ProData Sound Card Interface
For Icom Rigs
The Completed Interface
The ProData Printed
Circuit Board
A Quality Sound Card Interface for ICOM Rigs as described in the March 2002
QST, page 31.
- Op-amps in the receive and transmit audio chains to ensure ample signal strength from
low-level ACC(1) signals.
- Logic controls guarantee that receive and transmit audio paths can never be open at the
same time. This lets users listen to the transmit audio throught the radio's transmit
monitor without incurrng feedback, even if the sound card loops its input throught to its
output.
- Analog gain controls on the front panel of the interface provide smooth, easy adjustment
of levels while viewing the radio's panel meter and the digital mode software display.
It's quite inconvenient to adjust software sliders with a mouse, especially given the
coarse resolution of most on-screen controls. It's also inconvient to switch back and
forth between the operating program and the sound card mixer program while making
adjustments. With analog gain controls in the interface, the sound card mixer controls can
all be set center scale and forgotten. All adjustments are made with "real"
controls on the front panel of the interface.
- Power for the interface is provided by the transceiver's 13.8-V dc supply via the ACC(1)
connector.
- A front-panel switch turns the interface on or off and an LED indicator displays the
status of power and PTT.
- Two identical eight-pin DIN connecors on the rear panel of the interface provide a
pass-through of all leads to the second connector when the interface is not in use. This
provides a place to connect other accessory devices such as TNCs, hardware controllers,
etc.
- The transceiver signal lines not needed by the interface (RTTY, SQLS and ALC) are always
passed through to the second DIN connector where they are available for use even if the
interface is enabled.
- A reliable Sound Operated Xmission (SOX) circuit controls the transceiver's PTT circuit
without the need to tie up another computer serial port.
- An optically isolated PTT circuit and a switch to disable the SOX are available for
those who are still convinced that the serial port is the best way to handle T/R
switching. This circuit is fully compliant with the RS-232 specification for voltage and
impedance.
- Plenty of excess PTT keying capacity is available. The PTT keying transistor will handle
a maximum open-circuit voltage of +60 V and a closed-circuit current of up to 450 mA. The
maximum closed-circuit voltage drop is 0.4 V.
- Balanced, ground-isolated inputs and outputs for all computer connections guard against
hum and noise sometimes caused by equipment grounding differences.
- Telescoping shields on all computer connections provide excellent RFI protection while
eliminating the possibility of ground currents flowing in the shields. Telescoping shields
are grounded at the interface end and not connected at the computer end.
- RFI filters on each lead entering or exiting the interface guard against RF getting into
the circuitry.
- A single cable connection is used between the interface and the transceiver's ACC(1)
connector. There's no "rats nest" of leads to connect to the transceiver.
ProData Construction Information
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