The pre-selector rejects unwanted out of band interference from multi-multi operation or strong broadcast stations, as your first line of defence against interfering signals. The pre-selector automatically tracks the intended signal, keeping the pre-selector’s bandwidth centred on the operating frequency at several kHz steps (minimum). The pre-selector works from 1.5MHz to 30MHz. The two roofing filters dramatically improve the blocking characteristics from strong adjacent signals. This is not an optimal design for SSB, CW, or AM modes. Typically, transceivers use only one broad 15 kHz roofing filter for all modes.
The IC-7800 switches between these two roofing filters depending on operating mode. One is 15 kHz filter for FM mode and the other is 6kHz filter for SSB, CW, AM and data modes. The IC-7800 has two roofing filters before the 1st IF amplifier stage. The mechanical relay prevents 2nd order distortion at the primary stage of signal processing. The IC-7800 uses highly reliable and durable mechanical relays for BPF switching instead of non-linear semi-conductors which cause distortion. Mechanical relay BPF (Band Pass filter) switching and two roofing filters This allowed us to explore new technical dimensions such as a double conversion super-heterodyne system, mechanical relay BPF switching and two roofing filters. To achieve this superior receiver performance, Icom’s engineering team completely reviewed the whole analogue circuit and matched it to the DSP units. Icom’s 40 years of analogue 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. The receivers combine various current and new technology, to obtain the +40dBm IP3. The result is 110dB dynamic range, +40dB 3rd order intercept point in HF bands and other phenomenal performance features. Icom has developed the flagship model IC-7800 which is a fusion of forty years analogue RF circuit development expertise, with cutting edge digital technology. Ham radio stations increasingly use high power and high gain antennas that raise the field strength of unintended signals, and thus require a wider receiver dynamic range. Its heritage has always been based on technical excellence from the first analogue PLL circuit in the IC-200, to the ground-breaking 32-bit floating point DSP of the IC-756PRO.
ICOM IC 7800 MODS UPDATE
You can also hear a beep when tuning out of, or into the programmed Amateur band. Enables the operator to program custom band-edge frequencies.Adds the ability to send VOICE memory, in the SSB mode, or CW memory keyer contents, in the CW mode, by pushing one of the F1 – F4 keys on an external USB keyboard.(More details of the external keypad are described on page 2-6 of IC-7800 instruction manual.) Adds the ability to send TX memory contents, while operating in either the RTTY mode, or the PSK31 mode, pushing one of the 4 keys on an external keypad.
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