Frequency Calibration; Swr Checking - Icom IC-735 Instruction Manual

1 3 5 7 9 +20dB +60d8
RF 0 10 25 50
SWR 1 1
.
52 3
711 - 6
A very accurate frequency counter is necessary to accurately and
completely align the IC-735. However, a useful way of checking the
frequency readout is described below.
6 - 11 FREQUENCY CALIBRATION
WWV/WWVH RECEPTION
6 - 12 SWR CHECKING
1.
PUSH the METER SWITCH to the PO position
(OUT).
RF
POWER
METER
ALC
PO
2.
Slide rear panel METER SWITCH to "SET".
Po SET SWR
1 1 1 1 1 1
3.
Push the XMIT SWITCH to transmit position
(ON).
4. SET
5.
Set the rear panel METER SWITCH to SWR.
Po SET
SWR
111111H —
Radio station WWV/WWVH (or any other standard frequency station
such as CHU on 7.335MHz) may be used to check a frequency
counter, a marker oscillator or the frequency readout of the IC-735.
This is a method of using WWV/WWVH at 10MHz.
1. Tune the frequency to 9.999.0MHz (desired freq. — 1 kHz) and
select the USB mode. Listen for WWV/WWVH.
2. Turn ON the 25kHz MARKER SWITCH, S2 located on the PL
board by sliding it to the "MKR ON" position. The location of
S2 is shown on page 44.
3. Adjust the trimmer capacitor, C138 on the PL board for zero
beat between the marker signal and WWV/WWVH. The location
of C138 is shown on page 44. It is easiest to do this adjustment
when WWV/WWVH is transmitting a single audio tone.
4. Turn OFF the MARKER SWITCH on the PL board.
This method calibrates the reference oscillator, therefore it is not
necessary to calibrate the IC-735 on any other frequency.
The IC-735 has a built-in VSWR meter to check the voltage standing-
wave ratio of the antenna system, and avoid problems caused by a
mismatch between the transmitter and the antenna.
The following is the procedure to read the VSWR directly from the
front panel meter.
1. Push the METER SWITCH in the SWITCH PANEL to the PO
position (OUT).
2. Slide the METER SWITCH on the rear panel of the IC-735 to the
SET position as in the diagram.
3. Push the FM MODE SELECT SWITCH, and then push the XMIT
SWITCH to the transmit position (IN).
4. Adjust the RF POWER CONTROL in the SWITCH PANEL for a
full scale meter reading so the needle rests on "SET".
5. Slide the METER SWITCH on the rear panel to the SWR position.
Read the VSWR from the meter.
6. After taking the VSWR reading, return the METER SWITCH on
the rear panel to the Po position.
WARNING: Although the IC-735 is designed to handle a VSWR
of 1.5:1, try to reduce the VSWR as
much as
possible. If the impedance of the antenna system is
not close to 50 ohms, there may be little or no out-
put from the transceiver. This condition could
damage your IC-735.