Yaesu FT-847 Operating Manual

Also see for FT-847: Technical supplement Technical supplement Technical supplement Modification

Contents

61FT-847 OPERATING MANUALOPERATIONANTENNA TUNER MEMORY SYSTEMfrequency a few kHz, then press the [TUNER] keyagain for ½ second, as slight changes in the reac-tance may allow a match to be obtained. Then goback to the original frequency and try again.3. Another technique which may allow matching insome situations is to add a few feet or meters ofcoaxial cable on the “antenna side” of the FC-20.This will change the impedance transformation tak-ing place in the coaxial cable, possibly moving theimpedance presented to the FC-20 into an accept-able range. Note that this is not changing the actualantenna SWR, but only the impedance “seen” bythe FC-20’s matching circuits.4. If your antenna system presents an SWR of lessthan 1.5:1, you may wish to turn off the antennatuner, as full transmitter power will be delivered tothe antenna system without intervention by the FC-20.5. If the impedance encountered by the FC-20 exceeds3:1, and the “HI SWR” icon is illuminated, the mi-croprocessor will not retain the tuning data for thatfrequency, as the FC-20 presumes that you willwant to adjust or repair your antenna system so asto correct the high SWR condition.ANTENNA TUNER (FC-20) OPERATIONThe FC-20, working in concert with the FT-847, canstore impedance matching data in its micro-computermemory, so as to provide instant adjustment as youtransmit in different areas of a particular band. A totalof 100 memories are provided: 11 of these are “gen-eral” memories apportioned one per band, while theremaining 89 are allocated for specific frequency datawithin the various bands, with the capability to resolvenew tuning data every 10 kHz. A few guidelines shouldbe noted regarding the FC-20’s memory system:1. Tuning data is stored when you make an active ef-fort to store it by pressing and holding in the[TUNER] key for ½ second. Although the tunerwill automatically activate itself if it encountersmore than 1.5:1 SWR, this memory will not bestored unless you have pressed the [TUNER] keyfor ½ second. This allows you to store your favor-ite operating frequency areas into tuner memorywithout tying up memory space with matching dataon seldom-used frequencies.2. If the FC-20 cannot resolve a satisfactory matchbecause the SWR is above 3:1 (2:1 on the 50 MHzband), the tuning process will stop, and no memorydata will be stored. However, you may wish to move