Icom has been the pioneer in the amateur radio industry for over 40 years, and has made dreams come true for hams all over the world. After releasing IC-X1, prototype of the IC-781, Icom released the IC-781 as a mass production model, which still remains an active model that is used worldwide. Even after 15 years, its performance and confidence in it remains highly rated. In September 2002, the IC-781 production was halted due to discontinuation of parts. However, this was not done without signs of distress from its long-time users. Meanwhile, opinions and requests from users regarding changes in the HF band specific environment and operating purposes, as well as expectations for a new product, have all been forwarded to Icom. With this in mind, Icom has decided to develop a HF transceiver that will truly be the ultimate in terms of performance, function, and quality without no comprise being made. This was to be achieved through combining accumulated RF expertise and the most advanced digital technology.
The performance of a receiver is ultimately determined by how well it picks up very weak signals, how it selects the intended signal from strong interference and noise, and if it can reproduce it as faithfully as possible. In terms of transmission, how clean a radio wave can be transmitted determines performance. Amateur radio manufacturers as well as operators worldwide have long been pursuing such qualities that determine this basic performance. Over the years, operability and functionality have greatly improved, and new functions have been added. However, the analog performance had not improved greatly from the standard level required in a radio. This project started with Icom reviewing the basic receiver and transmitter performance from the ground up.
Whenever discussing a transceiver's performance, the word 'distortion' always comes into play. It is needless to say that performance is influenced by distortion. It is an element that cannot be avoided unless perfectly linear semiconductors could be developed. Also, extremely high level signals that come in through the antenna or when handling high output, passive units also experience distortion. The IC-7800 development began with this distortion issue. Minute details of the circuits were reviewed, the best devices for each circuit were selected, and the latest technology was used to greatly improve each circuit's distortion characteristics.
In the RF component, by incorporating the image rejection mixer of the latest technology, the IC-7800 utilizes a double conversion super-heterodyne system, and a composition that has binary systems of all blocks from antenna input to audio output. It is like having 2 receiver units in the transceiver, and resulting in a very extravagant assembly. The band path filter and a pre-amp included mixer IF in the front end are designed so that each circuit emphasizes eliminating distortion-causing element. As a result, a third order intercept point +40dBm and an 110dB dynamic range that is good enough for professional use, has been created.
The 200W power output over the HF band and 50MHz bands with excellent IMD characteristics has been achieved through careful attention to signal level distortion all the way from the microphone to antenna output. A newly designed push-pull power MOS-FET amplifier has also been added, and the radio is run on high voltage.
All this basic RF performances is supported by four independent 32-bit floating point DSP integrated circuits. One for the transmitter, one for each receiver, and one for the spectrum scope. Each DSP unit controls the 1st IF stage, and in terms of reception, AGC loop management, IF filtering, noise reduction have improved signal selectivity and the dynamic range. In regards to transmission, each mode specific signal management greatly improves the quality of the radio wave. Also, at the top of the receiver, a digitally controlled automatic pre-selector is installed, which dramatically increases strong interfering signals. With such digital technology, and using the software that meet demands of various operating environment and modes, we are able to bring out superior analog performance. We can say that we have been able to achieve the exquisite balance between analog technology and digital technology.
Along with abundant functions, a large 7-inch wide color TFT LCD display which displays settings and operating conditions, an independent knob control for main band and sub band, and keys have been included in the transceiver. In this way, the basic operations as well as visual issues are well accounted for without affecting the operability of the transceiver.
The IC-7800 should be used forever with as much preference shown for the IC-781. The ultimate transceiver IC-7800 is a high spec radio that has realized the idealization of amateur radios, as well as remaining loyal to the basics. The IC-7800 is for DX'ers who pursue weak radio waves with ears wide open, and for contesters who seek to end in the top ranks. We know that IC-7800 is a status stating radio that can only offer but the maximum satisfaction to its users.