Model PRE-2
Remote-Powered Preamplifier With 1.8-8.0 MHz Filter

The PRE-2 preamplifier is intended for outdoor or other locations where the DC power will be provided via the coaxial cable. The unit has a nominal 12 dB gain, and includes a highpass/lowpass filter combination that rejects signals below 1.8 MHz and above 8.0 MHz. The passband includes the 160, 80/75 and 40 Meter amateur bands, and all frequencies in between. When power is removed, a relay bypasses the unit, allowing the antenna to be used on other frequencies. The preamp circuit is a classic negative feedback type with emitter degeneration, biased to approximately 60 mA for good dynamic range performance. Similar circuits have been described by several authors in both amateur radio and professional literature. The filter has an elliptic highpass section, followed by a Chebyshev lowpass section. The filter provides good rejection of the AM broadcast band below 1600 kHz, and shortwave frequencies above the 8 MHz upper passband edge.

Specifications
Amplifier type:  NPN transistor with negative feedback and emitter degeneration
Highpass filter:  Elliptic function, typical 45 dB or more rejection at frequencies below 1450 kHz
Lowpass filter:  Chebyshev with typical 43 dB rejection at 12 MHz
Gain:  12 dB ±1.5 dB (within filter passband of 1.8 to 8.0 MHz)
Input/ouput impedances:  50 ohms nominal
In/out switching:  Preamp is bypassed when power is removed
Power requirements:  +12 to 13.8 VDC @ 125 mA, switched (provided by customer)
DCB-1 DC Block:  Injects DC power to coax, isolates the DC from the receiver
Power indication:  LED adjacent to the powered connector
Connectors (outdoor unit):  (2) SO-239
Connectors (DC Block):  (2) phono ("RCA") connectors for coax; 2.1 mm DC power jack

Installation Notes
The PRE2 has a typical bandpass as shown in the measurement below:

Installation Notes
The preamp mounting bracket should be grounded, and the antenna used with the preamp should include lightning/surge protection. Surge protection is not included with the preamp because that type of protection should be installed at the antenna. Although the preamp has a weather-resistant enclosure, additional weather protection is advised, including weatherproofing connectors of the coaxial cables.

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