IC-7800

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Icom's 40 years of analog RF circuit experience combined with cutting edge digital technology results in an astonishing 110dB receiver dynamic range and a +40dBm IP3 in the HF bands. A first in Ham radio! To achieve this superior receiver performance, Icom's engineering team completely reviewed the whole analog circuit and matched it to the DSP units. This allowed us to explore new technical dimensions such as a double conversion super-heterodyne system, mechanical relay BPF switching and two roofing filters.
 

The IC-7800 uses highly reliable and durable mechanical relays for BPF switching instead of non-linear semi-conductors which cause distortion. The mechanical relay prevents 2nd order distortion at the primary stage of signal processing. The IC-7800 has two roofing filters before the 1st IF amplifier stage. One is 15kHz fileter for FM mode and the other is 6kHz filter for SSB, CW, AM and data modes. The IC-7800 switches between these two roofing filters depending on operating mode. Typically, transceivers use only one broad 15kHz roofing filter for all modes. This is not an optimal design for SSB, CW, or AM modes. The two roofing filters dramatically improve the blocking characteristics from strong adjacent signals.
 

The pre-selector works from 1.5MHz to 30MHz. The preselector automatically tracks the intended signal, keeping the pre-selector�fs bandwidth centered on the operating frequency at several kHz steps (minimum). The preselector rejects unwanted out of band interference from multi-multi operation or strong broadcast stations, as your first line of defense against interfering signals. The center frequency of the pre-selector is adjustable from the DIGI-SEL tuning knob on the front panel.

Double conversion super-heterodyne system

While mixers often become a cause of signal distortion and spurious emissions, the IC-7800 utilizes a double conversion super-heterodyne system using a newly developed image rejection mixer. A high performance D-MOS FET array for the 1st mixer stage is infused with a signal from the high-level C/N, high-drive Local Oscillator from the PLL unit. This new mixer reduces signal distortion through IF processing and provides a high-fidelity signal to the DSP unit. AGC loop management using the DSP unit The IC-7800 has two types of AGC loops. One of the AGC loops detects the AGC voltage at the BPF input in the DSP unit and feeds back to the 1st IF amplifier. This AGC loop prevents the saturation of the 1st IF amplifier from strong signals out of the BPF bandwidth, and improves the dynamic range against adjacent signals. The other AGC loop detects the AGC voltage at the digital IF filter output which has only passed the intended signal and draws the full potential from the digital IF filter. Combining the digital IF filter, manual notch, and the 1st IF stage, these are all controlled by the DSP unit. 110dB of ultra wide dynamic range in the receiver means the IF amplifier is distortion free from strong signals. AGC Volume knob for fine tuning In addition to the preset AGC time constants (slow, medium and fast), the manual AGC volume provides flexible detailed AGC tuning.

The ultimate dual receiver performance is at your control; the receivers are completely independent all the way from the 4 antenna jacks, through the pre-selectors, DSP, signal detectors, front panel control, and right into the stereo headphone! The dual receiver allows you to receive two different bands simultaneously in different modes, with each receiver not causing any adverse affect to the other one. This true dual receiver takes your band hopping and contesting experience to the next level!
 

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