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.