HF Modem   
     The PRI-4400 HF modem is a reliable, fast and accurate data communication device complying with MIL-STD-188-110A standard. It is widely applied as a digital communication device in geology, mining, petroleum, telecommunication, police and island etc. A HF radio can realize digitalized communication through a HF modem. It can send and receive voice, data or fax.
Specifications
  • Communication rate:
    4800bps、2400bps、1200 bps、600bps、300bps、150 bps、75 bps。
  • Synchronous terminal data rate：
    4800bps、2400bps、1200 bps、600bps、300bps、150 bps、75 bps。
  • Asynchronous terminal data rate：
    9600bps、4800bps、2400bps、1200bps、600bps、300bps、150 bps。
  • Asynchronous data stream control：RTS control、X-on / X-off control。
  • Doppler frequency shift：Initial value±75Hz, ±3.5Hz/s。
  • Interleaving time：0、0.6s、4.8s。
  • Error control：forward error correction
  • Under white noise condition, bit error rate is less than the value showing in the table 1.
Table 1 HF Modem’s Performance under white noise
 
    Rate bps
    SNR dB
    Bit Error Rate
    2400
    9
    1.00E-04
    1200
    6
    1.00E-04
    600
    3
    1.00E-04
    300
    1
    1.00E-04
    150
    -1
    1.00E-04
    75
    -3
    1.00E-04
  • HF modem’s performance under different conditions. The power of signal and noise is measured within the bandwidth of 3kHz, while in fading channel it’s the value of long interleaving.
Table 2 HF Modem’s Performance under Different Conditions
 
    Rate bps
    Channel numbers
    Multi-path (ms)
    fading bandwidth（Hz）
    SNR（dB）
    Bit Error Rate
    4800
    One fixed
    -
    -
    17
    1.00E-03
    4800
    Two fading
    2
    0.5
    27
    1.00E-03
    2400
    Two fading
    -
    -
    10
    1.00E-05
    2400
    Two fading
    2
    1
    18
    1.00E-05
    2400
    Two fading
    2
    5
    30
    1.00E-03
    2400
    Two fading
    5
    1
    30
    1.00E-05
    1200
    Two fading
    2
    1
    11
    1.00E-05
    600
    Two fading
    2
    1
    7
    1.00E-05
    300
    Two fading
    5
    5
    7
    1.00E-05
    150
    Two fading
    5
    5
    5
    1.00E-05
    75
    Two fading
    5
    5
    2
    1.00E-05
  • Synchronizing time：600ms(short interleaving)、4.8s(long interleaving)。
  • Channel bandwidth：300Hz ~3000Hz。
  • Audio output：-16 dBm～-3dBm,600Ω±10% balance or unbalance。
  • Audio input：-25 dBm～+10dBm,600Ω±10% balance or unbalance。
 

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