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+40dBm IP3 (3rd Order Intercept Point)
The IC-7851 continues the +40dBm, 3rd order intercept point and 110dB receiver dynamic range benchmark set by the IC-7800. To achieve this superb receiver performance, the entire analog circuitry and components have been re-engineered to match the DSP units. A newly designed LO amplifier generates high output while keeping flat frequency characteristics over a 60MHz wide range.
Dynamic Range Characteristics
Dynamic Range (typical)
BPF Switching: Mechanical Relays
The IC-7851 incorporates high-grade, long-term reliable mechanical relays rather than PIN diodes for switching the Band Pass Filters (BPF). This deployment of relays removes secondary distortion products from the primary stage of signal processing.
Four 1st IF “Roofing” Filters
Three high-spec 1st IF “roofing” filters plus the new 1.2kHz Optimum Roofing Filter allow only signals within the filter passband to the 1st IF amplifier stage. You can select the filter width from 15kHz, 6kHz, 3kHz and 1.2kHz, depending on your operating mode. (FM mode is fixed at 15kHz)
1.2kHz Optimum Roofing Filter
3, 6, 15kHz High-Spec 1st IF filters
The preselector works between 1.5MHz and 30MHz and rejects distortion components derived from out of band interference such as multi-multi operation or strong broadcast stations. It automatically tracks the intended signal keeping the preselector’s bandwidth centered on the operating frequency. The center frequency of the preselector is manually adjustable from the DIGI-SEL tuning knob on the front panel.
Automatic Preselector Bandwidth Characteristics
Triple DSP Power
Three separate 24-bit AD/DA converters and dedicated DSP processors are at the heart of the IC-7851. With one AD/DA and DSP dedicated to the spectrum scope and two 24-bit AD/DA and DSP chips for the receivers and transmit circuits, there is plenty of DSP power for the most demanding RF environment.
Transmit/Receiver DSP (left) and Receiver DSP (right)
ADSP-21489 by Analog Devices
32-bit floating point DSP
393 MHz clock speed