Soundcard Interface for IC 730
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. |
Soundcard Interface for IC 730
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Soundcard Interface for IC 730
On 20 Jun, 04:28, Highland Ham
wrote: ==================================== 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 Thanks. I'll give that a try. |
Soundcard Interface for IC 730
On 20 Jun, 13:34, Postipoika
wrote: 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 Hi Postipoika, Unfortunately, my rig doesn't appear to have a line input, so using the mic connector looks like the only option. I had already planned to use another transformer to isolate the headphone socket on the radio from the soundcard, and an optoisolator on on RTS for PTT, although I may get away with just using the VOX. |
Soundcard Interface for IC 730
wrote in message
... On 20 Jun, 13:34, Postipoika wrote: 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 Hi Postipoika, Unfortunately, my rig doesn't appear to have a line input, so using the mic connector looks like the only option. I had already planned to use another transformer to isolate the headphone socket on the radio from the soundcard, and an optoisolator on on RTS for PTT, although I may get away with just using the VOX. ========= Tom - That is correct, the low-gain or "zero" models (last digit in model number being zero of sold-state late 1970s /early 1980s vintage radios) from Icom (IC-730 being one) ..... did have this problem (pre-amp was in microphone and inside the radio on the input) http://www.heilsound.com/amateur/tips/all_icom.htm You are correct in that you MAY not need the voltage divider -- having an adjustable input such as that with the Jim Mitrenga, N9ART sound card interface "A Flexible Digital-Mode Interface". BTW, although that RadioShack relay is no longer available -- there is an NTE equivalent that is a "drop-in replacement". http://www.farcircuits.net/ http://www.qsl.net/wm2u/images/interface_n9art.pdf w9gb |
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