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trying to make an audio loopback/antenna cable for FM recording
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Bob F
Jan 14, 2023, 2:17:51 PM1/14/23
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I have been trying to get my Galaxy S9 to record FM radio programs.
NextRadio is the only app that I have gotten to work to receive FM using
the internal tuner, but it has no record capability.
I have the app Audio Recorder loaded, which works for a headphone/w
microphone well, but does not work with the Recording Source set to
internal audio with the NextRadio app, which I had hoped would work.
So, I am trying to make a cable from a 4 wire TRRS audio cable that can
plug into the phone, acting as the FM antenna, and feed reduced signal
from the audio outputs from the phone into the microphone signal input
to the phone.
I used a 29.5 inch length of the audio cable with the TRRS male plug at
one end, and built the following circuit at the other end, hoping the
would signal the phone that it has earphones and a microphone connected
to the phone so Audio Recorder can record from the back fed headphone
output.
https://source.android.com/docs/core/audio/latency/loopback
Unfortunately, this is not working. It seems the phone is not detecting
the signal coming in as an external mic, and picks up the intern phone
mic instead. My understanding is that the phone looks for the impedance
of a mic to make the switch, and it seem the resisters in the above
circuit is not causing that to happen.
If anyone has knowledge about what the phone expects to make the mic
switch, I can definitely use some help. A record app that can force
external mic switching could be a solution. A FM radio program that can
use internal audio or that has built in record function that will work
on the S9 could also be my solution.
NextRadio is the only app that I have gotten to work to receive FM using
the internal tuner, but it has no record capability.
I have the app Audio Recorder loaded, which works for a headphone/w
microphone well, but does not work with the Recording Source set to
internal audio with the NextRadio app, which I had hoped would work.
So, I am trying to make a cable from a 4 wire TRRS audio cable that can
plug into the phone, acting as the FM antenna, and feed reduced signal
from the audio outputs from the phone into the microphone signal input
to the phone.
I used a 29.5 inch length of the audio cable with the TRRS male plug at
one end, and built the following circuit at the other end, hoping the
would signal the phone that it has earphones and a microphone connected
to the phone so Audio Recorder can record from the back fed headphone
output.
https://source.android.com/docs/core/audio/latency/loopback
Unfortunately, this is not working. It seems the phone is not detecting
the signal coming in as an external mic, and picks up the intern phone
mic instead. My understanding is that the phone looks for the impedance
of a mic to make the switch, and it seem the resisters in the above
circuit is not causing that to happen.
If anyone has knowledge about what the phone expects to make the mic
switch, I can definitely use some help. A record app that can force
external mic switching could be a solution. A FM radio program that can
use internal audio or that has built in record function that will work
on the S9 could also be my solution.
Bodger
Jan 14, 2023, 4:03:21 PM1/14/23
to
On 1/14/2023 2:17 PM, Bob F wrote:
> I have been trying to get my Galaxy S9 to record FM radio programs.
> NextRadio is the only app that I have gotten to work to receive FM using
> the internal tuner, but it has no record capability.
snip...
> I have been trying to get my Galaxy S9 to record FM radio programs.
> NextRadio is the only app that I have gotten to work to receive FM using
> the internal tuner, but it has no record capability.
I have no idea about your problem but I'm gobsmacked that a phone has an
external microphone input. I've never seen or heard of such a thing.
Bob F
Jan 14, 2023, 4:25:22 PM1/14/23
to
with headphones that include a mic with a 4 conductor TRRS plug. I think
that is pretty common.
I should add to the original post that my OS is updated to Android 10,
G960UTUES9FVD1.
Carlos E.R.
Jan 14, 2023, 4:37:57 PM1/14/23
to
same connector and cable have provision for a microphone.
--
Cheers, Carlos.
Bodger
Jan 14, 2023, 6:29:10 PM1/14/23
to
microphone input. Probably some gray cells are winking out from lack of use...
Bob F
Jan 20, 2023, 11:51:00 PM1/20/23
to
On 1/18/2023 9:15 AM, Charles Lucas wrote:
> A signal always travels from its output to its input as long as the rules of proper
> power and impedance are followed along the way- kind of like a glorified postal
> system, from a conceptual sense.
>
> The headphone jack can be use as a variable audio output jack when using a patch
> cord or Y-adapter patch cable from that device to an RCA audio R/L audio input on
> an analog recording device (converting the impedance from an 1/8" (3.5 mm) jack
> at 32 ohms to an RCA jack at 1000 ohms) which leads up to an analog device.
>
> Or you can use an 1/8" male to male patch cable to go to a computer line input or
> other similar device to convert the signal to a digital sampler (starting out as analog
> and then getting converted to a digital media in the processing). You have to remember
> level control is also very important. Don't overload the headphone outs with "too much"
> signal (or distortive audio) or avoid overdriving the signal.
>
I tried a half dozen recording apps to try to record the NextRadio audio
from the headphone jack back at a lower level into the mic input. One of
them "Voice recorder" 21.3.55.16, causes NextRadio to stop
receiving/outputting the FM audio while it is recording.
The other recording apps I tried would let NextRadio keep going, but the
app shows zero signal, so no audio gets recorded.
I tried a couple of the apps while playing an mp3 file on the phone, and
the audio was recorded properly.
So, it really seems like NextRadio is doing something wierd to prevent
recording of it's output.
Can anyone propose what they might be doing, or ways to get past it.
I cannot find any other FM apps that will run on my S9.
> power and impedance are followed along the way- kind of like a glorified postal
> system, from a conceptual sense.
>
> The headphone jack can be use as a variable audio output jack when using a patch
> cord or Y-adapter patch cable from that device to an RCA audio R/L audio input on
> an analog recording device (converting the impedance from an 1/8" (3.5 mm) jack
> at 32 ohms to an RCA jack at 1000 ohms) which leads up to an analog device.
>
> Or you can use an 1/8" male to male patch cable to go to a computer line input or
> other similar device to convert the signal to a digital sampler (starting out as analog
> and then getting converted to a digital media in the processing). You have to remember
> level control is also very important. Don't overload the headphone outs with "too much"
> signal (or distortive audio) or avoid overdriving the signal.
>
I tried a half dozen recording apps to try to record the NextRadio audio
from the headphone jack back at a lower level into the mic input. One of
them "Voice recorder" 21.3.55.16, causes NextRadio to stop
receiving/outputting the FM audio while it is recording.
The other recording apps I tried would let NextRadio keep going, but the
app shows zero signal, so no audio gets recorded.
I tried a couple of the apps while playing an mp3 file on the phone, and
the audio was recorded properly.
So, it really seems like NextRadio is doing something wierd to prevent
recording of it's output.
Can anyone propose what they might be doing, or ways to get past it.
I cannot find any other FM apps that will run on my S9.
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