Yaesu FT-847 Operating Manual page 63

A T M
NTENNA UNER
The FC-20, working in concert with the FT-847, can
store impedance matching data in its micro-computer
memory, so as to provide instant adjustment as you
transmit in different areas of a particular band. A total
of 100 memories are provided: 11 of these are "gen-
eral" memories apportioned one per band, while the
remaining 89 are allocated for specific frequency data
within the various bands, with the capability to resolve
new tuning data every 10 kHz. A few guidelines should
be 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 tuner
will automatically activate itself if it encounters
more than 1.5:1 SWR, this memory will not be
stored unless you have pressed the [TUNER] key
for ½ second. This allows you to store your favor-
ite operating frequency areas into tuner memory
without tying up memory space with matching data
on seldom-used frequencies.
2. If the FC-20 cannot resolve a satisfactory match
because the SWR is above 3:1 (2:1 on the 50 MHz
band), the tuning process will stop, and no memory
data will be stored. However, you may wish to move
FT-847 O
PERATING
A T
NTENNA UNER
S
EMORY YSTEM
M
ANUAL
( FC-20 ) O
PERATION
frequency a few kHz, then press the [TUNER] key
again for ½ second, as slight changes in the reac-
tance may allow a match to be obtained. Then go
back to the original frequency and try again.
3. Another technique which may allow matching in
some situations is to add a few feet or meters of
coaxial cable on the "antenna side" of the FC-20.
This will change the impedance transformation tak-
ing place in the coaxial cable, possibly moving the
impedance presented to the FC-20 into an accept-
able range. Note that this is not changing the actual
antenna SWR, but only the impedance "seen" by
the FC-20's matching circuits.
4. If your antenna system presents an SWR of less
than 1.5:1, you may wish to turn off the antenna
tuner, as full transmitter power will be delivered to
the antenna system without intervention by the FC-
20.
5. If the impedance encountered by the FC-20 exceeds
3:1, and the "HI SWR" icon is illuminated, the mi-
croprocessor will not retain the tuning data for that
frequency, as the FC-20 presumes that you will
want to adjust or repair your antenna system so as
to correct the high SWR condition.
OPERATION
61