RadioBanter - View Single Post

Postipoika · June 20th 08, 01:34 PM posted to rec.radio.amateur.homebrew

Highland Ham kirjoitti:
wrote:
I am currently building a radio - sound card interface for my IC-730
so i can use PSK31. AIUI, the mic that came with the rig contains a
preamp, so presumably the radio is expecting an audio level above a
usual mic. Does this mean I can simply use the audio level from the
sound card straight into the Mic input on the radio via a 1:1
transformer for isolation, with no need for a voltage divider to bring
the level down?

Thanks.
====================================
Transformer does not need to be 1:1 exactly
Suggest you include an approx 1000 Ohms trimpot to fine adjust the mic
port input from the transformer. Assuming the radio audio input
impedance is in the order of 500 Ohms.

Frank GM0CSZ / KN6WH

Please note that a single trafo only in mic line doesn't isolate
satisfactory.
Otherwise there will still remain humming earth loops.

If your rig has a phone patch or a line input it is preferred to use
these. You need not to play with plugs .
In many rigs the VOX is not controlled via line input. In that case PTT
rules on the air.

Be ready to use a trafo also in headphone output line and a relay or an
opto isolator for PTT.

It is most simple to use COM port RTS or DTR for PTT.
KISS: Connect a high bright led and a 5V dil relay in series directly
into RTS. Led is very nice to show "On the Air".

postipoika