Whisper

Picked up one of these ...



Setup was a breeze less then 5 minutes I was on 80m and this is the initial result....

and a little about the modulation ...

. WSPR software utilizes an extremely narrow frequency band with specially-coded forward error correcting (FEC) and frequency shift keying (FSK). FSK is like very narrow band FM. This technique reduces errors and improves the possibility of copying the message in noise. The signal fits into a tiny 200 Hz segment. Within each segment, the signal bandwidth is only 6 Hz. This allows several tens of stations to coexist in a segment with minimal interference. There are 12 segments presently (denoted here as the WSPR bands), located within the radio frequency spectrum (see Figure 2). The WSPR protocol is extremely effective at signal-tonoise ratios as low as –28 dB in a 2,500 Hz bandwidth. This is over 10 dB below the threshold of audibility. In other words, you can sometimes copy signals that you cannot hear. It is because of this capability that even low power WSPR signals can be decoded in the farthest reaches of the globe. WSPR is designed to do just one thing: find a communication path. It communicates via specially formatted messages aimed at determining if a propagation path is open on a given transmitting frequency. Formatting contains a name, four character grid locator, and power level in dBm (decibels relative to one milliwatt). This information is compressed into 50 binary digits and encoded using a convolutional code of length 32 and rate 1/2. The resulting 162 bits are transmitted using four tone FSK at 1.46 baud. The least significant bit is defined by a pseudorandom sequence known by the software at both transmitter and receiver. It is used to establish accurate time and frequency synchronization. Long convolutional codes are advantageous since undetected decoding errors are rare. Normally, a Viterbi algorithm is used for decoding but due to complexity, the WSPR decoder uses a special sequential algorithm. When a station is decoded, other information such as “receive location,” name, S/N ratio, and DT (time difference) is routinely logged. This information can be automatically downloaded to WSPRnet.org using the “spots” option. Your name will then be shown on a flag on a world map with others. Options on the website can be used to find the distance and direction of the station received.