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sound card AM Transmitter

Started by Masood July 30, 2008
Hi All,

I want to transmit AM RF signal (1khz to 20 Khz) using sound card.
The audio out of sound card will be connected to Antenna directly.
i need software that take sound file and generate AM RF signal
for the above range and produce desired AM signal to be transmited on
air,
high out put power is not required,
I am unable to find any software, Any help by anyone will be highly
appreciated. thanks in advace.
Masood wrote:
> Hi All, > > I want to transmit AM RF signal (1khz to 20 Khz) using sound card. > The audio out of sound card will be connected to Antenna directly. > i need software that take sound file and generate AM RF signal > for the above range and produce desired AM signal to be transmited on > air, > high out put power is not required, > I am unable to find any software, Any help by anyone will be highly > appreciated. thanks in advace.
And how big will your antenna be? -- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
Masood wrote:
> Hi All, > > I want to transmit AM RF signal (1khz to 20 Khz) using sound card. > The audio out of sound card will be connected to Antenna directly. > i need software that take sound file and generate AM RF signal > for the above range and produce desired AM signal to be transmited on > air, > high out put power is not required, > I am unable to find any software, Any help by anyone will be highly > appreciated. thanks in advace.
What receiver do you plan to use ?? The receiver will have an RF front end, so the "transmitter" _must_ have an RF back end. This _cannot_ be done in software from a sound card. donald
> >Hi All, > >I want to transmit AM RF signal (1khz to 20 Khz) using sound card. >The audio out of sound card will be connected to Antenna directly. >i need software that take sound file and generate AM RF signal >for the above range and produce desired AM signal to be transmited on >air, >high out put power is not required, >I am unable to find any software, Any help by anyone will be highly >appreciated. thanks in advace. >
As dirk has rightfully pointed out , the antenna required will be impractically long . 1)At 20Khz carrier freq (say) , wavelength will be of the order of 15Km , antenna of that order is not feasible. 2) Music may have freq like 15Khz , u cannot amplitude modulate 15Khz signal with a carrier of 20Khz. Carrier should be of a comparatively high freq as compared to the signal being modulated. Regards Yogesh PG

Masood wrote:

> Hi All, > > I want to transmit AM RF signal (1khz to 20 Khz) using sound card. > The audio out of sound card will be connected to Antenna directly. > i need software that take sound file and generate AM RF signal > for the above range and produce desired AM signal to be transmited on > air, > high out put power is not required, > I am unable to find any software, Any help by anyone will be highly > appreciated. thanks in advace.
How big is the high appreciation? Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On Jul 30, 9:31 am, "ypg" <yogesh_ghar...@yahoo.com> wrote:

> 1)At 20Khz carrier freq (say) , wavelength will be of the order of 15Km , > antenna of that order is not feasible.
Unlicensed hobbyist VLF transmitters are legally limited to antennas of short dimension that are a small fraction of a wavelength. They aren't intended to be good antennas !
> 2) Music may have freq like 15Khz , u cannot amplitude modulate 15Khz > signal with a carrier of 20Khz. Carrier should be of a comparatively high > freq as compared to the signal being modulated.
A common misconception. You can quite successfully modulate a carrier of zero frequency if you feel like it, though you will need a signal path that is good down to DC. Needless to say it won't propagate very well between antennas. If your bandwidth of interest crosses through zero Hz and is not symmetric, then you will probably need separate quadrature signals (I & Q) to be able to tell positive and negative frequencies apart. But if your carrier is say 10 Khz and your total bandwidth 15 Khz centered there, then your frequencies of interest are from 2.5 Khz to 17.5 Khz and a single phase will suffice. This is actually how a lot of PC-based software radio work started out - mix the RF frequency down to a carrier within the range of the soundcard's bandwidth. And note that telephone quality double sideband AM voice has a modulated bandwidth of 6-7 KHz. To answer the original poster's question: synthesize a sine wave of the desired carrier frequency and multiply it by the signal you wish to modulate it with. Send the resulting data to the sound card.
Masood wrote:
> Hi All, > > I want to transmit AM RF signal (1khz to 20 Khz) using sound card. > The audio out of sound card will be connected to Antenna directly. > i need software that take sound file and generate AM RF signal > for the above range and produce desired AM signal to be transmited on > air, > high out put power is not required, > I am unable to find any software, Any help by anyone will be highly > appreciated. thanks in advace.
"AM" stands for "amplitude modulation". Your sound card can produce the modulating signal, but not the carrier. The carrier is the signal that is modulated. You wrote nonsense that shows a lack of understanding what modulation is. Read a little more. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
cs_posting@hotmail.com wrote:
> On Jul 30, 9:31 am, "ypg" <yogesh_ghar...@yahoo.com> wrote: > >> 1)At 20Khz carrier freq (say) , wavelength will be of the order of 15Km , >> antenna of that order is not feasible. > > Unlicensed hobbyist VLF transmitters are legally limited to antennas > of short dimension that are a small fraction of a wavelength. They > aren't intended to be good antennas ! > >> 2) Music may have freq like 15Khz , u cannot amplitude modulate 15Khz >> signal with a carrier of 20Khz. Carrier should be of a comparatively high >> freq as compared to the signal being modulated. > > A common misconception. You can quite successfully modulate a carrier > of zero frequency if you feel like it, though you will need a signal > path that is good down to DC. Needless to say it won't propagate very > well between antennas. If your bandwidth of interest crosses through > zero Hz and is not symmetric, then you will probably need separate > quadrature signals (I & Q) to be able to tell positive and negative > frequencies apart. But if your carrier is say 10 Khz and your total > bandwidth 15 Khz centered there, then your frequencies of interest are > from 2.5 Khz to 17.5 Khz and a single phase will suffice. This is > actually how a lot of PC-based software radio work started out - mix > the RF frequency down to a carrier within the range of the soundcard's > bandwidth. And note that telephone quality double sideband AM voice > has a modulated bandwidth of 6-7 KHz. > > To answer the original poster's question: synthesize a sine wave of > the desired carrier frequency and multiply it by the signal you wish > to modulate it with. Send the resulting data to the sound card.
How far do you expect it to propagate with an antenna of reasonable (say 50 meter) size? What will serve as a receiver? Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
On Jul 30, 11:20 am, Jerry Avins <j...@ieee.org> wrote:

> How far do you expect it to propagate with an antenna of reasonable (say > 50 meter) size? What will serve as a receiver?
I don't expect it to propagate very far, but who knows what the OP is up to. We don't even know for a fact that antenna are involved - there could be a transmission line between transmitter and receiver. Or we could be misinterpreting the question - 20 KHz might be the modulation bandwidth, not the carrier frequency. For antenna lenght, the legal limit in the US for the 160 - 190 Khz band appears to be 15 meters for the total length of of antenna, feed line, and ground lead. I'm not sure what, if anything, is allowed below 20 KHz. If the transmitter is a sound card, the receiver might be as well. Or something involving an op-amp for gain, a diode detector, and an op- amp lowpass filter.
cs_posting@hotmail.com wrote:
> On Jul 30, 11:20 am, Jerry Avins <j...@ieee.org> wrote: > >> How far do you expect it to propagate with an antenna of reasonable (say >> 50 meter) size? What will serve as a receiver? > > I don't expect it to propagate very far, but who knows what the OP is > up to. We don't even know for a fact that antenna are involved - > there could be a transmission line between transmitter and receiver. > Or we could be misinterpreting the question - 20 KHz might be the > modulation bandwidth, not the carrier frequency. > > For antenna lenght, the legal limit in the US for the 160 - 190 Khz > band appears to be 15 meters for the total length of of antenna, feed > line, and ground lead. I'm not sure what, if anything, is allowed > below 20 KHz. > > If the transmitter is a sound card, the receiver might be as well. Or > something involving an op-amp for gain, a diode detector, and an op- > amp lowpass filter.
Be advised that the whole project is a fantasy. If a transmission line is involved, why modulate? Our friend Masood needs to learn a lot even to understand his own question. If he asks more questions, I and others will try our best to enlighten him. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;