ELECRAFT KAF2 Instruções de Operação descarregar pdf (Página 5)

Page 5

Construction Manual for the K2DI v.III and K2DI-PCI boards © EA3BLQ - Revision June 2005

Cutting the Front Panel mike connector's AF and PTT lines and muting the

AF amplifier, when transmitting data:

Due to its low current drain and its switching features, I've chosen the use of a CD4053BE

CMOS Analogue Multiplexer to cut and commute the AF and PTT lines from the Front Panel

Microphone Connector, through J1, to the Rear Digital Connector when transmitting data,

and to disconnect U2, the audio amplifier LM386, from the product detector by grounding

the gates of Q1 and Q2, following Elecraft's design.

K2DI STANDBY (Receive) POSITION

The K2DI circuit schematic (see page 29) shows the device in its standby (receive)

position, by default, the multiplexer mosfets are biased high due to pins 9, 10 and 11 of

U1, CD4053BE CMOS, being fed with 5V DC through R3 (a 10K resistor). In this way we

have:

a) The ground connected at pin 14 of U1 (a) goes nowhere as pin 13 has no connection.

b) The outgoing microphone signal from the AF pin at J2 goes to the AF pin in J1 through

pins 15 and 1 of U1 (b), as both AF pins are contacted in parallel, and

c) The signal from the PTT pin at J1 goes to the PTT pin at J2 through pins 4 and 3 of U1

(c), connecting the PTT pins in parallel too and thus enabling the Front Panel AF and PTT

lines.

Because of the DC component (2.5 V fed through R1 and R2) present in the U1 (b), three

10 µF electrolytic capacitors (one inlet and two outlets of U1) are needed to decouple the

DC from the signal.

K2DI DIGITAL TRANSMIT POSITION

When, because of data transmission, the PTT is keyed through the Rear Data Connector or

by means of the K2DI-PCI Serial or Tone (VOX) circuits, pins 9, 10 and 11 of U1,

CD4053BE, are grounded through pin 3 at J3. Then the voltage at those pins drops to 0 V.,

setting the multiplexer mosfets low and thus three switching operations are activated:

1) U1 (a) - Switches pin 14 from pin 13 to pin 12 and grounds the gates of Q1 and Q2,

setting them low and thus disconnecting the AF amplifier.

2) U1 (b) - Switches pin 15 from pin 1 to pin 2, connecting the outgoing digital signal

received from the computer’s soundcard through pin 1 of J3, and coming from pin 1 of

the MiniDIN connector or from pin 1 of P1 at the K2DI-PCI board, to the AF pin at J1 and

thus to the K2 TX circuitry. The unwanted mic signal coming from the AF pin at J2 (if

any) is cut and has no way out.

3) U1 (c) - Switches pin 4 from pin 3 to pin 5, keying the rig by grounding the PTT pin at J1

and disconnecting the microphone PTT line at J2

CAUTION:

• Avoid triggering the K2 PTT through the KI/O2 by means of a program’s CAT

facility. If you do, the K2DI v.III WILL NOT be activated and the Digital

transmission WILL NOT take place.

1 2 3 4 5 6 7 8 9 10 ... 31 32

Sem comentários

ELECRAFT KAF2 Instruções de Operação Página 5