Replacing Electret Microphone With Audio Input?

On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--
Click to expand...
iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.
 
On Feb 15, 1:28 pm, et...@FreeNet.Carleton.CA (Michael Black) wrote:
"Dave.H" (the19...@googlemail.com) writes:
On Feb 15, 10:45 am, "Dave.H" <the19...@googlemail.com> wrote:
I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

I found a circuit that does use a regular audio input, but I can't
find a couple of capacitor values at Dick Smith. The caps have to be
ceramic. I can find a 3.3 pF for the 3 pF, but I can't find a 10 nF
ceramic unit. Would it be OK to just parallel 10 1 nF caps, until I
can find a 10 nF unit?

10nF is .01.

1nF= .001
10nF=.01

Thus you need the extremely common .01uF capacitor. And I suspect
that's not even critical, such a large value is bound to be a bypass
capacitor and hence something around that value will do fine.

Michael
Click to expand...
I somehow managed to read the chart wrong @ http://www.justradios.com/uFnFpF.html
Handy chart to have by the way.
 
On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.
Click to expand...
You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--
 
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--
Click to expand...
No, the one @ http://www.techlib.com/Karen/radio.htm#FM%20Transmitter
 
On Fri, 15 Feb 2008 04:56:18 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

On Feb 15, 2:18 pm, "Dave.H" <the19...@googlemail.com> wrote:
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:



On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--

No, the one @http://www.techlib.com/Karen/radio.htm#FM%20Transmitter

The article linked to previously mentioned using a 5-20 pF trimmer cap
instead of a fixed capacitor. What capacitor do I need to replace to
install a 4.2pF-20pF trimmer? This would make it easier to tune.
Click to expand...
The 12 pf cap is the tank circuit tuning cap; spreading or
compressing the coil will also tune it.

The 3 pf is a feedback cap and gets it oscillating. The .01 is a
bypass cap and not critical to anything. The 1 nf on the base is a
bypass but will affect audio frequency's as well.
--
 
On Fri, 15 Feb 2008 05:21:19 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

On Feb 16, 12:16 am, default <defa...@defaulter.net> wrote:
On Fri, 15 Feb 2008 04:56:18 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:
On Feb 15, 2:18 pm, "Dave.H" <the19...@googlemail.com> wrote:
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:

On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--

No, the one @http://www.techlib.com/Karen/radio.htm#FM%20Transmitter

The article linked to previously mentioned using a 5-20 pF trimmer cap
instead of a fixed capacitor. What capacitor do I need to replace to
install a 4.2pF-20pF trimmer? This would make it easier to tune.

The 12 pf cap is the tank circuit tuning cap; spreading or
compressing the coil will also tune it.

The 3 pf is a feedback cap and gets it oscillating. The .01 is a
bypass cap and not critical to anything. The 1 nf on the base is a
bypass but will affect audio frequency's as well.
--

So if I got this right, I replace the 12 pF?
Click to expand...
Yes, put a variable in place of it. The plate of the variable that
the adjustment screwdriver touches should be the ground side so the
adjustment tool doesn't cause it to change freq..

Just look at the cap to determine which side should be ground, It is
normally obvious.
--
 
On Feb 15, 2:18 pm, "Dave.H" <the19...@googlemail.com> wrote:
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:



On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--

No, the one @http://www.techlib.com/Karen/radio.htm#FM%20Transmitter
Click to expand...
The article linked to previously mentioned using a 5-20 pF trimmer cap
instead of a fixed capacitor. What capacitor do I need to replace to
install a 4.2pF-20pF trimmer? This would make it easier to tune.
 
On Feb 16, 12:16 am, default <defa...@defaulter.net> wrote:
On Fri, 15 Feb 2008 04:56:18 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:
On Feb 15, 2:18 pm, "Dave.H" <the19...@googlemail.com> wrote:
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:

On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--

No, the one @http://www.techlib.com/Karen/radio.htm#FM%20Transmitter

The article linked to previously mentioned using a 5-20 pF trimmer cap
instead of a fixed capacitor. What capacitor do I need to replace to
install a 4.2pF-20pF trimmer? This would make it easier to tune.

The 12 pf cap is the tank circuit tuning cap; spreading or
compressing the coil will also tune it.

The 3 pf is a feedback cap and gets it oscillating. The .01 is a
bypass cap and not critical to anything. The 1 nf on the base is a
bypass but will affect audio frequency's as well.
--
Click to expand...
So if I got this right, I replace the 12 pF?
 
On Feb 16, 12:27 am, default <defa...@defaulter.net> wrote:
On Fri, 15 Feb 2008 05:21:19 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:
On Feb 16, 12:16 am, default <defa...@defaulter.net> wrote:
On Fri, 15 Feb 2008 04:56:18 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 2:18 pm, "Dave.H" <the19...@googlemail.com> wrote:
On Feb 15, 1:52 pm, default <defa...@defaulter.net> wrote:

On Thu, 14 Feb 2008 18:38:55 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
On Feb 15, 1:20 pm, default <defa...@defaulter.net> wrote:
On Thu, 14 Feb 2008 18:15:00 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

default wrote:
On Thu, 14 Feb 2008 15:45:31 -0800 (PST), "Dave.H"
the19...@googlemail.com> wrote:

I am looking at a number of FM transmitter circuits, purely as a
project, but all of them use electret microphones as input. Would it
be possible to replace this with an audio input for my iPod?

Of course. You wouldn't have stereo with a simple one or two
transistor transmitter - so you may also want to combine both channels
going in.
\

I understand that, but my radio receiver is a mono type anyway, so I'm
not looking for a stereo version.
--

sorry I somehow got the idea that the Ipod would be the music source.
--

iPod is the music source, it will be broadcasting to the mono radio. I
will use that circuit I linked to before, seems to have the audio
channels combined by 10K resistors so I don't have to worry about
that. Even though I've already got a device that combines left and
right with 1.8K resistors.

You have a better idea of what you are doing than I do. The Ipod
output has to (should) be mixed to drive the transmitter with the
contents of both channels. That can be as simple as two resistors
from each channel to a common input.

Not aware of the circuit you linked to before. You aren't referring
to the one where you ground the two signals to control volume are you?
--

No, the one @http://www.techlib.com/Karen/radio.htm#FM%20Transmitter

The article linked to previously mentioned using a 5-20 pF trimmer cap
instead of a fixed capacitor. What capacitor do I need to replace to
install a 4.2pF-20pF trimmer? This would make it easier to tune.

The 12 pf cap is the tank circuit tuning cap; spreading or
compressing the coil will also tune it.

The 3 pf is a feedback cap and gets it oscillating. The .01 is a
bypass cap and not critical to anything. The 1 nf on the base is a
bypass but will affect audio frequency's as well.
--

So if I got this right, I replace the 12 pF?

Yes, put a variable in place of it. The plate of the variable that
the adjustment screwdriver touches should be the ground side so the
adjustment tool doesn't cause it to change freq..

Just look at the cap to determine which side should be ground, It is
normally obvious.
--
Click to expand...
Thanks, I don't really like the idea of fiddling with the coil, I like
to leave coils alone. The trimmer I'm going to use is a PCB mount
one, from Dick Smith of course Cat # R2945
 
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