Wireless AM analog internet connections?

Hi:

What would be the disadvantages of using analog amplitude modulation
[similar to AM radio] at 300 MHz frequency for wireless internet
connections? Let's say the modulator signal is attenuated [to prevent
clipping due to excess signal amplitude and to prevent interference
with nearby station] prior to D-A conversion and transmission. At the
receiving end, the carrier signal is amplified [so it can be
recognized by the receiving computer] prior to demodulation and A-D
conversion. In addition, the receiver is DXed. DX is a radio technique
to receiving distant stations.

What would be the disadvantages of such a wireless internet
connection?

Would there be any differences at night?


Thanks,

Radium



Radium

Radium <(E-Mail Removed)> hath wroth:

>What would be the disadvantages of using analog amplitude modulation
>[similar to AM radio] at 300 MHz frequency for wireless internet
>connections?

At 2.4GHz, Wi-Fi requires about 22Mhz occupied bandwidth to move
54Mbits/sec raw data rate. At 300MHz, there is no service that will
allow you to monopolize 22Mhz bandwidth. The bandwidth problem also
applies to antennas, where keeping the VSWR reasonable over the 22Mhz
bandwidth at 300MHz is difficult.

Also, if you're planning to do this without a license, on top of
existing users, I'll be the first to turn you in to the FCC
enforcement burro.

>Let's say the modulator signal is attenuated [to prevent
>clipping due to excess signal amplitude and to prevent interference
>with nearby station] prior to D-A conversion and transmission. At the
>receiving end, the carrier signal is amplified [so it can be
>recognized by the receiving computer] prior to demodulation and A-D
>conversion.

Ummm... This is gibberish. Try again please.

802.11 at 1 and 2 Mbits/sec is pure PM (phase modulation). There's no
AM component. However, all other higher speeds combine a mixture PM
and AM to maximize the spectral efficiency in bits/Hz. If you were to
try this with pure AM, in the same 22Mhz bandwidth, you would waste
50% of your power on the carrier, and half again in each of the two
symmetrical sidebands. I'm too lazy to calculate the exact number,
but my guess is that you would get about 4Mbits/sec maximum data rate
with pure AM in 22MHz occupied bandwidth.

Note that there are systems that actually do use pure AM and its close
relative on/off keying. The advantage is that it's fairly easy to
compensate for doppler shift effects. RFID is a good example.

>In addition, the receiver is DXed. DX is a radio technique
>to receiving distant stations.

Nope. DX is the art of exchanging useless information with a distant
station, via a weak signal, out of a mess of noise, using rather
expensive equipment, in the presense of interference from hundreds of
other DX'ers, for the sole purpose of obtaining QSL cards, that
substitute for wallpaper. More generally, DX is a sport.

>What would be the disadvantages of such a wireless internet
>connection?

1. It won't have the capacity of a system that uses both PM and AM.
2. It won't be legal.
3. It will have bandwidth restrictions due to the lower frequency
that will substantially lower thruput.
4. It will interfere with existing services on the frequencies you
plan to trash.
5. It will not be backed by a reputeable standards group.
6. It pisses me off.

>Would there be any differences at night?

No. Doing this under the cover of darkness will not make it work or
prevent getting caught.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Radium <(E-Mail Removed)> hath wroth:
..
>
>>In addition, the receiver is DXed. DX is a radio technique
>>to receiving distant stations.
>
> Nope. DX is the art of exchanging useless information with a distant
> station, via a weak signal, out of a mess of noise, using rather
> expensive equipment, in the presense of interference from hundreds of
> other DX'ers, for the sole purpose of obtaining QSL cards, that
> substitute for wallpaper. More generally, DX is a sport.

This is an excellent description
>
>>What would be the disadvantages of such a wireless internet
>>connection?
>
> 1. It won't have the capacity of a system that uses both PM and AM.
> 2. It won't be legal.
> 3. It will have bandwidth restrictions due to the lower frequency
> that will substantially lower thruput.
> 4. It will interfere with existing services on the frequencies you
> plan to trash.
> 5. It will not be backed by a reputeable standards group.
> 6. It pisses me off.
>
>>Would there be any differences at night?
>
> No. Doing this under the cover of darkness will not make it work or
> prevent getting caught.
>
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

On May 24, 11:39 pm, Jeff Liebermann <j...@comix.santa-cruz.ca.us>
wrote:

> Radium <gluceg...@gmail.com> hath wroth:
>
> >What would be the disadvantages of using analog amplitude modulation
> >[similar to AM radio] at 300 MHz frequency for wireless internet
> >connections?
>
> At 2.4GHz, Wi-Fi requires about 22Mhz occupied bandwidth to move
> 54Mbits/sec raw data rate. At 300MHz, there is no service that will
> allow you to monopolize 22Mhz bandwidth. The bandwidth problem also
> applies to antennas, where keeping the VSWR reasonable over the 22Mhz
> bandwidth at 300MHz is difficult.

What if the carrier frequency is 300 GHz instead of 300 MHz?

Also, if all wireless hot-spots were to use 300 GHz analog amplitude
modulation, would this be a problem?

> >Let's say the modulator signal is attenuated [to prevent
> >clipping due to excess signal amplitude and to prevent interference
> >with nearby station] prior to D-A conversion and transmission. At the
> >receiving end, the carrier signal is amplified [so it can be
> >recognized by the receiving computer] prior to demodulation and A-D
> >conversion.
>
> Ummm... This is gibberish. Try again please.
>
> 802.11 at 1 and 2 Mbits/sec is pure PM (phase modulation). There's no
> AM component. However, all other higher speeds combine a mixture PM
> and AM to maximize the spectral efficiency in bits/Hz. If you were to
> try this with pure AM, in the same 22Mhz bandwidth, you would waste
> 50% of your power on the carrier, and half again in each of the two
> symmetrical sidebands. I'm too lazy to calculate the exact number,
> but my guess is that you would get about 4Mbits/sec maximum data rate
> with pure AM in 22MHz occupied bandwidth.

So most wireless telecommunications use PM?

> Note that there are systems that actually do use pure AM and its close
> relative on/off keying. The advantage is that it's fairly easy to
> compensate for doppler shift effects. RFID is a good example.

The on/off you describe is digital. I am asking about analog AM.

> >In addition, the receiver is DXed. DX is a radio technique
> >to receiving distant stations.
>
> Nope. DX is the art of exchanging useless information with a distant
> station, via a weak signal, out of a mess of noise, using rather
> expensive equipment, in the presense of interference from hundreds of
> other DX'ers, for the sole purpose of obtaining QSL cards, that
> substitute for wallpaper. More generally, DX is a sport.

DXing increases the reception of heterodynes. How do heterodynes
affect wireless networks running on analog amplitude modulation radio
signals?

> >What would be the disadvantages of such a wireless internet
> >connection?
>
> 1. It won't have the capacity of a system that uses both PM and AM.

Okay.

> 3. It will have bandwidth restrictions due to the lower frequency
> that will substantially lower thruput.

Okay. So use 300 GHz AM instead.

> 4. It will interfere with existing services on the frequencies you
> plan to trash.

Not if the signals are strongly attenuated prior to transmission.

> 5. It will not be backed by a reputeable standards group.

I am asking about the scientific disadvantages, not the social, legal,
or political drawbacks.

> >Would there be any differences at night?
>
> No. Doing this under the cover of darkness will not make it work or
> prevent getting caught.

It's not a matter of getting caught. I am asking because I notice
heterodynes to be louder on the AM radio at night while much softer
[sometimes even absent] during the day.

On 25 May 2007 16:08:13 -0700, in alt.internet.wireless , Radium
<(E-Mail Removed)> wrote:

>On May 24, 11:39 pm, Jeff Liebermann <j...@comix.santa-cruz.ca.us>
>wrote:
>
>> Radium <gluceg...@gmail.com> hath wroth:
>>
>> >What would be the disadvantages of using analog amplitude modulation
>> >[similar to AM radio] at 300 MHz frequency for wireless internet
>> >connections?
>>
>> At 2.4GHz, Wi-Fi requires about 22Mhz occupied bandwidth to move
>> 54Mbits/sec raw data rate. At 300MHz, there is no service that will
>> allow you to monopolize 22Mhz bandwidth. The bandwidth problem also
>> applies to antennas, where keeping the VSWR reasonable over the 22Mhz
>> bandwidth at 300MHz is difficult.
>
>What if the carrier frequency is 300 GHz instead of 300 MHz?

You're nudging the point at which the atmosphere is opaque.
Atmospheric conditions will also start to mess seriously with your
signal.

--
Mark McIntyre

Radium <(E-Mail Removed)> hath wroth:

>What if the carrier frequency is 300 GHz instead of 300 MHz?

300Ghz is almost optical. Officially, it's sub-millimeter microwave.
You could not afford the hardware. It's mostly MASER and LASER based.
The FCC setup (and sold) the 30GHz LMDS band and service for local
distribution. Very few systems are deployed because of the limited
range, very expensive hardware, and inability to penetrate anything.
The good news is that you probably would not interfere with anyone at
300GHz. Oh yeah, the world ham DX record at 300GHz is about 10km.

>Also, if all wireless hot-spots were to use 300 GHz analog amplitude
>modulation, would this be a problem?

No problem if you don't mind carrying a rather large pile of
waveguide, a pair of dish antennas, and can tolerate a typical range
of a few cm.

>So most wireless telecommunications use PM?

Most wireless starts with PM. It's cheap, easy, cheap, reliable,
cheap, and by the way, cheap. However, to squeeze more data in the
same occupied bandwidth, an amplitude component is added on top of the
PM. Start reading here:
<http://en.wikipedia.org/wiki/Modulation>

>The on/off you describe is digital. I am asking about analog AM.

Wrong. It is very difficult to distinguish between analog and digital
modulation. For example, I have a class E linear amplifier design for
AM and SSB. Digital techniques for analog modes. See the list of
modes at:
<http://en.wikipedia.org/wiki/Modulation>
in the box on the right. Note that they are divided into Analog,
Digital, MUX, and Spread Spectrum. Note that some modes, such as QAM,
appear as both digital and analog. I'm not sure I agree that OFDM
should be classified as MUX instead of Spread Spectrum. Anyway, don't
worry about whether it's digital or analog.

You seem to have some attachment to AM modultion. Let me just say
that there's a reason that AM was first to be invented. It's very
easy to generate and detect, but has serious limitations. The worst
is that half the power is wasted in the carrier. That puts AM at a
serious disadvantage to other methods over spectral efficiency and
power efficiency. It's no accident that FM and SSB were invented
shortly after AM was determined to inadequate. The various digital
modes followed soon after in order to improve spectral efficiency even
more. See:
<http://en.wikipedia.org/wiki/Spectral_efficiency>
Trying to run a wireless system on AM would be like turning back the
clock of progress 80 years.

>DXing increases the reception of heterodynes. How do heterodynes
>affect wireless networks running on analog amplitude modulation radio
>signals?

Hetrodynes are a method of mixing two frequencies to produce a 3rd
frequency. It has nothing to do with channel carrying capacity, the
modulation mode, or the distances (DX) involved. More specifically,
absolutely NOTHING inherent in the modulation or occupied bandwidth
has any relation to the distances (DX) involved.

>I am asking about the scientific disadvantages, not the social, legal,
>or political drawbacks.

Well, feel free to ignore the social, legal, and political issues and
see how far you get. We had a local bootleg microwave link that was
trashing communications. We also has a clown running about 10 watts
ERP on his 2.4GHz cordless phone in the downtown area. I've also seen
overpowered 2.4GHz 802.11b/g systems. I was involved in taking them
off the air.

>It's not a matter of getting caught. I am asking because I notice
>heterodynes to be louder on the AM radio at night while much softer
>[sometimes even absent] during the day.

Sure. At 1MHz, propagation issues are paramount. That's why AM
broadcast stations vary their power during daylight and nightime
operation. Different frequency bands have different characteristics
during different times of the day. They are also affected by
atmospheric ionization depending on whether the sun is visible or
below the horizon. Start reading about RF propagation here:
<http://en.wikipedia.org/wiki/Radio_propagation>

However, ionospheric effects disappear above the MUF (maximum usable
frequency) or about 25MHz maximum. For VHF, UHF, and various
microwave frequencies, propagation is mostly affected by simple
inverse square law and atmospheric oxygen and water absorption. See
curves at:
<http://www.microwaves101.com/encyclopedia/frequency.cfm>
The trick is to pick a frequency that doesn't get easily absorbed.
That's not easy as all the good ones are already taken.

You haven't bothered to disclose what you're trying to accomplish, but
that ok. I can answer your questions in general terms. Before you
attempt to do anything new in the area of wireless, methinks you
should assemble a suitable background and experience level using
existing technology. That will save you the frustration of building
something that can't be deployed due to technical or legal
limitations.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Radium" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> On May 24, 11:39 pm, Jeff Liebermann <j...@comix.santa-cruz.ca.us>
> wrote:
>
>> Radium <gluceg...@gmail.com> hath wroth:
>>
>> >What would be the disadvantages of using analog amplitude modulation
>> >[similar to AM radio] at 300 MHz frequency for wireless internet
>> >connections?
>>
>> At 2.4GHz, Wi-Fi requires about 22Mhz occupied bandwidth to move
>> 54Mbits/sec raw data rate. At 300MHz, there is no service that will
>> allow you to monopolize 22Mhz bandwidth. The bandwidth problem also
>> applies to antennas, where keeping the VSWR reasonable over the 22Mhz
>> bandwidth at 300MHz is difficult.
>
> What if the carrier frequency is 300 GHz instead of 300 MHz?
>
> Also, if all wireless hot-spots were to use 300 GHz analog amplitude
> modulation, would this be a problem?
>
>> >Let's say the modulator signal is attenuated [to prevent
>> >clipping due to excess signal amplitude and to prevent interference
>> >with nearby station] prior to D-A conversion and transmission. At the
>> >receiving end, the carrier signal is amplified [so it can be
>> >recognized by the receiving computer] prior to demodulation and A-D
>> >conversion.
>>
>> Ummm... This is gibberish. Try again please.
>>
>> 802.11 at 1 and 2 Mbits/sec is pure PM (phase modulation). There's no
>> AM component. However, all other higher speeds combine a mixture PM
>> and AM to maximize the spectral efficiency in bits/Hz. If you were to
>> try this with pure AM, in the same 22Mhz bandwidth, you would waste
>> 50% of your power on the carrier, and half again in each of the two
>> symmetrical sidebands. I'm too lazy to calculate the exact number,
>> but my guess is that you would get about 4Mbits/sec maximum data rate
>> with pure AM in 22MHz occupied bandwidth.
>
> So most wireless telecommunications use PM?
>
>> Note that there are systems that actually do use pure AM and its close
>> relative on/off keying. The advantage is that it's fairly easy to
>> compensate for doppler shift effects. RFID is a good example.
>
> The on/off you describe is digital. I am asking about analog AM.

The on/off he described is not considered digital.

>
>> >In addition, the receiver is DXed. DX is a radio technique
>> >to receiving distant stations.
>>
>> Nope. DX is the art of exchanging useless information with a distant
>> station, via a weak signal, out of a mess of noise, using rather
>> expensive equipment, in the presense of interference from hundreds of
>> other DX'ers, for the sole purpose of obtaining QSL cards, that
>> substitute for wallpaper. More generally, DX is a sport.
>
> DXing increases the reception of heterodynes.

Dxing, does no such thing.
As described DXing is as described above.


>
>> >What would be the disadvantages of such a wireless internet
>> >connection?
>>
>> 1. It won't have the capacity of a system that uses both PM and AM.
>
> Okay.
>
>> 3. It will have bandwidth restrictions due to the lower frequency
>> that will substantially lower thruput.
>
> Okay. So use 300 GHz AM instead.

Keep thinking like you do.
>
>> 4. It will interfere with existing services on the frequencies you
>> plan to trash.
>
> Not if the signals are strongly attenuated prior to transmission.

Than it would be useless
>
>> 5. It will not be backed by a reputeable standards group.
>
>> >Would there be any differences at night?
>>
>> No. Doing this under the cover of darkness will not make it work or
>> prevent getting caught.
>
> It's not a matter of getting caught. I am asking because I notice
> heterodynes to be louder on the AM radio at night while much softer
> [sometimes even absent] during the day.

You really have no clue.
What you describe is a function of the frequencies used, not the
"heterodynes"

>

On May 25, 7:01 pm, "Dana" <raff...@yahoo.com> wrote:

> "Radium" <gluceg...@gmail.com> wrote in message
>
> news:(E-Mail Removed) oups.com...

> > Not if the signals are strongly attenuated prior to transmission.
>
> Than it would be useless

Not if the reciever sufficiently-amplifies the carrier wave prior to
demodulation.

"Radium" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> On May 25, 7:01 pm, "Dana" <raff...@yahoo.com> wrote:
>
>> "Radium" <gluceg...@gmail.com> wrote in message
>>
>> news:(E-Mail Removed) oups.com...
>
>> > Not if the signals are strongly attenuated prior to transmission.
>>
>> Than it would be useless
>
> Not if the reciever sufficiently-amplifies the carrier wave prior to
> demodulation.

If you strongly attenuate your signal prior to transmission, unless you use
a super cooled receiver, the range of your system would be useless.
In other words, you would not have a viable system.
>

Radium <(E-Mail Removed)> hath wroth:

>On May 25, 7:01 pm, "Dana" <raff...@yahoo.com> wrote:
>
>> "Radium" <gluceg...@gmail.com> wrote in message
>>
>> news:(E-Mail Removed) oups.com...
>
>> > Not if the signals are strongly attenuated prior to transmission.
>>
>> Than it would be useless
>
>Not if the reciever sufficiently-amplifies the carrier wave prior to
>demodulation.

Useless. Once again, you can't use techniques that work at AM
broadcast frequencies at microwave frequencies.

You can get away with attenuating the receive signal at frequencies
below about 7MHz because the atmospheric noise (mostly from lightning
hits) is so much higher than the receiver front end noise level. It
makes not sense to have a very low noise front end when all you're
amplifying is atmospheric noise. At higher frequencies, the front end
noise and later the thermal noise increases faster than the gain of
the front end amplifier. The result is that at microwave frequencies,
the bulk of design effort is overcoming the base line noise level,
while still retaining enough dynamic range to produce a useful
product.

This might help:
<http://www.maxim-ic.com/appnotes.cfm/an_pk/1836>



--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558