Dual NPN mixer RF circuit (Dual NPN mixer RF circuit): Two NPN transistors.
PufangTech`s VHF radio modems operate in 136~174MHz and 220~240MHz frequency band. The VHF Radio Modem has an air data rates of 19200bps in 25kHz channel spacing and 9600bps in 12.5kHz.
Suitable to apply in data collecting, and VHF radio modems have been used to transmit voice and radio data since the middle of last century. This is one of the most efficient ways to communicate over miles away. A wider coverage is a different advantage belongs to VHF frequency from the others. VHF has 30 to 50 per cent larger range than UHF Radio Modem with the same carrier power.
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Shenzhen PuFang Technology Co., Ltd. , https://www.hytelus.com