FM stereo transmitter?

[Bob Masta]

Here's the scenario: I'd like to be able to
play an audiobook on my living room stereo
where my wife would be listening as she
works on her projects, but I want to be able
to listen at the same time on a Walkman
while I'm working in the basement, etc.
Rather than string wires, this seems like a
perfect application for a little FM transmitter.

But when I Google for such a beast, I am
overwhelmed by the number of products,
from under $20 to over $200.

It looks like many of the cheaper products
are intended just to get sound from some
portable device into a car radio, so I would
guess that the range may be intentionally
limited. Or can I just run a long antenna
on the transmitter?

Anyone have any experience with such
devices?

Best regards,





Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[MRW]

Bob Masta wrote:

Or can I just run a long antenna
on the transmitter?

I suppose you can, but you have to worry about matching the antenna
with the transmitter output to ensure that you minimize the reflection
coefficient. From my experience, the output has an impedance of 50
ohms. Running a simple dipole antenna at about half or a quarter of a
wavelength of the FM frequency can probably work, but some FM
transmitters have a fold-back scheme. This means that if you don't have
proper matching (high VSWR - voltage standing wave ratio), then the
output power is cut back (folded back) to minimize the reflected power
to the transmitter.

Anyone have any experience with such
devices?

My friend had an iPod FM transmitter that was able to interfere with
cars on the next lane. I guess he tweaked its power output. I wouldn't
be surprised that most of the cheapo FM transmitter (iPod included)
uses Maxim's MAX2605-2609 FM IC. You can request samples from Maxim and
try building your own. The datasheet includes a basic FM application. I
think with this one you can get away with running a long wire as your
antenna and still receive decent field strength in your basement.

 

[MRW]

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

By the way, thanks for DaqGen. I'm using it as my signal generator for
my audio experiments.

 

[Charles Schuler]

Here's the scenario: I'd like to be able to
play an audiobook on my living room stereo
where my wife would be listening as she
works on her projects, but I want to be able
to listen at the same time on a Walkman
while I'm working in the basement, etc.
Rather than string wires, this seems like a
perfect application for a little FM transmitter.

But when I Google for such a beast, I am
overwhelmed by the number of products,
from under $20 to over $200.

Beware of the ones with LC oscillators as they drift like crazy and are
junk.

 

[Joerg]

Here's the scenario: I'd like to be able to
play an audiobook on my living room stereo
where my wife would be listening as she
works on her projects, but I want to be able
to listen at the same time on a Walkman
while I'm working in the basement, etc.
Rather than string wires, this seems like a
perfect application for a little FM transmitter.

But when I Google for such a beast, I am
overwhelmed by the number of products,
from under $20 to over $200.

It looks like many of the cheaper products
are intended just to get sound from some
portable device into a car radio, so I would
guess that the range may be intentionally
limited. Or can I just run a long antenna
on the transmitter?

Anyone have any experience with such
devices?

It's usually not intentionally limited but the FCC limits what they can
do. If the basement is almost underneath the living room and you don't
have concrete floors above like we do it might work. A month ago I saw a
modulator for $19.95 at Target. Thing is, these are limited to four
frequencies at the low end of the FM band. So first you have to make
sure that at least one of them isn't occupied by a strong station.

 

[Rich Webb]

Here's the scenario: I'd like to be able to
play an audiobook on my living room stereo
where my wife would be listening as she
works on her projects, but I want to be able
to listen at the same time on a Walkman
while I'm working in the basement, etc.
Rather than string wires, this seems like a
perfect application for a little FM transmitter.

But when I Google for such a beast, I am
overwhelmed by the number of products,
from under $20 to over $200.

It looks like many of the cheaper products
are intended just to get sound from some
portable device into a car radio, so I would
guess that the range may be intentionally
limited. Or can I just run a long antenna
on the transmitter?

Anyone have any experience with such
devices?

Ramsey is the go-to place for these small FM transmitters. Most
available as kits, some also as assembled.

http://www.ramseyelectronics.com/hk/default.asp?page=amfm

 

[Bob Masta]

By the way, thanks for DaqGen. I'm using it as my signal generator for
my audio experiments.

You are most welcome! As it turns out, I am
putting the finishing touches on Daqarta for Windows.
(Probably a couple more weeks until release.)
I won't be developing DaqGen any more as a stand-alone
app, since Daqarta includes all DaqGen's features
plus a whole lot more. But even though Daqarta is
shareware (not freeware), you will still be able to use
it as a freeware generator since when the trial period
expires all that happens is it no longer allows you to
see inputs from the outside world... which DaqGen
can't do anyway. You will be left with all the DaqGen
features, plus all the new features from Daqarta
(except inputs)... for free!

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[Eric R Snow]

Ramsey is the go-to place for these small FM transmitters. Most
available as kits, some also as assembled.

http://www.ramseyelectronics.com/hk/default.asp?page=amfm

I have one of their FM kits. It's the one that is digitally tuned,
about $100.00 I think. It works very well, no drift at all. The sound
quality is great.
ERS