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A receiver will pick up the raido signal plus background noise (most notably cosmic background radiation). Generally the received noise power is greater for greater receiver bandwidth. So to get a good signal to noise ratio one can transmit the radio signal within a very narrow frequecy band and put a very narrow band filter on the front of the receiver.

EXAMPLE: The receiver was picking up 1 micro-watt of radio signal and 1 milli-watt of noise power with a 1MHz bandwidth (so a SNR of 0.001).

Droping the bandwith to 10Hz would result in 1 micro watt of radio signal power and 10 nano-watts of received noise power (so a SNR of 100)

Consider a protocol like PSK31 (or similar) used by HAM radios instead of moorse code.

PSK31 uses pure tones of relatively long duration to send 1s and 0s. The longer those tones are the more narrow the filter at the receiver can be. PSKxxx can be used to send low data rate messages across the plannet using only a few watts of power.

Another alternative (though more complex) is using long strings of physical 1s and 0s to represent a single symbol in the protocol. This method is used by GPS for example. It has for example. The GPS signal is normally about 30X lower power than the background noise, but by correlating long strings of 1024 bits the receiver is able to on average lock onto the signal.

EXAMPLE: Define two long sequences of physical 1s and 0s for each letter of the alphabet. Each code is very different from the other codes.
Let A be 00101010 10001010 10100101 00101010 ...
Let B be 10100001 10100101 00010101 00010100 ...
Let C be 01001010 01010100 00010100 00110101 ...

The sequences may be thousands of bits long if you want. The patterns are generated by a computer automatically when the user types a letter on the keyboard.

The physical bit sequences are sent at a much higher rate than the actual symbols. For example if you want t send one symbol per second and your sequences are 1000 bits long then you send the physical bits at 1000 bits per second.

When receiving the signal + noise; the noise will cause the receiver to make the wrong decision on the physical 1s and 0s some percentage of the time. The receiver stores the received bit pattern and compares it to one of the codes. The receiver then selects the code which most closely matches the received pattern. Even if most of the received bits are wrong, the received code is likely to match most closely to the code sent by the transmitter rather than one of the other codes. Thus the receiver can determine what the transmitter sent even if the background noise is much higher than the received radio signal.

Some other advantages of using long codes is that the codes inherently correct physical bit errors at the receiver. Also different transmitters can each use different code sets so they can talk at the same time (this approach is how CDMA cell phones work).

A receiver will pick up the raido signal plus background noise (most notably cosmic background radiation). Generally the received noise power is greater for greater receiver bandwidth. So to get a good signal to noise ratio one can transmit the radio signal within a very narrow frequecy band and put a very narrow band filter on the front of the receiver.

EXAMPLE: The receiver was picking up 1 micro-watt of radio signal and 1 milli-watt of noise power with a 1MHz bandwidth (so a SNR of 0.001).

Droping the bandwith to 10Hz would result in 1 micro watt of radio signal power and 10 nano-watts of received noise power (so a SNR of 100)

Consider a protocol like PSK31 (or similar) used by HAM radios instead of moorse code.

PSK31 uses pure tones of relatively long duration to send 1s and 0s. The longer those tones are the more narrow the filter at the receiver can be. PSKxxx can be used to send low data rate messages across the plannet using only a few watts of power.

Another alternative (though more complex) is using long strings of physical 1s and 0s to represent a single symbol in the protocol. This method is used by GPS for example. It has for example. The GPS signal is normally about 30X lower power than the background noise, but by correlating long strings of 1024 bits the receiver is able to on average lock onto the signal.

EXAMPLE: Define two long sequences of physical 1s and 0s for each letter of the alphabet. Each code is very different from the other codes.
Let A be 00101010 10001010 10100101 00101010 ...
Let B be 10100001 10100101 00010101 00010100 ...
Let C be 01001010 01010100 00010100 00110101 ...

The sequences may be thousands of bits long if you want. The patterns are generated by a computer automatically when the user types a letter on the keyboard.

When receiving the signal + noise; the noise will cause the receiver to make the wrong decision on the physical 1s and 0s some percentage of the time. The receiver stores the received bit pattern and compares it to one of the codes. The receiver then selects the code which most closely matches the received pattern. Even if most of the received bits are wrong, the received code is likely to match most closely to the code sent by the transmitter rather than one of the other codes. Thus the receiver can determine what the transmitter sent even if the background noise is much higher than the received radio signal.

Some other advantages of using long codes is that the codes inherently correct physical bit errors at the receiver. Also different transmitters can each use different code sets so they can talk at the same time (this approach is how CDMA cell phones work).

A receiver will pick up the raido signal plus background noise (most notably cosmic background radiation). Generally the received noise power is greater for greater receiver bandwidth. So to get a good signal to noise ratio one can transmit the radio signal within a very narrow frequecy band and put a very narrow band filter on the front of the receiver.

EXAMPLE: The receiver was picking up 1 micro-watt of radio signal and 1 milli-watt of noise power with a 1MHz bandwidth (so a SNR of 0.001).

Droping the bandwith to 10Hz would result in 1 micro watt of radio signal power and 10 nano-watts of received noise power (so a SNR of 100)

Consider a protocol like PSK31 (or similar) used by HAM radios instead of moorse code.

PSK31 uses pure tones of relatively long duration to send 1s and 0s. The longer those tones are the more narrow the filter at the receiver can be. PSKxxx can be used to send low data rate messages across the plannet using only a few watts of power.

Another alternative (though more complex) is using long strings of physical 1s and 0s to represent a single symbol in the protocol. This method is used by GPS for example. The GPS signal is normally about 30X lower power than the background noise, but by correlating long strings of 1024 bits the receiver is able to on average lock onto the signal.

EXAMPLE: Define two long sequences of physical 1s and 0s for each letter of the alphabet. Each code is very different from the other codes.
Let A be 00101010 10001010 10100101 00101010 ...
Let B be 10100001 10100101 00010101 00010100 ...
Let C be 01001010 01010100 00010100 00110101 ...

The sequences may be thousands of bits long if you want. The patterns are generated by a computer automatically when the user types a letter on the keyboard.

The physical bit sequences are sent at a much higher rate than the actual symbols. For example if you want t send one symbol per second and your sequences are 1000 bits long then you send the physical bits at 1000 bits per second.

When receiving the signal + noise; the noise will cause the receiver to make the wrong decision on the physical 1s and 0s some percentage of the time. The receiver stores the received bit pattern and compares it to one of the codes. The receiver then selects the code which most closely matches the received pattern. Even if most of the received bits are wrong, the received code is likely to match most closely to the code sent by the transmitter rather than one of the other codes. Thus the receiver can determine what the transmitter sent even if the background noise is much higher than the received radio signal.

Some other advantages of using long codes is that the codes inherently correct physical bit errors at the receiver. Also different transmitters can each use different code sets so they can talk at the same time (this approach is how CDMA cell phones work).

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A receiver will pick up the raido signal plus background noise (most notably cosmic background radiation). Generally the received noise power is greater for greater receiver bandwidth. So to get a good signal to noise ratio one can transmit the radio signal within a very narrow frequecy band and put a very narrow band filter on the front of the receiver.

EXAMPLE: The receiver was picking up 1 micro-watt of radio signal and 1 milli-watt of noise power with a 1MHz bandwidth (so a SNR of 0.001).

Droping the bandwith to 10Hz would result in 1 micro watt of radio signal power and 10 nano-watts of received noise power (so a SNR of 100)

Consider a protocol like PSK31 (or similar) used by HAM radios instead of moorse code.

PSK31 uses pure tones of relatively long duration to send 1s and 0s. The longer those tones are the more narrow the filter at the receiver can be. PSKxxx can be used to send low data rate messages across the plannet using only a few watts of power.

Another alternative (though more complex) is using long strings of physical 1s and 0s to represent a single symbol in the protocol. This method is used by GPS for example. It has for example. The GPS signal is normally about 30X lower power than the background noise, but by correlating long strings of 1024 bits the receiver is able to on average lock onto the signal.

EXAMPLE: Define two long sequences of physical 1s and 0s for each letter of the alphabet. Each code is very different from the other codes.
Let A be 00101010 10001010 10100101 00101010 ...
Let B be 10100001 10100101 00010101 00010100 ...
Let C be 01001010 01010100 00010100 00110101 ...

The sequences may be thousands of bits long if you want. The patterns are generated by a computer automatically when the user types a letter on the keyboard.

When receiving the signal + noise; the noise will cause the receiver to make the wrong decision on the physical 1s and 0s some percentage of the time. The receiver stores the received bit pattern and compares it to one of the codes. The receiver then selects the code which most closely matches the received pattern. Even if most of the received bits are wrong, the received code is likely to match most closely to the code sent by the transmitter rather than one of the other codes. Thus the receiver can determine what the transmitter sent even if the background noise is much higher than the received radio signal.

Some other advantages of using long codes is that the codes inherently correct physical bit errors at the receiver. Also different transmitters can each use different code sets so they can talk at the same time (this approach is how CDMA cell phones work).