transmitter question - its a dousy
 

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel. The big question is why you would want to
do it.
--
17 days!


Michael A. Terrell
Central Florida

duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel. The big question is why you would want to
do it.
--
17 days!


Michael A. Terrell
Central Florida

Michael A. Terrell wrote:
duckman wrote:
Is there available, can it be done to have an AM and/ and or FM
transmitter that will broadcast over the entire AM and FM broadcast band
at the same time. Or at least multiple stations. E.G.
Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel

Nah, given a wideband signal source and amplifier, there's conceptually no
reason he couldn't broadcast on all stations simultaneously! I find it a
novel idea, actually.

The big question is why you would want to
do it.

I suspect he's thinking of something like those 'talking houses' where
you're supposed to tune your radio to a given station and get information on
why you want to drop a quarter million bucks on a thousand square feet of
your very own sometime in the next 20 minutes... except he doesn't want
people to have to tune at all!

Slightly less evil would be emergency broadcasting type uses...

---Joel Kolstad

Michael A. Terrell wrote:
duckman wrote:
Is there available, can it be done to have an AM and/ and or FM
transmitter that will broadcast over the entire AM and FM broadcast band
at the same time. Or at least multiple stations. E.G.
Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel

Nah, given a wideband signal source and amplifier, there's conceptually no
reason he couldn't broadcast on all stations simultaneously! I find it a
novel idea, actually.

The big question is why you would want to
do it.

I suspect he's thinking of something like those 'talking houses' where
you're supposed to tune your radio to a given station and get information on
why you want to drop a quarter million bucks on a thousand square feet of
your very own sometime in the next 20 minutes... except he doesn't want
people to have to tune at all!

Slightly less evil would be emergency broadcasting type uses...

---Joel Kolstad

In article , "Michael A. Terrell" wrote:
duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel. The big question is why you would want to
do it.

You could generate it at one channel in the middle of the band then sample it
at 200 kHz to create replica spectra at the 200 kHz spacing. Probably will
need to keep the sampling pulse relatively narrow to avoid too much sinc(x)
roll-off. Any amplifiers after that point would need to support the entire
bandwidth.

Dr. G.

In article , "Michael A. Terrell" wrote:
duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Not with a single transmitter. You could build a comb generator and
modulate it for AM, but the quality would be poor For FM you either need
separate transmitters, or modulate the signal and mix it with a separate
oscillator for each channel. The big question is why you would want to
do it.

You could generate it at one channel in the middle of the band then sample it
at 200 kHz to create replica spectra at the 200 kHz spacing. Probably will
need to keep the sampling pulse relatively narrow to avoid too much sinc(x)
roll-off. Any amplifiers after that point would need to support the entire
bandwidth.

Dr. G.

Joel Kolstad wrote:
Michael A. Terrell wrote:

duckman wrote:

Is there available, can it be done to have an AM and/ and or FM
transmitter that will broadcast over the entire AM and FM broadcast band
at the same time. Or at least multiple stations. E.G.

Slightly less evil would be emergency broadcasting type uses...

Apparently someone believes it's possible as an application was recently
filed with the FCC for an experimental license to operate just such a
system across the FM band. (the Commission denied the application)

Their intent was to install transmitters on emergency vehicles, so they
could warn other motorists to get out of the way.

My guess is the FCC feared these devices would "get out into the wild" -
can you imagine what an unscrupulous nightclub owner (or someone with
a political bone to pick) could do with a few of these?
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Joel Kolstad wrote:
Michael A. Terrell wrote:

duckman wrote:

Is there available, can it be done to have an AM and/ and or FM
transmitter that will broadcast over the entire AM and FM broadcast band
at the same time. Or at least multiple stations. E.G.

Slightly less evil would be emergency broadcasting type uses...

Apparently someone believes it's possible as an application was recently
filed with the FCC for an experimental license to operate just such a
system across the FM band. (the Commission denied the application)

Their intent was to install transmitters on emergency vehicles, so they
could warn other motorists to get out of the way.

My guess is the FCC feared these devices would "get out into the wild" -
can you imagine what an unscrupulous nightclub owner (or someone with
a political bone to pick) could do with a few of these?
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

If you want to put up a signal that covers a wide band, you will
essentially need a spreading function. In your case, there is no
corelation that will de-spread the signal at the receiving end, now,
regardless of the technique you employ to achieve this transmission,
one thing is sure, you will need some really heavy power.

imagine that you can cover 300 meters using a 10mW transmitter. Now,
this transmission is received by a receiver with a selectivity of
about 50KHz. If you were to cover such a signal every 50KHz for 1MHz,
you will require 1000/50 = 20 times as much power, that is, about
500mW. Correspondingly, if you wanted to transmit over a 10MHz
bandwidth, you will require 5Watts output to achieve the same result.

Now, lets move onto the next part: what kind of modulation? Frequency
modulation requires that the carrier should shift. Therefore, if you
modulated broadband noise, it wouldn't do. You will have to put out
carriers every 50KHz. This will require a comb generator. Hers is how,
pass the carrier through an XOR gate and feed the other input of the
XOR gate with a 50KHz carrier. This will keep flipping the phase by
180% and generate sidebands. The strength of the side bands will
depend upon how square your 50KHz carrier is. The carrier can be
frequency modulated as normally done.

This is a quick and dirty method. there are a number of problems with
this approach, first, there is really no way of limiting the signals
to a particular band unless you do extensive amount of filtering at
the output. second, the signals will be the strongest in the center
and taper off exponentially (not really, but actually) towards the
edges of the band.

If you want to put up a signal that covers a wide band, you will
essentially need a spreading function. In your case, there is no
corelation that will de-spread the signal at the receiving end, now,
regardless of the technique you employ to achieve this transmission,
one thing is sure, you will need some really heavy power.

imagine that you can cover 300 meters using a 10mW transmitter. Now,
this transmission is received by a receiver with a selectivity of
about 50KHz. If you were to cover such a signal every 50KHz for 1MHz,
you will require 1000/50 = 20 times as much power, that is, about
500mW. Correspondingly, if you wanted to transmit over a 10MHz
bandwidth, you will require 5Watts output to achieve the same result.

Now, lets move onto the next part: what kind of modulation? Frequency
modulation requires that the carrier should shift. Therefore, if you
modulated broadband noise, it wouldn't do. You will have to put out
carriers every 50KHz. This will require a comb generator. Hers is how,
pass the carrier through an XOR gate and feed the other input of the
XOR gate with a 50KHz carrier. This will keep flipping the phase by
180% and generate sidebands. The strength of the side bands will
depend upon how square your 50KHz carrier is. The carrier can be
frequency modulated as normally done.

This is a quick and dirty method. there are a number of problems with
this approach, first, there is really no way of limiting the signals
to a particular band unless you do extensive amount of filtering at
the output. second, the signals will be the strongest in the center
and taper off exponentially (not really, but actually) towards the
edges of the band.

This needs clarification. Do you mean that it will generate multiple
carriers? Like this?

At the same time the output has carriers @ 88.1 and 88.3 and 88.5 and
88.7.....97.5 and 97.7 and 97.9 ????

Actually this is possible if you
can make the proper circuitry. An oscillator FM modulated with a 200 KHz
signal will do it. You just need enough deviation. You could also add in
the audio modulation.

Forgot to mention that I've done it.

Steve

k;9;d;c;i

"duckman" wrote in message
...
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM
transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

This needs clarification. Do you mean that it will generate multiple
carriers? Like this?

At the same time the output has carriers @ 88.1 and 88.3 and 88.5 and
88.7.....97.5 and 97.7 and 97.9 ????

Actually this is possible if you
can make the proper circuitry. An oscillator FM modulated with a 200 KHz
signal will do it. You just need enough deviation. You could also add in
the audio modulation.

Forgot to mention that I've done it.

Steve

k;9;d;c;i

"duckman" wrote in message
...
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM
transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Conceptually, you're describing something similar to
ODFM, used in 802.11(a) and (g). Basically, you create
numerous independently modulated carriers across a band,
combine them and amplify them. If you're intent on
transmitting the same information on each carrier, then I
suppose a simplifying trick might be to produce a comb,
but the general case is basically identical to something
that exists already.

Now, here's a question that follows - suppose you built
an ODFM transmitter that was able to place a signal on
each 'channel' in the FM broadcast band. What could
power-level/signal-strength would be permitted under
Part 15? Would the aggregate ODFM signal be considered a
single signal for Part 15 purposes, or would each 'channel'
be considered an independent signal (since, technically, it
is)?


Dana

duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Conceptually, you're describing something similar to
ODFM, used in 802.11(a) and (g). Basically, you create
numerous independently modulated carriers across a band,
combine them and amplify them. If you're intent on
transmitting the same information on each carrier, then I
suppose a simplifying trick might be to produce a comb,
but the general case is basically identical to something
that exists already.

Now, here's a question that follows - suppose you built
an ODFM transmitter that was able to place a signal on
each 'channel' in the FM broadcast band. What could
power-level/signal-strength would be permitted under
Part 15? Would the aggregate ODFM signal be considered a
single signal for Part 15 purposes, or would each 'channel'
be considered an independent signal (since, technically, it
is)?


Dana

duckman wrote:
something suspicious

I've been to about 5 different radio related groups this morning lurking
for information about a problem I have in a similar field to this duckman
guy, and (1) his request has been -- identically worded, if not mistaken
-- in each of the groups I've read, a couple related to pirate radio, a
couple related to professional broadcast radio, and a couple related to
ham radio. What gives?

Anywhoo, I've got a similar question I post shortly.

I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

duckman wrote:
something suspicious

I've been to about 5 different radio related groups this morning lurking
for information about a problem I have in a similar field to this duckman
guy, and (1) his request has been -- identically worded, if not mistaken
-- in each of the groups I've read, a couple related to pirate radio, a
couple related to professional broadcast radio, and a couple related to
ham radio. What gives?

Anywhoo, I've got a similar question I post shortly.

I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.


"Circuit Breaker" wrote in message
. ..
I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.


"Circuit Breaker" wrote in message
. ..
I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

Ghost Writer wrote:

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.

;-) Google for: hearing aid "Mel Tillis"

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

Ghost Writer wrote:

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.

;-) Google for: hearing aid "Mel Tillis"

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!

In article , Wim Lewis
wrote:

In article ,
duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

Do you want to broadcast a large number of different signals simultaneously
from the same transmitter, or many copies of the same signal?

Both should be pretty straightforward to do... if you want to broadcast
many copies of the same signal, you could just replace the LO with
a circuit that generates a number of carriers, superimposed. Each
frequency component in the LO will produce a corresponding copy of the
audio signal in the RF or IF output.

I don't know if it's possible to broadcast a single audio signal spread
over a wide band (instead of having one copy at each standard AM station
frequency, as above). My intuition says it should be possible to
amplitude-modulate some wideband noise, and any AM receiver with an
envelope detector would recover the signal. But mathematically, I'm not
so sure --- where would the sidebands go, how would the receiver
distinguish them from the overlapping "carrier"? Or could this be
thought of as a sort of self-despreading spread spectrum signal?
Perhaps I should just go to bed ...





If you just want to jam, build a 10.7 MHz transmitter and turn it on when
desired. Most cheap radios don't have good IF rejection and the signal
will capture the normally weak incoming signal from the broadcast.
However, the whole thing is illegal no matter what the method.

Steve

In article , Wim Lewis
wrote:

In article ,
duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

Do you want to broadcast a large number of different signals simultaneously
from the same transmitter, or many copies of the same signal?

Both should be pretty straightforward to do... if you want to broadcast
many copies of the same signal, you could just replace the LO with
a circuit that generates a number of carriers, superimposed. Each
frequency component in the LO will produce a corresponding copy of the
audio signal in the RF or IF output.

I don't know if it's possible to broadcast a single audio signal spread
over a wide band (instead of having one copy at each standard AM station
frequency, as above). My intuition says it should be possible to
amplitude-modulate some wideband noise, and any AM receiver with an
envelope detector would recover the signal. But mathematically, I'm not
so sure --- where would the sidebands go, how would the receiver
distinguish them from the overlapping "carrier"? Or could this be
thought of as a sort of self-despreading spread spectrum signal?
Perhaps I should just go to bed ...





If you just want to jam, build a 10.7 MHz transmitter and turn it on when
desired. Most cheap radios don't have good IF rejection and the signal
will capture the normally weak incoming signal from the broadcast.
However, the whole thing is illegal no matter what the method.

Steve

On Tue, 09 Dec 2003 10:51:45 +1100, duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Yes there are such animals out on the commercial market. It's often used
for emergency radio systems in tunnels ( like the Alp tunnels! ) Where you
have the need to send on all frequencies if something goes awry!

Mostly on the AM band but I think the same method is used for the FM band
as well. Ans yes, they use only one transmitter!

The basic principle is to take all available channels, 25 or 50 kc
separation. take the output
from all those channels and superimpose them on one signal carrier. The
resulting 'waveform' will then contain al channels and you just modulate
it and feed it to a broadband amplifier. For the AM broadband transmitter,
this is done by sampling the resulting signal and store it on an eprom
and use that as the input to generate a multifrequency signal.

Remember the old G3RUH modulation for 9600 baud, where its many
frequencies put together to generate the composite signal, which can be
taken apart by a receiver again.


Cheers

Sorry if this sounds weird, but if you wanna listen to the real case, just
drive down in the europe alp tunnels!

On Tue, 09 Dec 2003 10:51:45 +1100, duckman wrote:

Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.

Yes there are such animals out on the commercial market. It's often used
for emergency radio systems in tunnels ( like the Alp tunnels! ) Where you
have the need to send on all frequencies if something goes awry!

Mostly on the AM band but I think the same method is used for the FM band
as well. Ans yes, they use only one transmitter!

The basic principle is to take all available channels, 25 or 50 kc
separation. take the output
from all those channels and superimpose them on one signal carrier. The
resulting 'waveform' will then contain al channels and you just modulate
it and feed it to a broadband amplifier. For the AM broadband transmitter,
this is done by sampling the resulting signal and store it on an eprom
and use that as the input to generate a multifrequency signal.

Remember the old G3RUH modulation for 9600 baud, where its many
frequencies put together to generate the composite signal, which can be
taken apart by a receiver again.


Cheers

Sorry if this sounds weird, but if you wanna listen to the real case, just
drive down in the europe alp tunnels!