The DBA 270 is a low-noise and large-signal-proof dual-band mast preamplifier for the amateur radio bands 2 m and 70 cm. It is used to improve the signal reception of amateur radio stations in the two bands. This amplifier is suitable for the connection of dual-band antennas with a feed line. When using monoband antennas, an antenna switch must be used at the input of the amplifier.
In order to avoid mutual interference with signals from the two frequency ranges, the DBA 270 is constructed with separate amplifier stages (split band), which are connected with diplexer circuits at the input and output of the device. Due to this wiring, only one RF socket is required for connecting the dual-band antenna and the cable to the radio.
The preamplifier is equipped with a transmit and receive switch. The automatic transmit / receive switchover (VOX) switches the amplifier off when transmitting and on again when receiving. The maximum switchable power in VOX operation is 100 watts. In the case of higher outputs, the amplifier is controlled and supplied with voltage with the aid of a sequencer. When using a sequence control, the maximum transmittable transmission power is 750 W PEP and 400 W with CW / FM / WSJT. This amplifier can be powered remotely via the coaxial cable through its output with supply voltage. Alternatively, local power supply can be provided via the UHF socket with a separate line. When using the VOX switching, this amplifier must have a permanent power supply during operation. It can be supplied locally or remotely.
The input and output of this amplifier are secured with amplitude limiters to ensure a high level of operational reliability. The input and output circuitry of the amplifier is dimensioned so that both connections have an exact 50 ohm impedance with very low imaginary components. This ensures that the antenna system is loaded with real 50 ohms and that the parameters of the system are not changed. With the currently mostly used, highly optimized narrow-band antennas, it is very important that they are terminated with real 50 ohms. A mismatch at the input of the preamplifier used would lead to a change in the parameters of such antennas, causing loss of profit.
This amplifier is equipped with a UV-resistant, weatherproof housing and N sockets. Hot-dip galvanized clamps and assembly material made of stainless steel are included in the scope of delivery.
|Technical data||DBA 270|
|Frequency range:||144-146 MHz; 430-440 MHz|
|Noise figure (20°C, NF):||1,0 dB / 2 m; 1,0 dB / 70 cm|
|Gain (+/-1%) (S21):||16 dB / 2 m; 24 dB / 70 cm|
|Max. switching power with RF VOX:||200 W PEP SSB
100 W CW, FM, WSJT, FT8
|Transferable power when using a sequencer:||750 W PEP SSB
400 W CW, FM, WSJT, FT8
|Insertion loss:||0,1 dB / 2m; 0,2 dB / 70 cm|
|Return loss when transmitter is active:||30 dB / 2m; 40 dB / 70 cm|
|Input return loss RX (S11):||20 dB / 2m; 18 dB / 70 cm|
|Output return loss RX (S22):||18 dB / 2m; 18 dB / 70 cm|
|Output IP3:||25 dBm / 2 m; 27 dBm / 70 cm|
|Input IP3:||9 dBm / 2 m; 3 dBm / 70 cm|
|Supply voltage:||12-14 V|
|Current consumption:||260-280 mA|
|Mast diameter:||max. 58 mm|
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