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Simple sound card interface #ft8

 

I want try my ubitx for digital modes with external usb sound card and usb rs232 cable. Suggest simple interface setup for this. Are audio isolation transformers necessary in audio line?
Mike aka KC2WVB
 

Its been 8 years since I used PSK modulation and I remember that isolation transformers were a good idea but perhaps not absolutely necessary. I think I made a pair for both line-in and line-out. I still have them. At that time nothing else was required for I was using a Kenwood TS-440-SAT which had a jack in the back to use in lieu of the microphone. I also remember that PSK could be obtained by directly placing the computer's speaker against the microphone with the PTT held down so I am thinking that nothing is necessary for PSK beyond using isolation transformers and I don't think things have changed.?

For the other forms of digital modulation that have arrived in the past 8 years I am clueless.

On Mon, May 28, 2018, 11:13 PM Praba Karan <vu3dxr@...> wrote:
I want try my ubitx for digital modes with external usb sound card and usb rs232 cable. Suggest simple interface setup for this. Are audio isolation transformers necessary in audio line?

 

I think it depends on where you tap into the audio out from the rig. I didn¡¯t feel like drilling another hole in my case, so I use the headphone out. To do that, I had to use a low to high impedance transformer. After that, I used a Jfet buffer and a volume pot. For the transmit side I only use a buffer and volume control. Already worked several stations on FT-8 and PSK-31.
Mike aka KC2WVB
 

Wow, you went all out. I just used the volume controls on the sound card and the Kenwood. For the isolation transformers I am pretty sure they are Radio Shack audio transformers with one side being called 8 ohm and the other either 1000 or 500 ohm depending on the taps used.


On Mon, May 28, 2018, 11:32 PM Richie Chambless <rchambless7@...> wrote:
I think it depends on where you tap into the audio out from the rig. I didn¡¯t feel like drilling another hole in my case, so I use the headphone out. To do that, I had to use a low to high impedance transformer. After that, I used a Jfet buffer and a volume pot. For the transmit side I only use a buffer and volume control. Already worked several stations on FT-8 and PSK-31.

 

I bought an el cheapo USB soundcard on eBay, also because my laptop has a combined audio port.
Has been working great for me combined with a USB cable for CAT control.

John
KG5WJQ
 

here's what I did...
/g/BITX20/wiki/Digital-Setup
--

 

Thanks Doug,

I followed your instructions and was able to make several FT8 contacts yesterday. I wonder what the 1K resistors are for across the audio outputs. Can they be eliminated?

73, Dennis
W7DRW

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