[Icom] To buy a rig or two

[Adam Farson]

Hi John,

The IC-740 was a superb radio in its time. The hambands-only Icom IC-740
used a frequency-generation scheme similar to that of the Ten-Tec Omni
V/VI - a divided-down VHF PLL synthesiser for the 2nd L.O. Instead of a
crystal bank, though, the 1st L.O. was a single-loop PLL with a step size of
500 kHz (as I recall). This large step size held the phase-noise
contribution of the 1st L.O. to a negligible level. Both L.O. subsystems
were locked to a single master oscillator, thus ensuring the frequency
accuracy and stability were determined by the master oscillator.

The ARRL product review of the IC-740 (QST, September 1983, p. 39) indicated
that the IC-740 frequency generator was much quieter than any of the
conventional PLL implementations previously tested, and that the measured
dynamic range even exceeded that of some analogue VFO transceivers. Of
course, the compromise which had to be struck here was hambands-only
coverage - a fact which locked the IC-740 design out of non-amateur markets.

An excellent filter selection was available. (Inrad 455 kHz filters are also
"drop-in" for the 740). With 9 MHz and 455 kHz crystal filters fitted, the
IC-740 also offered PBT. More IC-740 information is available here:

http://www.qsl.net/icom/

http://www.qsl.net/ab4oj/icom/oldicom.html

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Icom FAQ site:
http://www.qsl.net/icom/