Connecting a KX2 to a Laptop

[KE1B]

I am trying to connect a KX2 (which has a standard headphone output and microphone input on separate 3.5mm jacks) to a laptop that has an integrated (4 pin TRRS) microphone input and sound output. I have the adapter than converts the 4-pin 3.5 mm jack to two separate jacks, for a microphone input (to the laptop) and sound out (from the laptop). I connected those jacks to the corresponding jacks on the KX2, using stereo cables. This is the exact configuration as shown in Frank Cady’s KX2 book.

On transmit, everything works fine. I can key the radio from N1MM, send CW (via KY commands), and send digital data (e.g., FT8) to the radio and the radio transmits everything fine. All levels can be adjusted to perfection.

On receive, I’ve got nada. I can’t see any audio coming from the radio into the laptop. If I disconnect the external input, I can actually decode digital data with audio from the radio’s speaker, through the air, to the laptop’s internal microphone. Now, I can deal with the differences in levels, if necessary, but I’m not getting ANY audio from the radio to the laptop via the cabling. What am I missing? I’m hoping to make this work without lots of little adapter boxes, USB hubs, external codecs, etc. for very-portable operation.



Rich KE1B

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[Don Wilhelm]

Rich,

Do you have audio out of the KX2 on the headphone jack?  If so, the
other thing to consider is the adapter to the TRRS plug and the audio
levels for Microphone or Line in your computer.  Make sure you computer
does not have the mic disabled.  If windows, check the soundcard
settings - there is something similar with a Mac, but I am not a Mac user.

Recent upgrades to Windows do mute the microphone or line input.

73,
Don W3FPR


On 9/14/2018 11:48 AM, [hidden email] wrote:
>
> I am trying to connect a KX2 (which has a standard headphone output and microphone input on separate 3.5mm jacks) to a laptop that has an integrated (4 pin TRRS) microphone input and sound output. I have the adapter than converts the 4-pin 3.5 mm jack to two separate jacks, for a microphone input (to the laptop) and sound out (from the laptop). I connected those jacks to the corresponding jacks on the KX2, using stereo cables. This is the exact configuration as shown in Frank Cady’s KX2 book.
>
> On transmit, everything works fine. I can key the radio from N1MM, send CW (via KY commands), and send digital data (e.g., FT8) to the radio and the radio transmits everything fine. All levels can be adjusted to perfection.
>
> On receive, I’ve got nada. I can’t see any audio coming from the radio into the laptop. If I disconnect the external input, I can actually decode digital data with audio from the radio’s speaker, through the air, to the laptop’s internal microphone. Now, I can deal with the differences in levels, if necessary, but I’m not getting ANY audio from the radio to the laptop via the cabling. What am I missing? I’m hoping to make this work without lots of little adapter boxes, USB hubs, external codecs, etc. for very-portable operation.

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[KE1B]

Did a little testing, did a little thinking…

First, I verified that the audio output from the KX2 was working; it drove a pair of headphones just fine.

Then I verified that the external mic input to the computer was working; I connected a real microphone and was able to record audio using Audacity.

Then I thought about it, and realized that the KX2 output is STEREO, whereas the computer mic input is MONO. So I tried a MONO 3.5mm cable instead of the stereo cable, and voila! Audio going from the KX2 to the computer, verified by making a couple of FT8 contacts.

Thanks to all that responded.

FYI, this is a real minimal configuration. The “computer” is an Asus Transformer, 1 lb tablet running Windows 10, and the radio is a KX2. I can carry the whole shebang in one hand. Plan to use this with a Buddistick from French Polynesia, going to Moorea and Bora Bora next year. Probably won’t be able to work many NA with only QRP and a Buddistick, but I’ll see what I can do.

Rich KE1B

> On Sep 14, 2018, at 8:58 AM, Jack Brindle <[hidden email]> wrote:
>
> Hey Rich!
>
> What make of computer? Is the port selected for input? If a Mac, the normal selection would be the internal microphone, so you would need to go into the System Preferences/sound panel => Input tabard select the external microphone port.
> Interesting that my MacBook Pro doesn’t show such a port, so I’m not really sure what it takes to get it to show up.
>
> You also posted to the N1MM list, so I suspect you are using a Windows machine. I can’t help you there, but look for some sort of input port sound selection.
>
> Hope you get the issue solved quickly!
>
> 73,
> Jack, W6FB
>
>
>> On Sep 14, 2018, at 8:48 AM, [hidden email] wrote:
>>
>>
>> I am trying to connect a KX2 (which has a standard headphone output and microphone input on separate 3.5mm jacks) to a laptop that has an integrated (4 pin TRRS) microphone input and sound output. I have the adapter than converts the 4-pin 3.5 mm jack to two separate jacks, for a microphone input (to the laptop) and sound out (from the laptop). I connected those jacks to the corresponding jacks on the KX2, using stereo cables. This is the exact configuration as shown in Frank Cady’s KX2 book.
>>
>> On transmit, everything works fine. I can key the radio from N1MM, send CW (via KY commands), and send digital data (e.g., FT8) to the radio and the radio transmits everything fine. All levels can be adjusted to perfection.
>>
>> On receive, I’ve got nada. I can’t see any audio coming from the radio into the laptop. If I disconnect the external input, I can actually decode digital data with audio from the radio’s speaker, through the air, to the laptop’s internal microphone. Now, I can deal with the differences in levels, if necessary, but I’m not getting ANY audio from the radio to the laptop via the cabling. What am I missing? I’m hoping to make this work without lots of little adapter boxes, USB hubs, external codecs, etc. for very-portable operation.
>>

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[KE1B]

> On Sep 14, 2018, at 9:57 AM, Brad Noblet <[hidden email]> wrote:
>
> Rich - For older iPhones with an 1/8” headset jack, you needed to put a 2k resistor to ground on the mic pin for the iPhone to enable audio input.  This may be true for Mac laptops mic inputs as well.  So if your KX2 has audio out with nothing connected, you might try that.  As the mic jack has DC on it to power the microphone it assumes you’re plugging in, you’ll obviously need to capacitively couple your audio source.  The 2k resistor draws the DC current to fake out the Mac into believing you plugged in a mic.  I shot 2 days trying to track this down when it happened to me.  
>

Now that I have a *working* configuration (with a simple mono cable), I may optimize it by making a cable that takes the two stereo outputs from the KX2, puts a series R-C combination on each (a few hundred ohms and a microfarad or more, to block the DC), and then ties them together to a mono plug. That should work and keep everyone (the computer and the KX2) happy.

Rich KE1B


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