Forums

sound card AM Transmitter

Started by Masood July 30, 2008
Jerry Avins wrote:
> 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
Maybe it's not an antenna in the RF sense but an inductive loop device. -- 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
Dirk Bruere at NeoPax wrote:
> Jerry Avins wrote: >> 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 > > Maybe it's not an antenna in the RF sense but an inductive loop device.
So why modulate? We've seen Masoud's questions before. Some of them make sense, but none admit the kinds of sophistication that others are willing to suppose. 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;
Jerry Avins wrote:
> Dirk Bruere at NeoPax wrote: >> Jerry Avins wrote: >>> 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 >> >> Maybe it's not an antenna in the RF sense but an inductive loop device. > > So why modulate? We've seen Masoud's questions before. Some of them make > sense, but none admit the kinds of sophistication that others are > willing to suppose.
IIRC inductive loop stuff is modulated carrier at around 100kHz Bandwidth limiting the signal to a few kHz and modulating a 20kHz carrier should be good enough for voice. -- 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
Dirk Bruere at NeoPax wrote:
> Jerry Avins wrote: >> Dirk Bruere at NeoPax wrote: >>> Jerry Avins wrote: >>>> 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 >>> >>> Maybe it's not an antenna in the RF sense but an inductive loop device. >> >> So why modulate? We've seen Masoud's questions before. Some of them >> make sense, but none admit the kinds of sophistication that others are >> willing to suppose. > > IIRC inductive loop stuff is modulated carrier at around 100kHz > Bandwidth limiting the signal to a few kHz and modulating a 20kHz > carrier should be good enough for voice.
Do you know any sound cards that can reproduce 100 KHz with sidebands? Masoud doesn't know better, but you ought to. 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, 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. >??????????????????????????????????????????????????????????????????????? >
I thank all for the reply, I should have clearly mention the requirement, actually i have devloped software radio for AM demodulation using sound card and using other computer i want to generate required signal so computer sound card to sound card connection will be made not necessarily a Radio connection for 0-4 khz modulating signal
Masood wrote:
>> 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. >> ??????????????????????????????????????????????????????????????????????? >> > > > I thank all for the reply, I should have clearly mention the requirement, > actually i have devloped software radio for AM demodulation using sound > card and using other computer i want to generate required signal so > computer sound card to sound card connection will be made not necessarily > a Radio connection for 0-4 khz modulating signal
What is the carrier frequency of the signal you demodulate with the help of your sound card? If you describe clearly how your receiver works, perhaps we can modify it to produce the signal you want. Crystal receivers were popular hobby projects when I was a kid. They required no power supply other than the receiving antenna. I once built a crystal transmitter that also required no power. Its range was a few hundred feet. Jerry -- Engineering is the art of making what you want from things you can get.
Jerry Avins wrote:
(snip)

> Do you know any sound cards that can reproduce 100 KHz with sidebands? > Masoud doesn't know better, but you ought to.
I thought he wanted 20kHz. NIST used to believe that 20kHz was a fine carrier frequency, but last I knew the time standard had moved up to 60kHz. There are also stories of submarine radio transmitters at 7Hz. (The resonant frequency of the earth for radio signals.) -- glen
ypg wrote:
(snip)

> 1)At 20Khz carrier freq (say) , wavelength will be of the order of 15Km , > antenna of that order is not feasible.
For low frequencies you use inductive, or loop, antennae. I remember a design from some years ago for a 20kHz receiving antenna for the WWV digital time signal, as a shielded loop antenna. A piece of electrical conduit is bent into a loop, connected to a junction box with one side using an insulated (plastic) coupling. Maybe 10 turns of wire through the conduit, and an amplifier in the junction box. The conduit will shield out much electrical interference that would otherwise saturate the amplifier, coupling to the magnetic part of the EM wave. (That explanation might not be exactly right, but I don't think it is too far off.) -- glen
glen herrmannsfeldt wrote:
> Jerry Avins wrote: > (snip) > >> Do you know any sound cards that can reproduce 100 KHz with sidebands? >> Masoud doesn't know better, but you ought to. > > I thought he wanted 20kHz. NIST used to believe that 20kHz > was a fine carrier frequency, but last I knew the time > standard had moved up to 60kHz. > > There are also stories of submarine radio transmitters at 7Hz. > (The resonant frequency of the earth for radio signals.)
Glen, Have you been following the thread? Masood wants to make an AM transmitter using a sound card. The length of the necessary antenna became an issue. Dirk of NeoPax suggested that an inductive loop at 100 KHz might be intended; I responded to that. Masood has at last responded with some details. I asked for more. Maybe it will soon become clearer. 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, 10:59 pm, "Masood" <m_abbasi9...@yahoo.com> wrote:

> I thank all for the reply, I should have clearly mention the requirement, > actually i have devloped software radio for AM demodulation using sound > card and using other computer i want to generate required signal so > computer sound card to sound card connection will be made not necessarily > a Radio connection for 0-4 khz modulating signal
If your receiver uses a single channel of the soundcard, then you need to synthesize a sine wave of the desired carrier frequency, multiply it by your modulation scaling the amplitude appropriately, and send to the transmitter sound card. If your receiver takes I & Q inputs by using both channels of a stereo sound card, you will need to synthesize both a sine and a cosine, multiply each by the same modulating signal, and send one out each channel of the sound card. You may have some problems with the IQ approach as the soundcard audio jacks may have DC blocking capacitors giving you a hole in the spectrum near zero hz.