Modems used for packet radio vary in throughput and modulation technique, and are normally selected to match the capabilities of the radio equipment in use. Most commonly used method is one using audio frequency-shift keying (AFSK) within the radio equipment's existing speech bandwidth. The first amateur packet radio stations were constructed using surplus Bell 202 1,200 bit/s modems, and despite its low data rate, Bell 202 modulation has remained the standard for VHF operation in most areas. More recently, 9,600 bit/s has become a popular, although more technically demanding, alternative. At HF frequencies, Bell 103 modulation is used, at a rate of 300 bit/s.
modems used for packet radio vary in throughput and modulation technique and are normally selected to match the capabilities of the radio equipment in use most commonly used method is one using audio frequency-shift keying (afsk) within the radio equipment's existing speech bandwidth the first amateur packet radio stations were constructed using surplus bell 202 1200 bit/s modems and despite its low data rate bell 202 modulation has remained the standard for vhf operation in most areas more recently 9600 bit/s has become a popular although more technically demanding alternative at hf frequencies bell 103 modulation is used at a rate of 300 bit/s