Android Audio Output/Tx Problem

[VK1TRL]

Hi folks,

I'm hoping this is a problem that others have encountered and have a solution for:

I'm trying to use FT8CN on an Android mobile phone. I have also made an adapter cable that uses the headphone jack on the phone and splits it into Audio Out and Audio In.

On the Android -> trusdx side, I have disconnected the tip, joined the left and right audio outputs (from the Android) onto the ring, and have ground on the sleeve.
On the trusdx -> Android side, it is unchanged microphone input to the Android, connected to the output of the trusdx.

With this setup, I am able to receive and decode without issues. The problem I am having is with transmitting.
When the (Android) Audio Output is disconnected from the trusdx, the Android recognises that there is a headphone jack inserted and tries to output audio through the disconnected line.
When the (Android) Audio Output is connected to the trusdx Mic input, the Android thinks that the headphone is not connected and will try to output audio through the (Android's) speaker. The built-in microphone on the trusdx also seems to be able to hear the audio from the Android, because I appear to be able to have a QSO over FT8 with audio provided via the Android's Speaker -> trudsx microphone (though I may be misinterpreting how a QSO in the app works).

I have double checked my adapter cable - no shorts to ground, and connected correctly, as far as I can tell, but I'm still at a loss as to where the issue lies.

Thanks,

VK1TRL

[Cthulhu]

I used a set like this from standard cables and an adapter. One cable needs to be modified by disconnecting the centre strand. With this cable I already have a lot of QSO in FT8 , the furthest is about 10000 kilometres. In WSPR I have heard stations over 18000 km. Also received SSTV
PS Honor 8x + FT8CN + Loud Band (WSPR) + Robot36 (SSTV)

Android-ft8.jpg (226.89 KiB) Viewed 580 times

[VK1TRL]

Thank you,

I tried connecting only ground and one speaker wire today, both for the left audio output and the right.

In one configuration, the Android device did not recognise that the headphone lead was connected, in the other, it was recognised but I could not be heard.

Where should I be looking next?

[vk2eta@gmail.com]

The Android devices detect the plugging in of the jack by the load they see on the speakers and microphone connections.

Try a 10 ohms resistor to ground on each audio output channels to make the device believe it has a headphone plugged in.

For the mic side it needs to see 1k ohms to 2k ohms (seems device dependant).

As a starting point see page 25 of the AndFlmsg manual:

https://bitbucket.org/VK2ETA/andflmsg/d ... -1.6.0.pdf

73, John (VK2ETA)

[Luca66]

I use a dongle like this, with modification of the cable that enters the mic of the tr usdx. https://images.app.goo.gl/UnhKUjnoUudpvq457
I have a Samsung A3.
73