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1-3 of 3 messages
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Icom interface question
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by KU4UV on August 3, 2009
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Hello again guys,
I have another question regarding my interfacing of an Icom 718. I am using the 13-pin DIN ACC1 connector on the back of the transceiver to feed audio and the PTT function into the transceiver. I am using pins 11(MOD) and 2(Ground) for the audio input. I am using pins 3(SEND) and 2 (Ground) for the PTT line. The transceiver is being keyed using the serial RTS line on the computer.
My question regards adjusting the audio levels going into the transceiver for such things as PSK31 and the digital modes. I also use a contest voice keyer software program that I downloaded for free. Since you can't adjust the MIC GAIN controls for audio, as the the ACC-1 jack is being used instead of the MIC connector, how do I need to go about adjusting the audio level into the transceiver?
I am guessing you just increase or decrease the volume control slider on the computer until you achieve the power output in Watts that you are looking to operate at, while still keeping the ALC from registering? I have the audio slider all the way up, but I am only seeing about 1 Watt of power output when using PSK31 mode. Could I be doing something wrong? Do I need some way of amplifying the audio going into the transceiver? I have one of the external audio amplifiers that Radio Shack sells. This is the audio amp that uses the 9V battery and has a built-in amplifier and speaker. Should I use something like this to increase the audio going into the transceiver, as I don't have a soundcard with any audio amplification to it on my computer. Are there any potential dangers to the transceiver by doing this? Any advice or tips would be appreciated. Thanks gang!
Mike KU4UV
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RE: Icom interface question
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by AA4PB on August 3, 2009
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The sound card is capable of supplying plenty of audio level for the MOD input on the ACC connector. Open the sound card mixer controls and adjust the volume and WAV controls for the desired power ouput (always with the radio's power control turned full up and the compression turned off).
If you can't get enough drive then whatever interface you are using probably has too much attenuation. It may have been designed for driving the very low levels of the microphone input. Some interface units have a level control pot inside. Others may require you to change some resistor values. The MOD input impedance is 10K so if your interface has a 600 ohm or so resistor across the output you may need to change it to something around 10K to increase the output voltage.
Adding any kind of external amplifier is asking for trouble (hum, noise, poor IMD). The sound card has plenty of output capability all by itself.
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RE: Icom interface question
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by K4FX on October 17, 2009
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You may have the connection reversed from the sound card, (feeding the mod with the shield in place of the tip connection) actually the output of the sound card is many times more than the input of the radio needs, connected properly you will need an attenuator circuit between the sound card and the rig to bring the levels down to an acceptable level. You are correct about using windows volume control to set the output.
If your rig has an RTTY keying input on it, (I think it does) you can make your RTTY setup a lot simpler with just an NPN transistor and a 1K resistor. It can be found here http://www.aa5au.com/rttyinterface.html Works as well as a Rigblaster Plus or Pro for a RTTY keying at a faction of the cost! No adjustments to make and you will have a nice clean signal!!
73
K4FX
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