You would think they would run at least 1,000,000 watts at 60khz to get better range.
That would be more than +12db from what they run now and would make a big difference.
They waste money on everything else so why not make the time signals more usable.
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- Some mornings I wake up cranky.....but usually I just let him sleep -
You can by alarm clocks, for about $10, around here that sync to DCF77.
I bought one last year, it only worked for two days so I exchanged it. The next one worked for a week. At that point a got tired of running back to the shop so I cracked it open.
The antenna is only an old trany radio style coil on ferrite rod about 4cm long. To tune it up there is cheapo capacitor soldered across it.
Amazing it received anything.
So there's the antenna for my Prop DCF77 receiver.
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For me, the past is not over yet.
The most power I put into an aerial was 500KW (real Watts). This used two 250KW sets paralleled up and stuck up an experimental multi-band array (500 ft masts). The array took it ok, but the old farm house right in front of it suffered "internal lightning". Good old days.
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Style and grace : Nil point
The WWVB antenna.
I see wires from tower top to tower top.
That antenna looks awfully close to the ground for 60khz.
Maybe about like supporting a 10 meter dipole from
pencils stuck in the ground. Then again, if there were
any frackin sunspots you could probably work China
on a 10 meter dipole that close to the ground
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- Some mornings I wake up cranky.....but usually I just let him sleep -
Post Edited (HollyMinkowski) : 9/3/2009 8:14:24 AM GMT
According their web site DCF77 has main and standby antennas of 150m and 200m height respectively.
The tallest antenna mast in the world is KVLY-TV at 629m so they are not doing so badly.
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For me, the past is not over yet.
Back in the 70's there were articals in WW about 10KHz aerials, slung across Swiss mountain tops. Submarine comms probably. There is an escarpment to high masts setup in Shropshire, UK (not on the map).
Holly·· The fact that the land under your topband aerial is sandy will help it. The effective ground will be lower than the real gound level, which is the same as the aerial being·higher up (assuming that the sand isn't full of salt water)
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Style and grace : Nil point
Slightly off-topic note - I used to have an Icom R-70A HF receiver.· It literally tunes all the way down to zero Hz, but I was convinced anything below 150 KHz was probably unusable due to analog circuit constraints.· That is, until I successfully received WWVB at 60 KHz.· This was in Los Angeles, and with an indoor wire antenna and poor ground.
WWVB·uses a weird modulation - it's not meant to hear by ear.· To do so, you need to tune slightly off frequency and use either the CW or USB mode.· But it was there all right.· I listened to the signal a long time (I was quite happy at that "catch"), and it followed the pattern documented by NIST.
There is no voice signal of course - it carries a binary signal pattern.· WWV/WWVH, while carrying voice signals, also have a binary·signal as well.· On those stations, listen sometime for the low-frequency pulses - you can make them out by ear, and decode them using the pattern guide from NIST.
I always wondered if that was so about the sandy soil.
Since dirt is somewhat conductive I wonder how far
you could communicate by sending current pulses
through the ground?
If you drove 2 copper ground rods into the soil
and separated them by say 1000' and sent strong
DC pulses through that circuit just how far away
could you be with a detector of some sort and still detect
that current flow?
If you sent really massive pulses it might be a long
way. Like if you charged up high v capacitors and
discharged them through the earth between the rods.
Wouldn't it be somewhat like rf as far as propagation goes? I mean
the signal would drop off dramatically but no matter how
weak they became wouldn't they still exist many miles away?
Wouldn't every possible path between the 2 rods be
a resistor that would always carry at least some tiny fraction
of the electron flow? Even if that path traveled from one pole
to a point a hundred miles away and then back, there would
have to be some small number of electrons following that
path...it seems so?
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- Some mornings I wake up cranky.....but usually I just let him sleep -
It would be like any other sheet resistance. Take a square of carbon impregnated cloth and plunk down two electrodes at opposite ends of the square, in a little bit from the edges, and run pulses of electricity between the electrodes and measure the voltages between points on the cloth. You can simulate this pretty easily on a computer with a nice graph of the voltage detected. If you used an AC waveform to excite it, you'd even get radiated RF. Most of the energy would go into heating up the sheet resistance (or ground), but some of it would radiate.
I just love thinking about how far signals can propagate.
Like how you can calculate the size dish you would need
to detect a .01 watt microwave signal sent from Alpha Centari using a simple
1/4 wave whip antenna. The dish would be huge but if you
built it you would be able to copy the signal after it had
made the 4 year trip to earth
Doubling the size of a dish gives you a 3db boost in signal.
A dish the size of a Direct TV dish has about 26db of gain.
The huge Robert C. Byrd dish at Green Bank has a bit over 80db
and one that could pick up that weak signal from 4 light years out
would probably need something approaching 100db (I have not
done the calcs) and the dish would really be something to look at,
it would be so big you would have to construct it in a gravity free
location because gravity stresses would tear it apart...I guess the
only place would be the spot between earth and moon where the
gravity balances to zero value. Some day such projects will
be carried out by robots, humans could never see such jobs through.
The light frequency radiation from a single LED travels easily
all the way to a distant place like mars. It seems unbelievable
but if you just think about it a little. Like if the earth was in darkness
you could not see it with an instrument from mars but if you then
covered the whole earth with glowing LEDs it is obvious you
could see that from mars, so that means that the light from every
LED makes it there, albeit only a few photons from each one.
Thought experiments, I just love em
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- Some mornings I wake up cranky.....but usually I just let him sleep -
The Byrd dish at Green Bank, note that
it is an offset feed dish same as the little dishes
you see on homes everywhere, except grown very large.
EDIT: The reason the feed is at the top of the dish and not
at the easier to engineer bottom location like a home satellite
dish is because that allows the dish to point at the horizon. If the feed
was at the bottom then to see the horizon the dish would have to be elevated
on a pedestal so you could tilt it down far enough...and it would look
pretty silly
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Post Edited (HollyMinkowski) : 9/3/2009 7:04:45 PM GMT
A friend and me used to talk though the ground back, when we were at school. We were about half a mile away from each other and put about 30Volts p/p into each end. My parents garden was end on to his direction but his was completely side on and so he could get about 150 ft separation to my 30 ft. It was never solid and full of all sorts of interference. One pole and the mains earth was much better.
Kept us off the streets, I suppose.
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Style and grace : Nil point
The fact that you were able to do that has to mean that
data could be passed between distant points without
wires and without rf or light.
Now how could we do this with 2 props???
The cheapest possible way of course, I'm very frugal
I'm guessing that the data rate would have to be low and
that a lot of error correction might be needed and involve
quite a bit of re-transmission, maybe 56kbps at a few miles
would be a possibility?
It would be fun to make 2 simple prop devices that
could deliver phone modem speed internet to someone
a few miles away! I know it's a simple thing to send
wifi from a cheap router that far but this would involve no
telltale antennas
What a fun idea.
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- Some mornings I wake up cranky.....but usually I just let him sleep -
I don't think your "low" speed of 56K would be posible. We were only messing about with audio so I bet 300/1200 Baud would be nearer the mark.
There is a 1200 Baud objet already.
As for your upside down dish. I turned my fathers dish that way so that it didnt get such a bashing from the gales. Where he lives on the south coast, there is a strait line to South America for the wind to work up some enthusiasm.
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Style and grace : Nil point
Post Edited (Toby Seckshund) : 9/3/2009 7:16:48 PM GMT
What is the possibility of increasing the range using fractal antennas which is what a lot of cell phones use?
I was watching a program on PBS and some·man got the idea to make fractal antennas out of learning about Mandelbrots because he was getting in trouble with his landlord who didn't allow antennas on·his balcony and·fractal antennas·helped make some cell phones possible.
"Although the first validation of the technology was published as early as 1995 (see ref.1) recent independent studies continue to show the superiority of the fractal element technology in real-life applications, such as RFID.[noparse][[/noparse]4]"
Fractal type aerials were around before 95 but they probably didn't get around to grabbing the name rights. Early (UK) Sat ae's were flat and small but that company got swamped by the evil one and the bright white dishes sprouted.
To try and get around the ravages of the wind my father and me made a "Blind aerial" from concenteric foil rings on a window roller blind (scaled fron the SETI site). LMB in the right place and pull down the blind an there was the signal. Working out the elipses for 30 degree ele and 18 deg E/W offset was a bit mind blowing. In the end it was done with a wall, tracing paper and an overhead projector.
We made 'us own entertainment.
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Style and grace : Nil point
I turned the small dish I rigged up for wifi upside down
like that as I could not aim at the horizon with it on the bottom.
The pole did not allow it to be positioned low enough...
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[noparse][[/noparse]quote] I don't think your "low" speed of 56K would be posible. We were only messing about with audio so I bet 300/1200 Baud would be nearer the mark.
There is a 1200 Baud objet already.
EDIT: (quote, malfunctioned ^^^)
The frequencies that 56K telephone modems used are actually in the range of 300-3000 Hz.
It took me awhile to find someone who could tell me how that worked at the time because
you can't modulate 56000 pulses on a channel that only allows 3000 pulses, but it uses
phase modulation, either Quadrature AM (sine+cosine dual carrier on same frequency)
or Quadrature Phase Shift Modulation (quickly selecting different pieces of the sine and cosine
maybe 4 times AT LEAST within one cycle of the carrier frequency). It's simpler to use 300 or 1200,
or DTMF, or Teletype, or Kansas City Standard/ BYTE Standard or even high speed morse code.
FCC in Region 2 does not regulate that telephone audio "Voice Frequency" band, so turn on your loud hi-fi
with the BASS up and the TREBLE down, and the volume up to ELEVEN (haha), and then
connect it to two different grounds for simplex (not simultaneous) transmitting and receiving.
If you get the buzz from power line radiation then use a delay or notch filter to cancel it out.
If you receive very high pitched data noises that way, it means the sky is falling! 8O
The 56K modem spec also relies on the fact that beyond the (short) local loop, everything is digital, and it only works at that speed if it's digital all the rest of the way to the server (e.g. via a T1 line or better). If communicating phone to phone (i.e. analog loop -> digital -> analog loop), you will not get 56Kbaud.
Phil, please clarify. I could see that maybe communicating data at 56K in an audio analog line may only work for short distances. But I don't see if my short analog connection to a digital network works at 56K at my end why it can'y work just the same at, say your, end.
Anyway doesn't 56K rely on compression? I always though that was cheating.
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For me, the past is not over yet.
Heater, your so called 56K modem is asymmetrical device when working in that mode (RX@56K, TX@33K). When you are connected to your ISP you have 1 A/D conversion from your line to the telephone company equipment. From here the data are routed/exchanged digitally to/with your ISP. When connecting to a friend your data have 1 A/D conversion from line to telephone central equipment, than they are routed digitally to the destination and converted again (D/A) before entering into your friend's line. So you have double conversion which introduce to much errors in the communication. This is one point, the second is that your modem is asymmetrical so your RX@56K is coming from your friend's TX@33K and vice-versa.
The telephone copper line bandwitdth should not be a problem, if you think on ADSL speeds, but again here you have only one A/D conversion between your ADSL modem and ISP's DSLAM.
dMajo. I forgot about the asymmetry. That's another "cheat" to make the spec look good in my mind.
Also what I forgot is that the analog signal from my modem gets converted to a digital voice stream for transport over the telephone network. At that point it must be severely bandwidth limited. Even if the short twisted pair copper out of my house to the exchange can handle the speed that digital voice channel from then on probably does not.
In my last job my company had designed its own DSL routers 3 ports per box working at 2MB/sec over 3Km or more. so the copper should not be the problem.
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For me, the past is not over yet.
Copper to copper took all those years of·improvements and "cheats". When you are sticking a couple of copper pipes into the ground... It would be interesting to see·what the·group delay characteristics of an open field (with and without a cow) would·give.
As Holly is a Lady, She may not be willing to water them in properly.
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Style and grace : Nil point
I know you are frugal but I found this new product which has a 40 mile range on Sparkfun and it isn't cheap but you have to be able to do at least 9600 or 115,200 bps.· Here is the link:
Heater: Modems over the switched network (PSTN) are limited to 4KHz bandwidth at the telephone exchange as they are then packed up into blocks. The 56Kbps is the actual speed although this is often not achieved due to line conditions between the house and telephone exchange. Compression is on top of this. However, there is redundency within the 56Kbps. I am not sure of the actual method in 56K but in lower speeds, QAM (Quadrature ??? Modulation) was used where 4 bits (probably more later) were sent simultaneously depicting a quadrant where the signal was. Phase shifting and other methods were used.
There was a modem called TrailBlazer which used a totally different technique which used multiple sections of the 4KHz bandwith. I think they split it into 7Hz channels and sent each channel slowly (300baud?). It provided about 500 channels and they selected the best group from this. From memory, it used a TMS320 DSP to do this. It was a half duplex system with a tiny back channel.
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Aerial farms like that were the norm in the 60's for overseas telecommunications before undersea cables and satellites.
Then came the huge satellite dishes with cryogenic cooling on the back of the dish for the LNA's (low noise receivers) which is when they discovered microwaves cooked the birds flying in front of them. A few years later they had improved the receivers enough that the receivers could be in a building and refrigeration was no longer required. I saw both at OTC (the phone company) at Ceduna, South Australia in 1971 on one of my training trips. Absolutely fascinating.
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Comments
You would think they would run at least 1,000,000 watts at 60khz to get better range.
That would be more than +12db from what they run now and would make a big difference.
They waste money on everything else so why not make the time signals more usable.
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- Some mornings I wake up cranky.....but usually I just let him sleep -
I bought one last year, it only worked for two days so I exchanged it. The next one worked for a week. At that point a got tired of running back to the shop so I cracked it open.
The antenna is only an old trany radio style coil on ferrite rod about 4cm long. To tune it up there is cheapo capacitor soldered across it.
Amazing it received anything.
So there's the antenna for my Prop DCF77 receiver.
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For me, the past is not over yet.
Maybe you could wind a few hundred feet of wire onto a 10' piece of PVC pipe
and then mount it outside for an antenna.
Reception would be great and your wife would love it.
LoL
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Style and grace : Nil point
I see wires from tower top to tower top.
That antenna looks awfully close to the ground for 60khz.
Maybe about like supporting a 10 meter dipole from
pencils stuck in the ground. Then again, if there were
any frackin sunspots you could probably work China
on a 10 meter dipole that close to the ground
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- Some mornings I wake up cranky.....but usually I just let him sleep -
Post Edited (HollyMinkowski) : 9/3/2009 8:14:24 AM GMT
The tallest antenna mast in the world is KVLY-TV at 629m so they are not doing so badly.
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For me, the past is not over yet.
Holly·· The fact that the land under your topband aerial is sandy will help it. The effective ground will be lower than the real gound level, which is the same as the aerial being·higher up (assuming that the sand isn't full of salt water)
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Style and grace : Nil point
WWVB·uses a weird modulation - it's not meant to hear by ear.· To do so, you need to tune slightly off frequency and use either the CW or USB mode.· But it was there all right.· I listened to the signal a long time (I was quite happy at that "catch"), and it followed the pattern documented by NIST.
There is no voice signal of course - it carries a binary signal pattern.· WWV/WWVH, while carrying voice signals, also have a binary·signal as well.· On those stations, listen sometime for the low-frequency pulses - you can make them out by ear, and decode them using the pattern guide from NIST.
- Earl
I always wondered if that was so about the sandy soil.
Since dirt is somewhat conductive I wonder how far
you could communicate by sending current pulses
through the ground?
If you drove 2 copper ground rods into the soil
and separated them by say 1000' and sent strong
DC pulses through that circuit just how far away
could you be with a detector of some sort and still detect
that current flow?
If you sent really massive pulses it might be a long
way. Like if you charged up high v capacitors and
discharged them through the earth between the rods.
Wouldn't it be somewhat like rf as far as propagation goes? I mean
the signal would drop off dramatically but no matter how
weak they became wouldn't they still exist many miles away?
Wouldn't every possible path between the 2 rods be
a resistor that would always carry at least some tiny fraction
of the electron flow? Even if that path traveled from one pole
to a point a hundred miles away and then back, there would
have to be some small number of electrons following that
path...it seems so?
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- Some mornings I wake up cranky.....but usually I just let him sleep -
I just love thinking about how far signals can propagate.
Like how you can calculate the size dish you would need
to detect a .01 watt microwave signal sent from Alpha Centari using a simple
1/4 wave whip antenna. The dish would be huge but if you
built it you would be able to copy the signal after it had
made the 4 year trip to earth
Doubling the size of a dish gives you a 3db boost in signal.
A dish the size of a Direct TV dish has about 26db of gain.
The huge Robert C. Byrd dish at Green Bank has a bit over 80db
and one that could pick up that weak signal from 4 light years out
would probably need something approaching 100db (I have not
done the calcs) and the dish would really be something to look at,
it would be so big you would have to construct it in a gravity free
location because gravity stresses would tear it apart...I guess the
only place would be the spot between earth and moon where the
gravity balances to zero value. Some day such projects will
be carried out by robots, humans could never see such jobs through.
The light frequency radiation from a single LED travels easily
all the way to a distant place like mars. It seems unbelievable
but if you just think about it a little. Like if the earth was in darkness
you could not see it with an instrument from mars but if you then
covered the whole earth with glowing LEDs it is obvious you
could see that from mars, so that means that the light from every
LED makes it there, albeit only a few photons from each one.
Thought experiments, I just love em
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- Some mornings I wake up cranky.....but usually I just let him sleep -
it is an offset feed dish same as the little dishes
you see on homes everywhere, except grown very large.
EDIT: The reason the feed is at the top of the dish and not
at the easier to engineer bottom location like a home satellite
dish is because that allows the dish to point at the horizon. If the feed
was at the bottom then to see the horizon the dish would have to be elevated
on a pedestal so you could tilt it down far enough...and it would look
pretty silly
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Post Edited (HollyMinkowski) : 9/3/2009 7:04:45 PM GMT
Kept us off the streets, I suppose.
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Style and grace : Nil point
That is just amazing!!
The fact that you were able to do that has to mean that
data could be passed between distant points without
wires and without rf or light.
Now how could we do this with 2 props???
The cheapest possible way of course, I'm very frugal
I'm guessing that the data rate would have to be low and
that a lot of error correction might be needed and involve
quite a bit of re-transmission, maybe 56kbps at a few miles
would be a possibility?
It would be fun to make 2 simple prop devices that
could deliver phone modem speed internet to someone
a few miles away! I know it's a simple thing to send
wifi from a cheap router that far but this would involve no
telltale antennas
What a fun idea.
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- Some mornings I wake up cranky.....but usually I just let him sleep -
I don't think your "low" speed of 56K would be posible. We were only messing about with audio so I bet 300/1200 Baud would be nearer the mark.
There is a 1200 Baud objet already.
As for your upside down dish. I turned my fathers dish that way so that it didnt get such a bashing from the gales. Where he lives on the south coast, there is a strait line to South America for the wind to work up some enthusiasm.
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Style and grace : Nil point
Post Edited (Toby Seckshund) : 9/3/2009 7:16:48 PM GMT
I was watching a program on PBS and some·man got the idea to make fractal antennas out of learning about Mandelbrots because he was getting in trouble with his landlord who didn't allow antennas on·his balcony and·fractal antennas·helped make some cell phones possible.
"Although the first validation of the technology was published as early as 1995 (see ref.1) recent independent studies continue to show the superiority of the fractal element technology in real-life applications, such as RFID.[noparse][[/noparse]4]"
http://en.wikipedia.org/wiki/Fractal_antenna
Fractal type aerials were around before 95 but they probably didn't get around to grabbing the name rights. Early (UK) Sat ae's were flat and small but that company got swamped by the evil one and the bright white dishes sprouted.
To try and get around the ravages of the wind my father and me made a "Blind aerial" from concenteric foil rings on a window roller blind (scaled fron the SETI site). LMB in the right place and pull down the blind an there was the signal. Working out the elipses for 30 degree ele and 18 deg E/W offset was a bit mind blowing. In the end it was done with a wall, tracing paper and an overhead projector.
We made 'us own entertainment.
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Style and grace : Nil point
I turned the small dish I rigged up for wifi upside down
like that as I could not aim at the horizon with it on the bottom.
The pole did not allow it to be positioned low enough...
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Does Switzerland have a navy, let alone submarines?
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
communications to submarine fleets.
The Swiss are so trustworthy with secrets...NOT!
(google UBS accounts tax)
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- Some mornings I wake up cranky.....but usually I just let him sleep -
There is a 1200 Baud objet already.
EDIT: (quote, malfunctioned ^^^)
The frequencies that 56K telephone modems used are actually in the range of 300-3000 Hz.
It took me awhile to find someone who could tell me how that worked at the time because
you can't modulate 56000 pulses on a channel that only allows 3000 pulses, but it uses
phase modulation, either Quadrature AM (sine+cosine dual carrier on same frequency)
or Quadrature Phase Shift Modulation (quickly selecting different pieces of the sine and cosine
maybe 4 times AT LEAST within one cycle of the carrier frequency). It's simpler to use 300 or 1200,
or DTMF, or Teletype, or Kansas City Standard/ BYTE Standard or even high speed morse code.
FCC in Region 2 does not regulate that telephone audio "Voice Frequency" band, so turn on your loud hi-fi
with the BASS up and the TREBLE down, and the volume up to ELEVEN (haha), and then
connect it to two different grounds for simplex (not simultaneous) transmitting and receiving.
If you get the buzz from power line radiation then use a delay or notch filter to cancel it out.
If you receive very high pitched data noises that way, it means the sky is falling! 8O
Post Edited (VIRAND) : 9/4/2009 5:26:36 AM GMT
-Phil
Anyway doesn't 56K rely on compression? I always though that was cheating.
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For me, the past is not over yet.
Everything I know I learned from Wikipedia: en.wikipedia.org/wiki/56_kbit/s_modem.
-Phil
The telephone copper line bandwitdth should not be a problem, if you think on ADSL speeds, but again here you have only one A/D conversion between your ADSL modem and ISP's DSLAM.
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· Propeller Object Exchange (last Publications / Updates)
Also what I forgot is that the analog signal from my modem gets converted to a digital voice stream for transport over the telephone network. At that point it must be severely bandwidth limited. Even if the short twisted pair copper out of my house to the exchange can handle the speed that digital voice channel from then on probably does not.
In my last job my company had designed its own DSL routers 3 ports per box working at 2MB/sec over 3Km or more. so the copper should not be the problem.
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For me, the past is not over yet.
As Holly is a Lady, She may not be willing to water them in properly.
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Style and grace : Nil point
I know you are frugal but I found this new product which has a 40 mile range on Sparkfun and it isn't cheap but you have to be able to do at least 9600 or 115,200 bps.· Here is the link:
XTend 900 1W RPSMA - 40 Mile Range
sku: WRL-09411
·
There was a modem called TrailBlazer which used a totally different technique which used multiple sections of the 4KHz bandwith. I think they split it into 7Hz channels and sent each channel slowly (300baud?). It provided about 500 channels and they selected the best group from this. From memory, it used a TMS320 DSP to do this. It was a half duplex system with a tiny back channel.
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Links to other interesting threads:
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· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
Aerial farms like that were the norm in the 60's for overseas telecommunications before undersea cables and satellites.
Then came the huge satellite dishes with cryogenic cooling on the back of the dish for the LNA's (low noise receivers) which is when they discovered microwaves cooked the birds flying in front of them. A few years later they had improved the receivers enough that the receivers could be in a building and refrigeration was no longer required. I saw both at OTC (the phone company) at Ceduna, South Australia in 1971 on one of my training trips. Absolutely fascinating.
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Links to other interesting threads:
· Home of the MultiBladeProps: TriBlade,·RamBlade, RetroBlade,·TwinBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
Post Edited (Cluso99) : 10/1/2009 9:44:38 PM GMT