HF/50MHz Transceiver
The IC-7700 HF/50MHz transceiver shares many features with its big
brother, the world famous IC-7800. With two independent DSP units, a
+40dBm* 3rd order intercept point and ultra wide dynamic range to name
but a few of the features.
Double conversion super-heterodyne system
While multiple IF stages often become a cause of signal distortion and
spurious emissions, the IC-7700 utilizes a simple double conversion
super-heterodyne system using an 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 mixer reduces signal distortion through IF processing and
provides a high-fidelity signal to the DSP unit.
110dB dynamic range and +40dBm 3rd order Intercept Point (IP3)
The IC-7700 uses mechanical relay BPF switching, digital preselector,
three roofing filters and a simple double super-heterodyne system The
IC-7700 provides superior performance in sensitivity, and a superb
dynamic range of 110dB, +40dBm IP3 (even in strict USB mode (2.4kHz
filter width)).
More than +110dBm 2nd order intercept point (IP2)
More than +110dBm IP2 means the 2nd order distortion from strong broadcast stations will be completely rejected.
* Measurement was made with custom made measuring equipment, due
to normal signal generator (SG) and duplexers are limited to about
+85dBm. The figure of IP2 is typical value
High specification inband IMD
Inband IMD (intermodulation distortion) is undesired modulation (2nd,
3rd or higher order) caused by the non-linear processing of received
multiple signals. The IC-7700 has superior IMD figures. These
differences in the IMD figures will be evident especially in CW mode.
The sound of the received audio will change and you will be able to copy
a weak signal buried in internal distortion or noise.
Band pass filter and mechanical relays
To eliminate as much distortion as possible, the use of semi-conductors
has been reduced to a minimum in the high amplitude switching circuit.
The IC-7700 also uses large coil condensers in the filter structure.
Mechanical relays and large toroidal coils and condensers which are
resistant to magnetic saturation are also used to prevent distortion
before the input of the band pass filter, and provide superior
linearity.
DIGI-SEL (Digital pre-selector) function
The DIGI-SEL function rejects unwanted suppression by out-of-pass band
interference at the primary stage of signal processing. It is useful to
reject unwanted out of band interference from multi-multi operation or
strong broadcast stations. Within the HF bands, the DIGI-SEL
automatically tracks the intended signal at a minimum of 2 kHz steps
keeping the pre-selector�fs bandwidth cantered on the operating
frequency.
The DIGI-SEL has a sharp-pointed very narrow peak characteristic in the
pass band. Together with the band pass filter it greatly attenuates out
of the pass band. This combination reduces 2nd, 3rd and even higher
order IMD components immensely. The centre frequency of the pre-selector
is manually adjustable from the DIGI-SEL tuning knob on the front
panel.
Pre-amplifiers
The IC-7700 has a total of 4 pre-amplifiers, two for HF bands and two
for 50MHz. The purpose of pre-amplifiers is to improve receiver
sensitivity; for the pursuit of higher gain and a better noise figure.
The IC-7700 employs a noiseless feedback design with push-pull
amplifiers. Using feedback transformers, the pre-amplifiers provide a
high IP3 while keeping a low noise figure.
1st mixer
The mixer element SD5400, used in the IC-7700 applies a 16V peak to peak
voltage LO signal. Icom�fs wideband power-amplifier technical knowledge
is used in this mixer to generate such a high-level LO signal.
Two AGC Loops
The IC-7700 has two Automatic Gain Control loops. The first AGC loop
prevents the saturation of the 1st IF amplifier from strong signals out
of the Band Pass Filter bandwidth, and improves the dynamic range
against adjacent signals. The second AGC loop detects the AGC voltage at
the digital IF filter output which only passes the intended signal
without causing AGC blocking. In addition to the preset AGC time
constants (slow, medium and fast), the manual AGC volume provides
flexible detailed AGC tuning.
Three filters including 3kHz
The IC-7700 employs three filters of 15kHz, 6kHz and 3kHz before the 1st
amplifier. Icom have used special customized high specification devices
to improve IMD and achieve better impedance characteristics. As a
result, the 3kHz roofing filter provides approximately 134dB of blocking
dynamic range and allows you to pull out a weak signal while blocking
strong adjacent signals.
* At 14.1MHz receive, with 5kHz separation of interference signal.
2nd image rejection mixer
The image rejection mixer for the 2nd stage rejects image spurious
through IF processing. In conjunction with the roofing filters,
rejection characteristics of more than 100 dB can be realized. The
result of the stable operation of the analogue image rejection mixer
makes it possible to design a simplified receiver circuit, and improve
the distortion-free performance of the receiver.
High stability OCXO unit
The frequency control of these circuits is done by the high stability
Oven Controlled Crystal Oscillator unit. This OCXO unit has �}0.05ppm
high stability on the basis of temperature. That means that within the
specified temperature range, the frequency will deviate only 5Hz out of
every 100 million Hz! This specification is equivalent to that
specialized measuring equipment. Also, a 10MHz reference frequency can
be the input/output for external equipment
7-inch wide colour TFT LCD
The large 7-inch (800 �~ 400 pixels) TFT colour display shows operating
frequencies various settings and operating conditions as well as
spectrum scope, S-meter and RTTY/PSK31 decoded messages. The S-meter
shows near analogue like needle swings that are smooth and accurate. In
addition to the 3 styles of digital meter, the IC-7700 has digital
multi-function bar graphic meters to show various conditions such as
Final PA temperature, PA voltage etc. Further more, the IC-7700 has a
VGA connector for an external monitor and an S-meter connector for an
external analogue S-meter.
USB ports on the front panel
Two USB ports on the front panel, allowing you to easily connect USB
type keyboard or USB memory stick to save transceiver settings, update
firmware, or transfer settings to other IC-7700's.
RTTY / PSK31 operation without PC connection
