Pre Amplifier

HF_BROADBAND_ANTENNA_PREAMP

Published:2009/6/15 21:06:00 Author:May

The HP/SW receiver preamplifier is comprised of a broadband toroidal transformer (L1-a and L1-b), LC network (corrtprised of a 1600-kHz, high-pass filter and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon Associates 7-50-2, red, toroidal core), a pair of resistive attenuators (ATTN1 and ATTN2), and a MAR-x device.Shown here is the composition of a basic 1-dB pi-network resistor antenuator. This is the method of supplying dc power to a preamplifier using only the RE coax cable.   (View)

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WIDEBAND_ANTENNA_PREAMPLIFIER

Published:2009/6/15 21:02:00 Author:May

This wideband antenna preamplifier has a gain of around 20 dB from 40 to 860 MHz, covering the entire VHF, FM, commercial, and UHF bands. A phantom power supply provides dc to the preamp via the coaxial cable feeding the unit.   (View)

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VLF_60_kHz_ANTENNA_PREAMP

Published:2009/6/15 20:57:00 Author:May

Suitable for 60-kHz standard frequency reception, here is a schematic for a FET preamp and antenna.   (View)

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GENERAL_PURPOSE_PREAMPLIFIER

Published:2009/6/15 4:08:00 Author:May

Suitable for general audio use, the preamp circuit uses a feedback pair. Current gain is set by the ratio of (R4 + R6)/R4.   (View)

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AUDIO_TO_UHF_PREAMP

Published:2009/6/15 3:57:00 Author:May

The Signetics NE5204 or NE5205 can be used in this AF to 350-MHz (-30 dB) preamp. If 600MHz @ 3dB is needed, use the NE5205. The noise figure is 4.8dB at 75Ω, 6dB at 50Ω. Gain is approximately +20dB over the passband.   (View)

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FREQUENCY_COUNTER_PREAMP

Published:2009/6/15 3:56:00 Author:May

Based on the LM733 or NE592, the preamp shown has a bandwidth of 100 MHz. The FET inputs provide about 1-MΩ input impedance. Q4, Q5, and IC2 provide signal conditioning.   (View)

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GENERAL_PURPOSE_JFET_PREAMP

Published:2009/6/15 3:31:00 Author:May

This JFET preamplifier has a gain of about 20dB and a bandwidth of over 100kHz. It is use-ful as a low-level audio amplifier for high-imped-ance sources.   (View)

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