CHIP comes in two flavors CHIP64 and CHIP128 , The Chip is bases upon a digital scheme called SS (Spread-Spectrum) So , Why use a SS scheme? It is designed to help increase baud and keep stability to the mode due to ionspheric disturbances. usually low baud modes are slightly better on signal to noise ratio but much slower, the CHIP scheme is trying to over come some of this. What is Spread Spectrum exactly you may ask. One way you could explain it is that it use more bandwidth than traditional digital schemes in the miltary they use this scheme to hid the meaning of the message but in CHIP mode it is intended for cause less errors using the DSSS (Direct Sequence Spread Spectrum)scheme.In a DSSS transmission, the low speed signal containing the data bits to be transmitted is mixed (multiplied) with a greatly higher speed signal called code. The result of this mixing operation, named spreading, is a high-speed bit stream which is then transmitted as a normal DBPSK. Indeed, a DSSS signal looks like nothing else than a MT63 signal
autocorrelation is the most important as it allows to identify the code within the arriving bit sequence. With a simple operation of multiplication, called despreading, it’s possible, instant by instant, to determine if the code is presenting on the receive bit stream. Despreading operations are done in a block called correlator, whose output indicates the likelihood that the code has arrived in that particular instant. Codes of greater length have better autocorrelation properties with less chance of false guesses.
Bandwidth= around 580hz
Chiprate : 300/second (a "chip" is here a "bit" from the point of view of the modulation)
Bits rate (after pseudo WHP inverse transform) : 37.5 per second in CHIP64 and 21.09 in CHIP128
Speed (words) : 48 wpm in capital letters to 68 wpm in small letters (average in CHIP64)
27 wpm in capital letters to 38 wpm in small letters (average in CHIP128)
Modulation : DBPSK
A "block" is composed of 64 chips in Chip64 and 128 in Chip128. A block corresponds to a code on 8 bits in Chip64 and 9 bits in Chip128. The block is obtained from the code, by a WHP transform "Walsh-Hadamard-Porcino", so as:
* to give a good autocorrelation quality necessary for the "block" synchronization, using an "m-sequence"
* a weak intercorrelation between codes to distinguish them, using a Walsh-Hadamard transform.
In Chip64, for the codes between 0 and 127, it will be used the m-sequence[6,5,2,1] for odd codes and the m-sequence[6,5] for the even codes.
In Chip128, for the codes between 0 and 255, it will be used the m-sequence[7,3,2,1] for odd codes and the m-sequence[7,3] for the even codes.
Reception mode : indifferent (LSB or USB)
Character set : ASCII characters + almost all ANSI extended characters + an error reset character (« Varicode » characters)
Shape of pulse : raised cosine
Synchronization : automatic using the signal
Correction code : the use of the WHP transform is equivalent to a a powerful "block" coding type
Convolution code : no,
Interleaving : no
Drift tolerance : 15 Hz/minute (+/- depending on signal level)
Pmean/Ppeak : 0.79
Lowest S/N : - 8 dB
FFT Screen Shot
Mode Audio Sample
CHIP64 VIDEO OF ACTUAL QSO HERE