Universal PTT for digital communications using a sound card
Valid for JVCOM32, CHROMAPIX, PSK31 and all the programs suprting a sound card.
At present, nearly all the programs
used in amateur digital radio communications (JVComm32, ChromaPIX, etc.) feature
the option to choose which pin (DTR or RTS) from the communication port is
to activate de PTT and thus toggle the rig into transmission.
One of the features of this circuit is that , to match the settings of the program, you can also choose the most suitable pin (DTR or RTS) via hardware, by positioning jumper JP1 in the required setting.
The voice/auto toggle, when in voice position, will activate the PTT and will allow you to talk with your correspondent by using the electret microphone, normally accompanying the sound card, or even a dinamic mic. To transmit data, images, etc., the toggle is to be positioned in auto. In any case one LED will glow to indicate that you are transmitting.
The preamplifier is designed to be used with an electret or dinamic mic, as stated above, and uses only one transistor to amplify the signal. The amplified signal feeds the variable resistor (RV1) which will allow the adjustment of the voice level.
SOUND CARD'S INPUT-OUTPUT
Connector RCA1 is to receive the
outgoing signal from the Line Out (or Spkr Out) outlet of the sound card.
The signal feeds resistor R9 and, passing through condenser C9, goes to RV2
and to the input pin of the transceiver. RV2 regulates the signal level finally
RCA2 sends the incoming signal to the Line In connection in the sound card. Trim pot. PT1 allows the setting of the luminance level in the images received from the weather satellites and has no effect on other modes (SSTV, FAX, PACKET )
Connections with the transceiver or eventually with the receiver of weather satellites are made through one 5 pin DIN 180 connector using the pin setting normally found in equipment like TNC, HARIFAX etc.
SALVADOR ESTEBAN MUÑOZ
GUIPUZCOA, 37 ATICO 3