Type of Receiver

The HDR-2005 is a simple homebrew HF receiver for approximate 100 kHz to 30 MHz. It is a direct conversion receiver with an I/Q quadrature sampling detector, phase shift (polyphase) network, AF filters, AF AGC and AF amplifier. At the front end there are an attenuator, a band switched BPF and a switchable HF preamplifier.

RF Front End

50 Ohm antennae input. Simple protection circuit and switched attenuator. Relay-switched BPF. Optional switchable HF preamplifier (2N5109).

Quadrature Detector

30 MHz LPF (Amidon T50-2). Double balanced quadrature sampling detector (FST 3253, 4 x 68n caps). PreAmplifier (2 x INA163) with GainControl (3 steps: 20, 40, 55 dB).
One disadvantage of this quadrature detector is a proper impedance matching on the RF side. In the HDR-2005 I use for this reason a 1:4 transformation (Balun) and a "50 Ohm anchor" (this attenuator caused a little change for the worse of the noise figure, but I think its necessary for constant matching).

Phasing filter - Demodulation - AF BPF

SSB/AM line switch (HEF4053). Active polyphase network (4 x NE5532). Sideband demodulation (1/2 NE5532). 3.5 khZ LPF (1/2 NE5532). Switched capacitor BPF 250 Hz - 3 kHz (2 x LMF100). Passive 3.5 kHz LPF (with real LC). Simple AM demodulation and active 10 kHz LPF (TL074).

Audio AGC - Audio Amp

AGC (OTA LM13700, TL0x). AF amplifier (TDA2009)

DDS - Quadrature LO

100 MHz Master oscillator. DDS (AD9951). 120 MHz LPF, Post-DDS-Amplifier (ADA-4543). Quadrature modul (74VHC132, 74VHC86, 74VHC74).

uP Control

ATMEL AVR ATmega8515 uC, 4x4 KeyPad, 2x16 LCD, Rotary Encoder (Old Stepper Motor). Firmware with BASCOM.

Power Supply

Traditional Main-PowerSupply (+5V, -5V, +12V, -12V) and DDS-PowerSupply (+3.3V, 1.8V, 1.8V)

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