ELF radio needs more watts than MW radio?

[Green Xenon [Radium]]

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?


Thanks,

Radium

 

[Jamie]

Green Xenon [Radium] wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?


Thanks,

Radium
I know this is the BASIC channel how ever, All I can say is WOW!

--
"I'd rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

 

[Sjouke Burry]

Jamie wrote:

wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?


Thanks,

Radium
I know this is the BASIC channel how ever, All I can say is WOW!



What do you expect from radium trolling?

 

[Sam Wormley]

Green Xenon [Radium] wrote:

radio
transmission is inefficient because it requires to[o] much power.

That's bullshit.

 

[Eric Gisse]

On Jul 24, 4:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com>
wrote:
[snip]

This kid suffers a terminal case of "doesn't know what he is talking
about".

 

[Michael Black]

On Fri, 25 Jul 2008, Spaceman wrote:

wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

True and not true.
Maybe this will help shed some ELF light on the subject.
http://en.wikipedia.org/wiki/Extremely_low_frequency

Of course, that's not an inefficiency of spectrum.

And the inefficiency of the long antennas means nothing since
such low frequencies are used for specific purposes where such
low frequencies are the only choices. Given that, the only
choice is to use such low frequencies, or not communicate
at all.

Michael

 

On Jul 25, 12:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com>
wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Thanks,

Radium

There is the modulation method - AM or FM. FM is more efficient - at
least narrowband FM. That's why we use FM for mobile transmitters. You
could use supressed-carrier AM of course but that is a sod to
demodulated.

The higher the frequency the shorter the distance it can travel for a
given power. Therefore VLF can travel round the world and back again!
trouble is you may need for ELF an aerial the size of a mountain
range!
For a 10 Gig frenquency you would need to pump out a heluva lot of
power for it to go any distance. Inverse square law.


Would help of you went to study engineering at Uni - then most of your
questions would be answered.

K.

 

[hhc314@yahoo.com]

On Jul 25, 8:53 am, NoS...@daqarta.com (Bob Masta) wrote:

"

glucege...@gmail.com> wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

I suspect what you actually read about was the US military scheme to
communicate with submerged submarines using high-power VLF that could
penetrate seawater.  At one point there were plans to use huge
underground ore veins in Michigan's Upper Penninsula as the
transmitter antenna.  That might have been a tad inefficient!

There's also the issue of low carrier frequencies not supporting high
symbol rates.  I seem to recall that the submerged subs would get only
code, at rates so slow even the rankest beginning amateur operator
would have had no trouble keeping up... <g

Best regards,

Bob Masta

              DAQARTA  v4.00
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
           FREE Signal Generator
        Science with your sound card!

Shush Bob, you're deliving into 100% reliable long distance
communications techniques first discovered and exploited in the 1950s
and which have remained classified ever since. As you point out, the
information transmission rate is incredibly low, but extremely
reliable and nearly impossible to block or jam, and it reliably
reaches every location on earth, surface, underwater, or underground,
at extremely low baud rates.

Now what would anyone imagine what purpose such a limited system might
be used for? This is precisely why VLF systems of this type remain
highly classified. Yes, correct. They have only one practical
application. Let's simply call it the Fed Ex principle, which applies
to things that must be reliably delivered on schedule.

Harry C.

 

[Igor]

On Jul 24, 8:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com>
wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Thanks,

Radium

I'm not sure about output power, but I do know that the lower the
frequency, the longer the wavelength, and hence the longer the
transmitting antenna. ELF requires a humongous antenna.

 

On Jul 26, 11:05 am, j...@specsol.spam.sux.com wrote:

In sci.physics kronec...@yahoo.co.uk wrote:
On Jul 25, 12:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com
wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Thanks,

Radium
There is the modulation method - AM or FM. FM is more efficient - at
least narrowband FM. That's why we use FM for mobile transmitters. You
could use supressed-carrier AM of course but that is a sod to
demodulated.

Nonsense.

FM is common because it is intrinsically immune to impulse noise
and cheap to implement.

It's cheap but not immune to noise and suseptable to multipath big-

time.

Supressed carrier is trivial to demodulate these days but more
expensive to do.

Do tell how...It's not in any text book so maybe we can learn with

your advanced knowledge.

The higher the frequency the shorter the distance it can travel for a
given power. Therefore VLF can travel round the world and back again!

Nonsense.

Most long distance terrestrial communication is done on HF.

You have never heard of the inverse square law obviously. High

frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

trouble is you may need for ELF an aerial the size of a mountain
range!

About the only thing you got right.

The only thing we agree on - you must be a physicist - no idea about

engineering.


As for your moon thing - it's line of site again!! Try communicating
from London to New York at 10GHz.


Idiot.


K.

 

[John Larkin]

On Thu, 24 Jul 2008 17:31:55 -0700 (PDT), "Green Xenon [Radium]"
<glucegen1x@gmail.com> wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

Sure; for constant photon rates, one transmitter is outputting, say, 1
million watts, and the other is doing 1 watt. But broadcasters don't
pay for photons, they pay for watts.

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Any transmitter can run at any power level, and photons don't matter.
The problem with ELF is that an efficient antenna is enormous, and elf
waves don't bounce off the ionosphere like mw waves do, so most of the
energy cruises right out into space.

Huge elf rigs were/are used for loran-C, WWVB, and communicating with
atomic subs. They use inefficient ground-wave propagation, so need
huge power levels. The loran-C station north of San Francisco is about
100 KHz at some megawatts peak power.

Really, you should look some of this stuff up.

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

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




Read "Tuxedo Park"...

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


John

 

[Michael Black]

On Sat, 26 Jul 2008, John Larkin wrote:

"
glucegen1x@gmail.com> wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

Sure; for constant photon rates, one transmitter is outputting, say, 1
million watts, and the other is doing 1 watt. But broadcasters don't
pay for photons, they pay for watts.


So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Any transmitter can run at any power level, and photons don't matter.
The problem with ELF is that an efficient antenna is enormous, and elf
waves don't bounce off the ionosphere like mw waves do, so most of the
energy cruises right out into space.

Huge elf rigs were/are used for loran-C, WWVB, and communicating with
atomic subs. They use inefficient ground-wave propagation, so need
huge power levels. The loran-C station north of San Francisco is about
100 KHz at some megawatts peak power.

Not really. They use frequencies that will have good penetration, and

which don't suffer much from radio conditions.

Because the frequencies are so low, that ground-wave will be considerable,
while higher frequencies need to bounce off the ionosphere and such to
get the same sort of distance. But that is unreliable, and of course
often is dependent on the time of the day.

Those frequencies are terribly reliable, interference aside.

Once that choice is made, then they have to live with the inefficiencey.
They have decided there is no other choice for their needs, and then
compensate with the high power to overcome the inefficiency of the
antennas.

As an example, there's a broadcast station in Ottawa on 580KHz that
comes in fine during the day. But at night, they are required to
cut back on their power, so the station goes away, not enough power
for ground wave to Montreal, while bouncing off the ionosphere
results in a bounce too far away. They have to cut back their power at
night so the better propagation at night does not leave them with
a booming signal bouncing off the ionosphere to interfere with all
the other stations on that frequency. I'm sure there are plenty of
locations much further away that can receive the station at night,
that can't receive it at night (after all, I can hear plenty of AM
broadcast stations at night from much further away that I could never
hear during the daytime). I did receive the Ottawa station at night
during one period a decade ago, when an emergency situation allowed
them to run full power at night; ground wave reception was fine.

So they run WWVB and such at low frequencies so the reliable ground
wave is used for really long distances (I can receive it fine here
in Montreal, I've had an "atomic clock" for almost five years and
rarely does it not sync up at night). One can argue that their
high power is not just because of the inefficient antennas at 60KHz,
but so it is receivable so far away, just like that Ottawa station
where the ground wave signal disappears when they lower their power.

Michael

 

[John Larkin]

On Sat, 26 Jul 2008 14:12:25 -0400, Michael Black <et472@ncf.ca>
wrote:

On Sat, 26 Jul 2008, John Larkin wrote:

On Thu, 24 Jul 2008 17:31:55 -0700 (PDT), "Green Xenon [Radium]"
glucegen1x@gmail.com> wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

Sure; for constant photon rates, one transmitter is outputting, say, 1
million watts, and the other is doing 1 watt. But broadcasters don't
pay for photons, they pay for watts.


So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Any transmitter can run at any power level, and photons don't matter.
The problem with ELF is that an efficient antenna is enormous, and elf
waves don't bounce off the ionosphere like mw waves do, so most of the
energy cruises right out into space.

Huge elf rigs were/are used for loran-C, WWVB, and communicating with
atomic subs. They use inefficient ground-wave propagation, so need
huge power levels. The loran-C station north of San Francisco is about
100 KHz at some megawatts peak power.

Not really. They use frequencies that will have good penetration, and
which don't suffer much from radio conditions.

Because the frequencies are so low, that ground-wave will be considerable,
while higher frequencies need to bounce off the ionosphere and such to
get the same sort of distance. But that is unreliable, and of course
often is dependent on the time of the day.

Those frequencies are terribly reliable, interference aside.

Once that choice is made, then they have to live with the inefficiencey.
They have decided there is no other choice for their needs, and then
compensate with the high power to overcome the inefficiency of the
antennas.

As an example, there's a broadcast station in Ottawa on 580KHz that
comes in fine during the day. But at night, they are required to
cut back on their power, so the station goes away, not enough power
for ground wave to Montreal, while bouncing off the ionosphere
results in a bounce too far away. They have to cut back their power at
night so the better propagation at night does not leave them with
a booming signal bouncing off the ionosphere to interfere with all
the other stations on that frequency. I'm sure there are plenty of
locations much further away that can receive the station at night,
that can't receive it at night (after all, I can hear plenty of AM
broadcast stations at night from much further away that I could never
hear during the daytime). I did receive the Ottawa station at night
during one period a decade ago, when an emergency situation allowed
them to run full power at night; ground wave reception was fine.

So they run WWVB and such at low frequencies so the reliable ground
wave is used for really long distances (I can receive it fine here
in Montreal, I've had an "atomic clock" for almost five years and
rarely does it not sync up at night). One can argue that their
high power is not just because of the inefficient antennas at 60KHz,
but so it is receivable so far away, just like that Ottawa station
where the ground wave signal disappears when they lower their power.

WWVB and Loran-C use low frequencies for phase stability. Ionosphere
bounce has bad fading and erratic prop delay; ground wave is very
lossy but is much more amplitude and phase stable. Both are being
killed by GPS.

1000 watts is enough for SSB communications halfway around the world.
You can't do that with a megawatt of ELF.

John

 

[Michael Black]

On Sat, 26 Jul 2008, kronecker@yahoo.co.uk wrote:

On Jul 27, 4:05 am, j...@specsol.spam.sux.com wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
On Jul 26, 11:05 am, j...@specsol.spam.sux.com wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
On Jul 25, 12:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com
wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Thanks,

Radium
There is the modulation method - AM or FM. FM is more efficient - at
least narrowband FM. That's why we use FM for mobile transmitters. You
could use supressed-carrier AM of course but that is a sod to
demodulated.

Nonsense.

FM is common because it is intrinsically immune to impulse noise
and cheap to implement.

It's cheap but not immune to noise and suseptable to multipath big-
time.

I never said supressed carrier wasn't immune to noise.

As for multipath, all modulation methods are susceptable to it. FM has
a slight advantage there with discriminator capture.

Supressed carrier is trivial to demodulate these days but more
expensive to do.

Do tell how...It's not in any text book so maybe we can learn with
your advanced knowledge.

See any current amateur radio transceiver. There have been IC's to do
it for decades.

The higher the frequency the shorter the distance it can travel for a
given power. Therefore VLF can travel round the world and back again!

Nonsense.

Most long distance terrestrial communication is done on HF.

You have never heard of the inverse square law obviously. High
frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.

Define "high frequencies".

Things don't become line of sight until about 50 Mhz. Most long distance
terrestrial communications is done between about 5 Mhz and 30 Mhz, which
is HF.

The typical amateur radio transceiver puts out 100 W max in the HF
bands.

My log books, and the logs of 100s of thousands of amateur operators
are full of contacts around the globe with far less power than 100 W
in the 1.6 Mhz to 29 Mhz range.

No problem there.

trouble is you may need for ELF an aerial the size of a mountain
range!

About the only thing you got right.

The only thing we agree on - you must be a physicist - no idea about
engineering.

No, I'm a BSEE and an amateur radio operator for 40 years.

Have you ever seen a HF transmitter much less operated one?

As for your moon thing - it's line of site again!! Try communicating
from London to New York at 10GHz.

That's exactly the point. You can't communicate anywhere that isn't
line of sight much over about 100 Mhz no matter how much power you
run unless you use some reflective technique such as tropo scatter.

You know nothing about RF communications.

--
Jim Pennino

Remove .spam.sux to reply.

Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).
The only way (for analogue that is) is to recover the carrier and this
cannot be done since the carrier aint there in the first place!

Well there's a garbling, since it's far more common to see SSBsc, ie

Single Sideband with suppressed carrier. Either someone started with
a more complicated example for the sake of it, or it's suddenly
been reinforced to support a false notion.

A single sideband, and before going on this tangent the talk was of
ELF so if any voice modulation is going to go on down there it's going
to be SSBsc, is really easy to demodulate. Beat a signal against it,
and the sideband translates down to audio. No problem with mistuning,
you simply live with an odd sounding signal, a little retuning will
fix that.

Note that even if you started with a DSBsc signal, there are plenty
of SSB receivers out there perfectly capable of stripping off the unwanted
sideband and then the rest of the receiver treats it like it was an SSB
signal. Indeed, the only difference is that you wasted the power
used for the extra sideband. Sometimes that's fine, since it makes
the transmitter simpler.

But even if the discussion truly was DSBsc, demodulation is easy, and
has been well described for 50 years.

You don't look for the highly suppressed carrier, you get the information
about where to place the locally placed carrier at the receiver by
looking at the sidebands. Simple detectors of thirty years ago would
take the IF signal in the receiver, and double it in frequency, giving
a constant frequency, and divide it down by two to get the needed
frequency and it's right there in the middle, derived from the sidebands.

More complicated methods use a dual channel arrangement, with the VCO
locked to the outputs of the product detectors. Webb described a
practical circuit in CQ magazine about 1957 or 58, and while it used
a lot of tubes, it wasn't excessive. With solid state devices, it's
far easier.

A lot of portable shortwave receivers made in the past thirty years use
a synchronous detector, just what we are talking about, that work
just like that 1957 circuit.

Michael

 

On Jul 27, 4:05 am, j...@specsol.spam.sux.com wrote:

In sci.physics kronec...@yahoo.co.uk wrote:
On Jul 26, 11:05 am, j...@specsol.spam.sux.com wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
On Jul 25, 12:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com
wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

Thanks,

Radium
There is the modulation method - AM or FM. FM is more efficient - at
least narrowband FM. That's why we use FM for mobile transmitters. You
could use supressed-carrier AM of course but that is a sod to
demodulated.

Nonsense.

FM is common because it is intrinsically immune to impulse noise
and cheap to implement.

It's cheap but not immune to noise and suseptable to multipath big-
time.

I never said supressed carrier wasn't immune to noise.

As for multipath, all modulation methods are susceptable to it. FM has
a slight advantage there with discriminator capture.

Supressed carrier is trivial to demodulate these days but more
expensive to do.

Do tell how...It's not in any text book so maybe we can learn with
your advanced knowledge.

See any current amateur radio transceiver. There have been IC's to do
it for decades.

The higher the frequency the shorter the distance it can travel for a
given power. Therefore VLF can travel round the world and back again!

Nonsense.

Most long distance terrestrial communication is done on HF.

You have never heard of the inverse square law obviously. High
frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.

Define "high frequencies".

Things don't become line of sight until about 50 Mhz. Most long distance
terrestrial communications is done between about 5 Mhz and 30 Mhz, which
is HF.

The typical amateur radio transceiver puts out 100 W max in the HF
bands.

My log books, and the logs of 100s of thousands of amateur operators
are full of contacts around the globe with far less power than 100 W
in the 1.6 Mhz to 29 Mhz range.

No problem there.

trouble is you may need for ELF an aerial the size of a mountain
range!

About the only thing you got right.

The only thing we agree on - you must be a physicist - no idea about
engineering.

No, I'm a BSEE and an amateur radio operator for 40 years.

Have you ever seen a HF transmitter much less operated one?

As for your moon thing - it's line of site again!! Try communicating
from London to New York at 10GHz.

That's exactly the point. You can't communicate anywhere that isn't
line of sight much over about 100 Mhz no matter how much power you
run unless you use some reflective technique such as tropo scatter.

You know nothing about RF communications.

--
Jim Pennino

Remove .spam.sux to reply.

Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).
The only way (for analogue that is) is to recover the carrier and this
cannot be done since the carrier aint there in the first place!

Try locking a PLL into supressed carrier. So you are talking complete
rubbish.

Here is the basic euqation

m.cos(wmt)cos(wct) where wm and wc are the modulating and carrier
frequencies and m is the amplitude. Actually what you are probably
thinking of is where a BFO is multiplied into this. However this is
not stable and not phase-locked to the carrier either.It needs
constant adjustment though its a lot better than it was because of DDS
and stable crystals that we didn't have a long time back. If you try
and limit the signal to recover the carrier then it will work at high
SNRs but not at low SNRs.

K.

 

[Michael Black]

On Sat, 26 Jul 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics kronecker@yahoo.co.uk wrote:



Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).

Nonsense but irrelevant as virtually no one uses double side band
supressed carrier and it has nothing whatsoever to do with the previous
discussion.

Double side band was played with about 40 years ago and essentially
abandoned as ssb is more efficient both in bandwidth and power.

Most all supressed carrier is done single side band.

Vestigial sideband is used extensively as in analog TV broadcast.

Though oddly enough, the problem with SSB is that it's hard to tune.

Not in terms of receiving something listenable to, but to tune it
exactly. There is nothing to lock onto, so one always has to make
do with "that's about right". It's fine for voice since mistuning
only makes someone sound higher or lower pitched. But music is
horrible since you do notice when it's mistuned.

The redundant sideband, as I posted about earlier, allows for
perfect tuning of the reinserted carrier. Plus the redundant
sideband, with the right detector, allows for a certain level
of frequency diversity reception, and of course the redundancy
means one sideband may arrive at your receiver without interference
while you have to live with what you get if one sideband is
sent.

The carrier is the main hog of power at the transmitter, eliminate
it and you get a far bigger level of efficiency than going whole
hog and getting rid of the extra sideband. Sending the extra
sideband gives those advantages.

Michael

 

[Don Bowey]

On 7/26/08 5:15 PM, in article hoqsl5-mre.ln1@mail.specsol.com,
"jimp@specsol.spam.sux.com" <jimp@specsol.spam.sux.com> wrote:

In sci.physics Michael Black <et472@ncf.ca> wrote:
On Sat, 26 Jul 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics kronecker@yahoo.co.uk wrote:



Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).

Nonsense but irrelevant as virtually no one uses double side band
supressed carrier and it has nothing whatsoever to do with the previous
discussion.

Double side band was played with about 40 years ago and essentially
abandoned as ssb is more efficient both in bandwidth and power.

Most all supressed carrier is done single side band.

Vestigial sideband is used extensively as in analog TV broadcast.

Though oddly enough, the problem with SSB is that it's hard to tune.
Not in terms of receiving something listenable to, but to tune it
exactly. There is nothing to lock onto, so one always has to make
do with "that's about right". It's fine for voice since mistuning
only makes someone sound higher or lower pitched. But music is
horrible since you do notice when it's mistuned.

Why would anyone in their right mind transmit music with SSB?

Because they could, economically. Before the conversion to digital
transmission, telecoms transmitted 20kHz audio via SSB coast-to-coast.

Music is generally about fidelity which means bandwidth.

Yes, but that doesn't preclude ssb when you know how to do it well.

One of the primary reasons for using SSB is to reduce bandwidth.

The redundant sideband, as I posted about earlier, allows for
perfect tuning of the reinserted carrier. Plus the redundant
sideband, with the right detector, allows for a certain level
of frequency diversity reception, and of course the redundancy
means one sideband may arrive at your receiver without interference
while you have to live with what you get if one sideband is
sent.

I doubt you are going to see much benefit from a frequency diversity
of 6 Khz at 10 Mhz.

The carrier is the main hog of power at the transmitter, eliminate
it and you get a far bigger level of efficiency than going whole
hog and getting rid of the extra sideband. Sending the extra
sideband gives those advantages.

Well, it all depends on what it is you are trying to achieve.

 

[cliff wright]

jimp@specsol.spam.sux.com wrote:

In sci.physics Michael Black <et472@ncf.ca> wrote:

On Sat, 26 Jul 2008, jimp@specsol.spam.sux.com wrote:


In sci.physics kronecker@yahoo.co.uk wrote:




Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).

Nonsense but irrelevant as virtually no one uses double side band
supressed carrier and it has nothing whatsoever to do with the previous
discussion.

Double side band was played with about 40 years ago and essentially
abandoned as ssb is more efficient both in bandwidth and power.

Most all supressed carrier is done single side band.

Vestigial sideband is used extensively as in analog TV broadcast.


Though oddly enough, the problem with SSB is that it's hard to tune.
Not in terms of receiving something listenable to, but to tune it
exactly. There is nothing to lock onto, so one always has to make
do with "that's about right". It's fine for voice since mistuning
only makes someone sound higher or lower pitched. But music is
horrible since you do notice when it's mistuned.


Why would anyone in their right mind transmit music with SSB?

Music is generally about fidelity which means bandwidth.

One of the primary reasons for using SSB is to reduce bandwidth.


The redundant sideband, as I posted about earlier, allows for
perfect tuning of the reinserted carrier. Plus the redundant
sideband, with the right detector, allows for a certain level
of frequency diversity reception, and of course the redundancy
means one sideband may arrive at your receiver without interference
while you have to live with what you get if one sideband is
sent.


I doubt you are going to see much benefit from a frequency diversity
of 6 Khz at 10 Mhz.


The carrier is the main hog of power at the transmitter, eliminate
it and you get a far bigger level of efficiency than going whole
hog and getting rid of the extra sideband. Sending the extra
sideband gives those advantages.


Well, it all depends on what it is you are trying to achieve.

Stone me! What a mess we can get into sometimes here.

Lets point out a few facts about VLF signals (below say 50KHz).
1. Yes indeed. You need a "dirty great" antenna. These frequencies have
been used since almost the beginning of radio and antenna designs of
enormous proportions have gone with them.
In 1907/8 Marconi used 45KHz for transatlantic service from Ireland
and used an antenna about 3Km long by 1Km wide with about 50 Kw of
rotary gap spark power. Later the German staion at Nauen used directly
generated 24 KHz and an antenna like a vast skeletal circus tent 200 m
high at the centre and 75 m high at the edges covering many hectares of
ground.
This could be recieved by a crystal set in South America.
Megawatts while common to overcome antenna losses are mainly used to
make the service as absolutely reliable as possible.
Also early means of generation like arc transmitters tended to be
easy to build in high power forms. Like the US navy's 0.5MW staions
built about the end of WW1, and the arc system was inherently limited to
low frequencies.
The signal is apparently ducted between the ground and lower ionospher
which explains the world wide coverage.
ALL these signals have to be low speed telegraphy of some kind. The
bandwidth of the tuned antennas alone would preclude the use of
modulated signals, and ther simply isn't the spectrum space for
sidebands in their usual sense.
The lowest frequency I have ever come across, and I have had a
professional and amateur interest in it for many years is 9KHz
although in practice around 12 KHz is getting near the practical limit.
It is of course simply VERY much easier to radiate higher frequencies.
As soon as Hams discovered the properties of short waves in the early
1920's most of this ELF disappeared except for specialist applications
like submarine communication. BTW I've always wondered what sort of
antenna the sub uses for reception? I bet that's still classified perhaps?
Cliff Wright ZL1BDA ex G3NIA

 

[Michael Black]

On Sun, 27 Jul 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics Michael Black <et472@ncf.ca> wrote:
On Sat, 26 Jul 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics kronecker@yahoo.co.uk wrote:



Amateurs are the worst kind! There is not way to demodulate double
side-band supressed carrier (esp at low SNRs).

Nonsense but irrelevant as virtually no one uses double side band
supressed carrier and it has nothing whatsoever to do with the previous
discussion.

Double side band was played with about 40 years ago and essentially
abandoned as ssb is more efficient both in bandwidth and power.

Most all supressed carrier is done single side band.

Vestigial sideband is used extensively as in analog TV broadcast.

Though oddly enough, the problem with SSB is that it's hard to tune.
Not in terms of receiving something listenable to, but to tune it
exactly. There is nothing to lock onto, so one always has to make
do with "that's about right". It's fine for voice since mistuning
only makes someone sound higher or lower pitched. But music is
horrible since you do notice when it's mistuned.

Why would anyone in their right mind transmit music with SSB?

Your efficiency, both in terms of power and in terms of spectrum

utilization. You only need one sideband for content, so why send
the extra sideband (redundancy aside). Almost forty years ago,
shortwave broadcast stations did start talking about and/or playing
with SSB, to make better use of their allocated spectrum. Shortwave
broadcast stations transmit music as part of their programming.

Music is generally about fidelity which means bandwidth.

One of the primary reasons for using SSB is to reduce bandwidth.

Which you get when you drop the other sideband, and instant halving

of the bandwidth used.

There is nothing inherently narrow bandwidth about SSB. It does
tend to be narrow because you are mostly transmitting only voice,
and that doesn't take up much bandwidth. And it was certainly
easier to restrict bandwdith with SSB, since in the early days
those phasing methods were so limited that they couldn't deal
with wide bandwidth, and it's easier to make a crystal filter
that is narrow than wide.

So long as only voice was used for SSB, nobody gave this thought.
But once shortwave broadcasters started to play with SSB, then
of course they had to reveal that SSB could indeed be wide bandwidth
(yet still narrower than an equivalent DSB signal, since the
extra sideband is never sent).

The redundant sideband, as I posted about earlier, allows for
perfect tuning of the reinserted carrier. Plus the redundant
sideband, with the right detector, allows for a certain level
of frequency diversity reception, and of course the redundancy
means one sideband may arrive at your receiver without interference
while you have to live with what you get if one sideband is
sent.

I doubt you are going to see much benefit from a frequency diversity
of 6 Khz at 10 Mhz.

But that is precisely what causes a lot of problems with AM with full

carrier over long distances. The sideband(s) arrive while the carrier
fades, and then there's not enough carrier to properly demodulate
it. You have to reinsert the carrier at the receiver, so all
those synchronous detectors have determined where to place it by
using the sidebands as the information.

This isn't a guess, DSB when demodulated properly is seen as a diversity
method. Obviously not as good as transmitting on two very distinct
frequencies, but it's there, and a lot simpler than having two
transmitters.

Michael

 

[Michael Black]

On Sun, 27 Jul 2008, christofire wrote:

"cliff wright" <c.c.wright@paradise.net.nz> wrote in message
news:488c699f$1@clear.net.nz...
jimp@specsol.spam.sux.com wrote:

In sci.physics Michael Black <et472@ncf.ca> wrote:

On Sat, 26 Jul 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics kronecker@yahoo.co.uk wrote:

Amateurs are the worst kind! etc.

Stone me! What a mess we can get into sometimes here.
Lets point out a few facts about VLF signals (below say 50KHz).
1. Yes indeed. You need a "dirty great" antenna. These frequencies have
been used since almost the beginning of radio and antenna designs of
enormous proportions have gone with them.
In 1907/8 Marconi used 45KHz for transatlantic service from Ireland
and used an antenna about 3Km long by 1Km wide with about 50 Kw of rotary
gap spark power. Later the German staion at Nauen used directly generated
24 KHz and an antenna like a vast skeletal circus tent 200 m high at the
centre and 75 m high at the edges covering many hectares of ground.
This could be recieved by a crystal set in South America.
Megawatts while common to overcome antenna losses are mainly used to make
the service as absolutely reliable as possible.
Also early means of generation like arc transmitters tended to be
easy to build in high power forms. Like the US navy's 0.5MW staions built
about the end of WW1, and the arc system was inherently limited to low
frequencies.
The signal is apparently ducted between the ground and lower ionospher
which explains the world wide coverage.
ALL these signals have to be low speed telegraphy of some kind. The
bandwidth of the tuned antennas alone would preclude the use of modulated
signals, and ther simply isn't the spectrum space for sidebands in their
usual sense.
The lowest frequency I have ever come across, and I have had a
professional and amateur interest in it for many years is 9KHz
although in practice around 12 KHz is getting near the practical limit.
It is of course simply VERY much easier to radiate higher frequencies.
As soon as Hams discovered the properties of short waves in the early
1920's most of this ELF disappeared except for specialist applications
like submarine communication. BTW I've always wondered what sort of
antenna the sub uses for reception? I bet that's still classified perhaps?
Cliff Wright ZL1BDA ex G3NIA


Take a look at the RN Radar and Radio Museum pages at
http://www.rnmuseumradarandcommunications2006.org.uk/PAGE%2032.htm. There's
some information on a variety of different types of LF/VLF receiving
antenna, the ALK for example, which apparently used loops attached to a
buoy. Lots of reference to the 10 to 40 kHz frequency range here. Also it
seems fairly well known that transmission of VLF signals to UK submarines
was moved from BT's Rugby station to VTC's Anthorn station
http://tx.mb21.co.uk/gallery/anthorn.php in 2003 or thereabouts. The
frequency of these transmissions seems to be variously reported as 16 kHz,
19.6 kHz, etc. - perhaps it's FSK.

I seem to recall reading that submarines did generally come close to the

surface to receive signals, so I think the buoy system makes sense. And
of course, a lot of work has been done on making good receiving antennas
at low frequencies, loops and even active elements. You lose too much
trying to use a tiny antenna to transmit low frequencies, so you have
to keep raising the power and at some point you get virtually no return
for the increases. At the receiver, you use amplification to compensate,
but it's easier to amplify small signals than power signals.

Incidentally, the remark above 'the arc system was inherently limited to low
frequencies' is probably incorrect. The arc was just a means of making and
breaking a circuit and history records that some of the earliest
demonstrations of radio (Lodge and others) were carried out in lecture
theatres using a sparking induction coil and a short dipole antenna (two
plates) transmitting to a nearby loop antenna. The average wavelength may
have been around a metre or less.

Spark seems to be what you are talking about, and yes it was inherently

wideband.

The arc transmitter came a bit later, and was limited to relatively
low freuqencies (though I'm not sure the limitation was noticed
at the time; as previously posted for a while the higher frequencies
were dismissed as "useless" so everyone hung around a relatively
small slice of the spectrum). It was a real CW transmitter, the arc
transmitter was a real oscillator.

I seem to recall there were also transmitters that used mechanical
generators to cause a CW signal, and those obviously were limited
to low frequencies.

Michael