This page describes the modifications that were necessary to implement FM transmission and reception into the IC-720A from Icom. It is an older all-band transceiver with PLL that can be recognized by the noise of its step-switch relay when changing the amateur radio bands (klack-klack-klack...).
Originally, only SSB, CW, AM and RTTY (AFSK) were supported. Since AFSK transmission was implemented by a XTAL-oscillator with swichable capacitors and it seemed to be the least usable mode anyway, I decided to change it into FM....
You can view the modifications I did to the transceiver, as a how-to-build online guide.
Or you can download the LaTeX/Xfig sources (coming soon) to print it in a better quality.
This page was last modified 1999/07/19 by
DL4SDC.
It can be viewed with any browser.