. Channel Selector: This rotary switch selects one of the 40 channels for transmit and receive operation.
4. Channel Indicator: L.E.D. Display indicates the channel selected by the 40 position rotary switch (3).
5. Mic Gain: This control is used to adjust, as required, the microphone input sensitivity for optimum amount of modulation during transmission.
6. R.F. Gain: This control is used to adjust the sensitivity of the receiver section. Clockwise rotation will increase the receiver sensitivity.
7. P.A./C.B. Switch: Connect an 8 ohm loudspeaker to the P.A jack (17). The public address amplifier operates when the switch (7) is in the P.A. position (pushed in): speech in the microphone is amplified and heard in the P.A. loudspeaker. For radio communication the switch should be set to its C.B. position (out).
8. Hi-Low Tone Switch: With the switch in the Low position (out) treble is attenuated.
9. Dimmer Switch: This switch is used to adjust the brightness of the LED channel display and the meter. DIM position reduces brightness.
10. S/RF-MOD Switch: This switch is used to select the mode of the meter. In the S/RF position, the meter shows relative transmitter R.F. output Power, and input signal strength when receiving. In the MOD position, the meter shows the level of modulation when transmitting, also shows input level of P.A. amplifier when P.A./C.B. switch (7) is in the P.A. position.
11. Power Meter: The meter is a multi-function meter. It indicates the relative R.F. output, the strength of the incoming signal in S units, and the modulation level or P.A. level.
12. R.X. Indicator: Light Emitting Diode (L.E.D.) which indicates the mode of operation. It indicates green for receiving.
13. T.X. Indicator: Light Emitting Diode (L.E.D.) which indicates the mode of operation. It indicates red while transmitting.
14. Microphone Socket: Connection of the microphone is via the socket at the side of the transceiver. On the microphone there is a pushbutton for switching between transmit and receive, a so called Push-To-Talk switch. NOTE! The switch must not be operated if there is no suitable antenna connected to the socket (16). Otherwise the transmitter can be damaged. To transmit: push in the PTT switch and speak in a normal voice into the microphone, 5-10 cm (2-4 inches) in front of your lips. When the PTT button is released the transceiver goes back into receiving. In the transmit position the T.X. L.E.D. (13) lights up.
15. Power Socket: This transceiver can be connected to a 12 V system with negative as well as positive ground. Most cars use negative ground, but it is easy to verify which one of the poles of the battery is connected to the chassis.
16. Aerial Connector: Connect a suitable aerial especially designed for the C.B. band to connector (16). The aerial and its feeder cable should be of 50 ohms impedance. DO NOT OPERATE THE TRANSCEIVER IN THE TRANSMIT MODE WITHOUT A SUITABLE AERIAL CONNECTED. FAILURE TO COMPLY WITH THIS WILL RESULT IN DAMAGE OCCURRING TO THE TRANSISTOR CIRCUITRY WITHIN THE TRANSCEIVER.
17. External P.A./Speaker Jack: An external 8 ohm 4-watt speaker must be connected to the P.A. SPKR jack located on the rear panel when the transceiver is used as a public address system. The speaker should be directed away from the microphone to prevent acoustic feedback. Physical separation or isolation of the microphone and speaker is important when operating the P.A. at high output levels.
18. External Speaker Jack: The External Speaker is used for remote receiver monitoring. The external speaker should have 8 ohm impedance and be rated to handle at least 4.0 watts. When the external speaker is plugged in, the internal speaker is automatically disconnected.

Installation Instructions

Mounting

The transceiver may be mounted to the underside of the dashboard of a car, truck etc., using the special bracket provided. Always mount the unit to enable the controls to be readily accessible, but in a suitable position that is least likely to cause injury in case of collision. Attach the bracket to the underside of the dashboard using the self-tapping screws supplied. Attach the transceiver to the bracket using the two knurled securing screws provided and tilt the unit to the most convenient angle before tightening.

Power Connection

The transceiver is designed to operate from a battery source of 12 volts D.C. It may be installed on a vehicle employing a positive or negative earth system. The fused D.C. power cable supplied is used to make the necessary power connection to the transceiver. The Red lead (with inline fuse holder) is connected to the positive (+) side of the electrical system. The Black lead is connected to the negative (-) side of the system. In a negative earth vehicle connect the Red lead to a suitable terminal on the fuse box or the accessory wire on the ignition switch. Connect the Black lead to a suitable metal section of the car body. In a positive earth vehicle connect the Black lead to a suitable terminal on the fuse box or the accessory wire on the ignition switch. Connect the Red lead to a suitable metal section of the car body. The transceiver draws a maximum current of 2 amps, thus connection is satisfactory to the accessory or radio terminal on the ignition switch. Connection at this point will ensure the power is automatically cut off to the transceiver when the ignition key is removed.

Microphone Bracket

Attach the microphone bracket provided in any convenient location.

Microphone Connection

Insert the 4-pin plug at the end of the coiled lead into the microphone socket of the transceiver (13).

Antenna Installation and Connection

To enable the PC-404 transceiver to be used, it will be necessary to install a suitable antenna on the vehicle. Due to the many types of antenna available for 27 MHz C.B. operation, specific details of installation are impracticable. There are a wide variation in the type of antenna available, also many different attachments to enable temporary or permanent mounting of the antenna to the vehicle.

When selecting an antenna please remember the following points:

• It must be designed for use in the 27 MHz C.B. frequencies.
• The antenna and its feeder cable must be of 50 ohms impedance.

After a suitable antenna has been installed on the vehicle and connected to the antenna socket (15), it is essential that it is correctly adjusted to ensure optimum performance is obtained. For adjustment, an S.W.R. (standing wave ratio) meter is required to be connected in line with the antenna lead. With the transceiver switched on, select a suitably clear channel, preferably between 18-22, and push the PTT button on the microphone. Following the manufacturer's instructions for the S.W.R. meter, a reading of the S.W.R. will be obtained. Slight adjustment to the length of the antenna may be required to achieve the lowest reading possible on the S.W.R. meter. (Any adjustments made to the antenna should be made with the transmitter switched off).

After the length of the antenna has been altered to achieve the lowest reading on the S.W.R. meter (any figure lower than 1.4 is satisfactory), repeat the S.W.R. measurement on channels 1 and 40 to ensure they also give a satisfactory reading. If at any time during the S.W.R. measurement a result of 3:1 is achieved, immediately release the transmit button, otherwise damage may occur to transistor circuitry within the transceiver. If a satisfactory S.W.R. measurement cannot be obtained, points to check are: Ensure the antenna being used is designed for 27 MHz operation. Any surplus cable to the antenna should not be coiled in a neat coil but left unevenly distributed, e.g., under the rear seat.

Schematic Diagram

A schematic diagram of the Uniden PC-404 is provided, detailing the electronic components and their interconnections.