sound card AM Transmitter

Jerry Avins wrote:
> 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.

Just a brief google, but at least this card goes to 45kHz so maybe 
higher isn't out of the question
http://www.music.columbia.edu/pipermail/music-dsp/2002-November/051645.html

-- 
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

On Jul 30, 8:30 pm, "Masood" <m_abbasi9...@yahoo.com> 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.

You could make a crude Audio AM transmitter and receiver using 2 pcs
using say a 10kHz carrier. Not very practical of course but would be
interesting. You may even be able to narrowband FM it too. You could
send a sine wave of say 4kHz on top of the 10kHz acoustic carrier.
Very crude..To do this with e/m...work out what a 10kHz wavelength is
and divide by 4. I make it 7.5km! Use a nearby mountain range for
this! Then you can speak to submarines.

K.

On Jul 30, 8:30 pm, "Masood" <m_abbasi9...@yahoo.com> 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.

http://www.vlf.it/

Read some of this.

Dirk Bruere at NeoPax wrote:
> Jerry Avins wrote:
>> 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.
> 
> Just a brief google, but at least this card goes to 45kHz so maybe 
> higher isn't out of the question
> http://www.music.columbia.edu/pipermail/music-dsp/2002-November/051645.html

This is Masood's first sentence in opening this thread: "I want to 
transmit AM RF signal (1khz to 20 KHz) using sound card."

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

Jerry Avins wrote:
> Dirk Bruere at NeoPax wrote:
>> Jerry Avins wrote:
>>> 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.
>>
>> Just a brief google, but at least this card goes to 45kHz so maybe 
>> higher isn't out of the question
>> http://www.music.columbia.edu/pipermail/music-dsp/2002-November/051645.html 
>>
> 
> This is Masood's first sentence in opening this thread: "I want to 
> transmit AM RF signal (1khz to 20 KHz) using sound card."

Perhaps he needs to tell us what he hopes to achieve, rather than ask 
for a specific implementation.

-- 
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:
>>>> 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.
>>>
>>> Just a brief google, but at least this card goes to 45kHz so maybe 
>>> higher isn't out of the question
>>> http://www.music.columbia.edu/pipermail/music-dsp/2002-November/051645.html 
>>>
>>
>> This is Masood's first sentence in opening this thread: "I want to 
>> transmit AM RF signal (1khz to 20 KHz) using sound card."
> 
> Perhaps he needs to tell us what he hopes to achieve, rather than ask 
> for a specific implementation.

Indeed! Keep trying.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

I know that people here are expert in dsp so my questions might feel to
all of you stupid. I came to know from internet that sound card could be
used to produce sine wave within limits(due to sampling rate) and therfore
1-20 khz could be produced easily. if it's true then it means we can also
change the amplitude of the wave to produce an AM signal coresponding to
the voice and frequency will be fixed, for digital data it would become
ASK. the issue is not to transmit to several miles but to inches as the
other computer will be several inches or approx half meter away, in my
first post i wrote that i have developed SDR pc based. one PC i want to
Transmit AM signal through sound card directly connected to antenna(range
of half meter is required) and other computer sound card to receive, the
other computer has preamplifier before feed to sound card where my sdr
will be running.

i think issue that developed here is due to the requirement i raised for
the production of AM. if still it's unclear then i want jerry to send me
schemtics of AM transmitter he has built so that i can check my SDR by
receiving the low frequency AM transmission, i am using active antenna
front end ionce built and succesfully received AM transmissions.

Thanks to All again

Masood wrote:
> I know that people here are expert in dsp so my questions might feel to
> all of you stupid. I came to know from internet that sound card could be
> used to produce sine wave within limits(due to sampling rate) and therfore
> 1-20 khz could be produced easily. if it's true then it means we can also
> change the amplitude of the wave to produce an AM signal coresponding to
> the voice and frequency will be fixed, for digital data it would become
> ASK. the issue is not to transmit to several miles but to inches as the
> other computer will be several inches or approx half meter away, in my
> first post i wrote that i have developed SDR pc based. one PC i want to
> Transmit AM signal through sound card directly connected to antenna(range
> of half meter is required) and other computer sound card to receive, the
> other computer has preamplifier before feed to sound card where my sdr
> will be running.
> 
> i think issue that developed here is due to the requirement i raised for
> the production of AM. if still it's unclear then i want jerry to send me
> schemtics of AM transmitter he has built so that i can check my SDR by
> receiving the low frequency AM transmission, i am using active antenna
> front end ionce built and succesfully received AM transmissions.
> 
> Thanks to All again

http://en.wikipedia.org/wiki/Induction_loop

-- 
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:
> I know that people here are expert in dsp so my questions might feel to
> all of you stupid. I came to know from internet that sound card could be
> used to produce sine wave within limits(due to sampling rate) and therfore
> 1-20 khz could be produced easily. if it's true then it means we can also
> change the amplitude of the wave to produce an AM signal coresponding to
> the voice and frequency will be fixed, for digital data it would become
> ASK. the issue is not to transmit to several miles but to inches as the
> other computer will be several inches or approx half meter away, in my
> first post i wrote that i have developed SDR pc based. one PC i want to
> Transmit AM signal through sound card directly connected to antenna(range
> of half meter is required) and other computer sound card to receive, the
> other computer has preamplifier before feed to sound card where my sdr
> will be running.
> 
> i think issue that developed here is due to the requirement i raised for
> the production of AM. if still it's unclear then i want jerry to send me
> schemtics of AM transmitter he has built so that i can check my SDR by
> receiving the low frequency AM transmission, i am using active antenna
> front end ionce built and succesfully received AM transmissions.
> 
> Thanks to All again

In order to understand what you can and can't achieve, you need to 
understand the nature of an AM signal. It consists of a carrier 
surrounded by upper and lower sidebands that result from the modulation. 
The upper sideband is a frequency-shifted replica of the modulating 
signal, while the lower sideband is it's reflection about the carrier 
frequency. The whole signal occupies a band of frequencies twice as wide 
as the modulating signal, centered about the carrier frequency. There 
must be no distortion of the phases of the signal components.

Telephone-quality speech occupies a band of frequencies no more than 
four KHz; three is enough for reasonable intelligibility. Since the 
upper limit of the upper sideband must fit within the capability of the 
sound card, and few cards can produce signals above 20 KHz, the carrier 
itself can be no higher than 16 or 17 KHz. A guard band will help to 
avoid phase distortion. A sound card can produce the waveform you want. 
The general equation of an AM signal is w_c*(1+x_m), where w_c (or 
2*pi*f_c)is the carrier frequency and x_m is the modulating signal. 
There are many ways to produce the samples for w_c and the x_m are the 
samples of the modulating signal.

For transmission of only a few feet, why not send the unmodulated signal 
down a wire? An infra-red link is more appropriate if wireless operation 
is a firm requirement.

My crystal transmitter would be useless for you. It was a pair of 
circuits tuned to 770 and 1540 KHz driving a full-wave bridge to 
generate a strong second harmonic. The bridge output returned through a 
carbon microphone, and so modulated the harmonic. (I worked in the 
shadow of the WJZ (770 KHz; now WABC) antenna tower, and the signal was 
strong enough to drive a loudspeaker from an unamplified crystal 
receiver with a loop antenna. Rotating the antenna controlled the 
volume.) The crystal transmitter served as an intercom with a receiver 
in the office tuned to 1540 KHz serving as the other end. WQXR at 1560 
didn't interfere.

Good luck!

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������