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ANTENNA MATCHING PROCEDURE
THIS SECTION SHOULD BE STUDIED CARE-
FULLY BEFORE USING THE FC-700. WHILE
A
STRAIGHTFORWARD PROCEDURE, AN-
TENNA MATCHING WITH A COUPLER SUCH
AS
THE
FC-700
INVOLVES A
LOGICAL
PROGRESSION OF STEPS, AND FAMILIARITY
WITH THE TOTALITY OF THE FOLLOWING
SECTION WILL AVOID POSSIBLE DAMAGE TO
THE EQUIPMENT CAUSED BY INCORRECT
ADJUSTMENTS.
To summarize thé procédure that is followed in
using thé FC-700 antenna coupler to match a feed-
line to thé transmitter, thé following process takes
place:
1)
The proper inductance is chosen using thé
BAND selector.
2)
The LOAD and TUNE controls are adjusted
to secure a minimum SWR. Thèse two
controls should be adjusted one at a time,
so as to avoid confusion as to thé effect of
any particular adjustment. A typical pro-
cédure to follow would be to apply power,
adjust thé TUNE control for minimum SWR,
then adjust thé LOAD direction either to thé
right or left.
Once thé LOAD control has been changed,
thé TUNE control should again be adjusted
for minimum SWR; if this procédure improves
thé SWR, it should be continued by further
moving thé LOAD control in thé same direc-
tion, but if thé initial change in thé LOAD
control worsens thé SWR, move thé LOAD
control in thé opposite direction. It will be
clear to thé operator when thé LOAD control
is being adjusted in thé right direction.
Refer to Figure 1, where thé approximate positions
of thé BAND, LOAD, and TUNE controls are
shown for matching to a 50-ohm load. The internai
dummy load is used to preset thé controls for thé
operating frequency. The antenna may then be
selected, with final tuning taking only a few
seconds.
(1) Set up thé FT-77 or other transceiver for
normal opération. Set thé DUMMY/ANT
switch to DUMMY to sélect thé built-in
dummy load. Reduce thé drive control on thé
transceiver to thé minimum, and place thé
transmitter in thé "standby" condition for
thé moment.
(2)
Place thé B A N D , LOAD, und TUNE ton trois
in thé positions shown in Figure 1 for thé
frequency nearest that at which thé antenna
is to be matched. Set thé function switches
to thé FWD, SWR. and 150W positions. Set
thé SWR SETknob to thé 12 o'clock position.
(3)
Make preliminary matching adjustments with
as little transmitter power as possible. Place
thé FT-77 in thé "transmit" condition (CW
and press PTT), and slowly advance thé
drive until deflection of thé meter needle
on thé FC-700 is observed.
Adjust thé
SWR SET control to align thé meter needle
with thé SET marking on thé meter scale.
Now switch thé FWD/REV switch to REV
for accurate reading of thé SWR.
(4) Adjust thé TUNE control for minimum SWR.
If necessary, adjust thé SWR SET control
and/or transmitter drive to ensure proper
calibration (be certain to check thé SWR
meter sensitivity with thé FWD/REV switch
in thé FWD position, then switch back to
REV).
Once thé "dip" has been found using thé
TUNE control, move thé LOAD control a
small amount in either direction, left or right.
Adjust thé TUNE control for a "dip" again,
and if thé SWR is lowered, move thé LOAD
control slightly more in thé same direction as
before. Again "dip" thé TUNE control, and
continue this procédure until no further
improvement is noted. If thé initial direction
of adjustment of thé LOAD control makes
thé SWR higher, move thé control an equal
distance in thé opposite direction from thé
starting point, and "dip" thé TUNE control.
Remember to recheck thé calibration of thé
SWR meter to avoid misleading readings.
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