MDR: 110 dB Now Icom raises the bar

Icom HF engineers have improved the design of the local oscillator (LO) so that the IC-7851 can set a new quality standard for amateur radio receivers. The goal was to greatly reduce the phase noise that impairs the final signal due to the sum of all the radio signals present. The result was an RMDR of 110 dB*1. The comparison below shows the improvements compared to the IC-7800.
RMDR

Rmdr (Reciprocal Mixing Dynamic Range) is the relative level of an unwanted signal at the frequency distance "n" kHz where background noise increases by 3 dB. The phase noise of the local oscillator is mixed with strong unwanted signals to create an inevitable noise, drowning the desired signal.
1.2 kHz roofing filter

Despite the trend of moving to demixture or combined frequency conversion in receiver design, Icom relies on stable performance designs that mix to higher frequency. The IC-7851 introduces an optimal 1.2 kHz roofing filter, providing great performance improvement in the event of near-frequency disruptions. The newly developed filter solves the need for a narrower roofing filter in receivers that mixes upwards.
Local oscillator construction

The IC-7851 goes beyond the boundaries of traditional constructions by using direct digital synthesis (DDS) together with a phase-locked oscillator for lo (local oscillator).
The C/N value is much better than that of ic-7800 and other HF transceiers in the same class. The design provides significantly smaller noise components both during reception and transmission.
Improved phase noise properties

Phase noise is closely related to the design of radio circuits and the new solution for LO introduced in the IC-7851 involves major improvements in the use of the receiver design with upward mixing to the mid-frequency 64 MHz, introduced with the IC-7800. The IC-7851 provides an impressive improvement of 20 dB when measured at 10 kHz frequency deviation, and over 30 dB improvement when measured at 1 kHz compared to IC-7800.
Improved spectrum display

The IC-7851 uses a dedicated DSP device for fast fouriertransform (FFT) of the spectrum. A 2250 MFLOPS DSP processor enables a new dual scope feature and delivers significantly higher sweep speeds and higher accuracy than the IC-7800.
+40 dBm IP3 (Third Order Intercept Point)

THE IC-7851 has the same good third-order intercept point with +40 dBm and 110 dB dynamic range achieved by IC-7800. To achieve this excellent performance in the receiver, all analog circuits and components have been redesigned to fit with the DSP devices. A newly developed LO amplifier provides high output signal while maintaining straight frequency range over a 60 MHz wide spectrum.
Dual spectrum display

The IC-7851 introduces a new dual display with the ability to display both receivers in a spectrum display. The dual spectrum display feature is crucial for winning multiples and detecting tape openings during the contest or to be able to work with all frequency bands and modes of traffic on a DXp edition. The waterfall view shows the change in signal strength over time. This allows you to see signals that can be difficult to detect in a standard spectrum display.
200 W power output

The push-pull amplifier uses the POWER MOS-FET powered by 48 V DC. It can handle powerful 200W continuous power output. An efficient cooling system ensures to maintain the internal temperature.
Digital midfrequency filter

Icom's digital mid-frequency filter gives you performance that cannot be achieved with crystals or mechanical filters. They allow the operator to select the filter shape (sharp or soft edges), filter bandwidth, and center frequency properties.
Other outstanding features

Antenna and receiver

    Two completely independent receivers
    Four roofing filters at first intermediate frequency: 15 kHz, 6 kHz, 3 kHz and 1.2 kHz
    Four antenna connectors with automatic antenna selection
    Automatic antenna tuning unit
    Special preamp and mixer for 50 MHz
    Manual digital notch
    Dual digital PBT eliminates interference from nearby signals
    New automatic digital noiseblanker
    ±0.05 ppm High car OCXO unit (crystal oven)

CW mode

    DSP-controlled CW whim with waveforming
    Multifunction electric bug with adjustable sneering speed, dash ratio between manipulator polarity
    Adjustable audio peak filter (soft/sharp)


Use

    Memory with high-quality digital voice recording
    Integrated support for RTTY, PSK31 and PSK63 without the need for a computer
    Message memory for CW, RTTY and PSK33
    Digital Video Interface (DVI-I)
    Card reader for SD memory card
    Audioscope function
    Control spectrum display with one click
    AGC control
    Microphone equalizer and adjustable transmitter bandwidth
    FFT scope leveling for decoding PSK and RTTY
    Screen saver