Ramsey Electronics FZ-146 Specifications download pdf (Page 83)

FX-146 • 83

ADDITIONAL RECEIVER IC FUNCTIONS AND FEATURES

In addition to audio output at pin 17, a separate high speed data output (up

to 35000 baud) is available and may be linked directly to a packet TNC or

other data controller using the jumper wire pad provided on the PC board.

The MC13135 is capable of detecting true FSK (frequency shift keying) in

addition to AFSK.

The receiver has good "hysteresis" characteristics, the ability to hold the

squelch open once it has been broken by a marginal signal, even if the

signal becomes weaker. The IC also has carrier detect circuitry which is put

to good use in the transceiver design by providing very effective squelch

action. The squelch is activated by signal strength, not by noise. When no

carrier is detected, the voltage at pin 16 is high, which causes Q6 to mute

the audio amplifier U2 as explained in Stage B.

When a carrier is detected, the voltage at pin 16 drops low, turning off Q6.

Resistor R13 permits squelch adjustment.

Finally, the carrier detect circuitry affords the same COR ("Carrier Operated

Relay") action as needed in any repeater, which is why the output is also

available on the PC board, designated "COR." It is up to creative users to

determine their own practical implementations for this feature.

Stage CR ASSEMBLY PROCEDURE:

 CR1. Install U1, the MC13135 24-pin DIP FM Receiver IC. Make sure

all 24 pins are visible through the holes before soldering and be very

sure that the notched end is oriented as illustrated.

Install the following resistors:

 CR2. Install R11, 47K ohm (yellow-violet-orange).

 CR3. Install R5, 10K ohm (brown-black-orange).

 CR4. Install R4, 68K ohm (blue-gray-orange).

 CR5. Install R24, 10K ohm (brown-black-orange).

 CR6. Install R119, 270 ohm (red-violet-brown).

 CR7. Take a moment now to double check your work. Touch up any less

than perfect solder connections.

Install the following capacitors:

 CR8. Install C16, .01 uf disc capacitor (marked .01 or 103).

 CR9. Install C5, .01 uf disc capacitor (marked .01 or 103).

 CR10. Install C9, 4.7 or 10 uf electrolytic, observe correct polarity.

1 2 ... 78 79 80 81 82 83 84 85 86 87 88 ... 144 145

No comments

Ramsey Electronics FZ-146 Specifications Page 83