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Cerca per tag : versatile interfaccia IW6DFW


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A versatile radio PC interface designed by IW6DFW Maurizio Malaspina

Inspired by the “Tone Keyed Sound Card Interface (Alternative design using opto-isolator output) [Rev 2]” published by Stephen H. Smith WA8LMF on 7 April 2003, I’ve designed the simple, cheap and home-brewable DIGIVOX interface documented in this paper.

The purpose of this project was to realize a simple to employ board able to connect, both handhelds and base station/vehicular rigs, to the audio board of a PC to easily start with digital communications at low-cost and reduced resources commitment.

All these preliminary requirements led to DIGIVOX (refer to schematic 1) with the following features:

· Power supply: 9÷13.8V DC (usually the same of the rig or a 9V battery).

· Galvanic insulation to and from PC audio board (2 x 600Ω 1:1 audio transformers)

· Selectable PTT handling mode between two settings:

o VOX: PTT is managed directly by the audio out signal of the audio board so no dedicated additional PC port is required. A long/short hang time up to about 100ms is settable via jumper to permit slow CW operation.

o UART: classical old style mode that requires a connection to a dedicated UART PC port. Note that, in this mode, the software must be able to handle this driving signal.

In every PTT operating mode, the coupling between the PC driving signal and the PTT input command of the radio is electrically isolated (either by opto-coupling or galvanically, as already mentioned).

Also a “transmission in progress” red led indicator permits the operator to check the communication status.

· Selectable PTT technology depending on rig: an RC network and a bypassable pure resistive attenuator network permit to connect to the PTT of an handheld radio (like my IC-E90) and fine tune the audio level of the signal entering the rig port, to prevent apparatus damaging. Alternatively it’s possible to connect a base station rig acting directly on its PTT pin. The configuration is selectable via dip switches.

To realize the interface I suggest to build the PCB (I’ve manufactured it using press-and-peel technique), using the 1:1 scaled master of Figure 3. Then all the THT components listed in BOM (Table 1)has to be soldered to get something similar to the the preview shown in Figure 1. Subsequently it’s necessary to realize seven wired links, like the ones shown in Figure 2.

All the necessary connections are reduced to a custom DB25 terminated cable that will connect DIGIVOX CON1 and on the other end to the rig and the PC using customized connection (jacks), and two power supply cable directly screwed on CON2.

Once the PC will be connected to the rig by DIGIVOX interface, setup it following the instructions of Table 1 to configure the DIGIVOX wished operating mode, then power up the system and run your favourite radio digital communication software to perform some tests.

If all is ok, welcome to the digital ham radio world and see you on air! Otherwise don’t esitate to contact me by e-mail.

Maurizio M., IW6DFW


 

Schematic 1: DIGIVOX with DB-25 pinout table


DIGIVOX - Bill Of Materials

Item

Q.ty

Part reference

Value

Package/Note

1

2

T1 T2

 

600Ω 1:1 audio transformers

I used a Victory manufactured model, but any transformers with the same electrical parameters will works well (eventually adapt it mechanically to the footprint in the PCB using four pieces of a proper sized coppered wire )

2

1

U1

LM158

DIP-8

3

1

U2

4N25

DIP-6

4

2

D1 D2

1N4148

DO-35

5

1

D3

RED LED

THT 5mm

6

1

R1

1.5kΩ 5%

THT 1/4W

7

2

R2 R4

1.8MΩ 5%

THT 1/4W

8

1

R3

1MΩ 5%

THT 1/4W

9

2

R5 R7

3.9kΩ 5%

THT 1/4W

10

1

R6

LINEAR TRIMMER 470Ω

HORIZONTAL (1 TURN)

11

1

C1

1nF Low voltage - POLY

THT

12

1

C2

150nF Low voltage - POLY

THT

13

1

C3

10uF 16V - ELECTROLYTICS

THT

14

1

JP1..7

STRIP 1x17 (4pcs 1x2 + 3pcs 1x3)

THT 100mils (2.54mm) pitch

15

1

CON1

DB25 FEMALE CONNECTOR

PCB TYPE 90° GROUNDED

16

1

CON2

2 POLES LOCKING SCREW FLANGES CONNECTOR

THT - 90° - 200mils pitch (5.08mm)

Table 1: Bill Of Materials


Figure 1: Assembled board preview (TOP VIEW)

Figure 2: Only wired link to realize showed in red (TOP VIEW)

Figure 3: PCB master TOP side 1:1 (TOP view)

Figure 4: the first prototype

 

Table 2: configuration table

JUMPERS SETTING

MODE

JP2 OPENED

JP4 OPENED

Attenuation net is composed by R5 and R6 series. Suggested for radio which accepts only low level input signals. Refers to your radio manual.

JP2 INSERTED

JP4 OPENED

Bypass R5 to reduce the resistance of conductive path wich connects “LINE OUT” signal to radio “AUDIO TO TX” signal. In this way the trimmer R6 is the only attenuator activated.

JP2 INSERTED

JP4 INSERTED

Attenuator deactivated, “LINE OUT” is directly connected to “AUDIO TO TX” signal.

JP5 POS. 1-2

JP7 INSERTED

In this mode C3 and R7 circuit provides a “PTT+AUDIO_IN” signal to drive many handheld rigs. JP7 links “AUDIO RADIO GND” signal with “PTT RADIO GND” signal (needed for correct operation).

JP5 POS. 2-3

JP7 OPENED

Enable classic PTT command mode: optocoupler implements a “PTT OPEN COLLECTOR” signal.

JP3 POS. 2-3

JP6 POS. 2-3

Enable VOX circuit to generate PTT command.

JP3 POS. 1-2

JP6 POS. 1-2

In this way PTT signal must be asserted by serial port or parallel port (by software).

JP1 INSERTED

Enable VOX long hang up time. Required for transmissions with long intersymbol signal blank (like slow CW an others emission modes).

JP1 OPENED

Set VOX normal hang up time ( For example used by AX.25 and SSTV transmission

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