Icom IC-701

When an AFSK generator is used
PHONES AF
JACK
RTTY
DEMODULATOR
(TU)
uM 7
60mA or 20mA LOOP meen
LOOP CURRENT
POWER SUPPLY
MIC
CONNECTOR
5-5 OTHER OPERATIONS
5-5-1 VSWR READING .
The IC-701 has a built-in VSWR meter for checking antenna
matching in order to avoid problems caused by VSWR.
Set the METER Select switch to the Po position, the T/R
switch to Transmit, and Mode switch to the RTTY position.
Adjust the SWR SET control so that the meter needle
points to ““SET’’ on the meter scale. Set the SWR switch,
located under the access cover, to the SWR _ position.
(Before your unit is shipped, the SWR switch is fixed in
place in the SET position with a plastic screw. Remove
this screw before trying to make VSWR readings). With
the switch in the SWR position, SWR reading can be seen
on the meter. Although this unit is built to handle VSWR
of up to 2:1, it is recommended that the antenna(s) be
adjusted for the lowest possible VSWR. After taking the
reading, return the switch to the SET position. ALSO BE
SURE THAT THE ANTENNA IMPEDANCE IS 52 OHMS
OR THERE MAY NOT BE ANY OUTPUT. OTHERWISE
THERE WILL BE DAMAGE TO THE TRANSCEIVER.
The final transistors used in the 1C-701 are of good design
and are protected to a resonable extent by circuits
incorporated in the set. These devices can be expected to
have an indefinite lifetime since there are no cathodes to
burn out. Under some conditions, however, they can be
abused beyond tolerance and may have to be replaced.
When in doubt about antenna systems, use the lowest
power setting possible to achieve meaningful readings. Use
a good tuner or transmatch when necessary. Always use
caution and exercise judgement when testing RF power
generators.
5-5-2 AUTO DIMMER
For optimum visual comfort, the meter lamp and frequency
AFSK
GENERATOR
display LEDs are automatically dimmed and brightened
depending on the brightness or darkness of the surrounding
light by use of a built-in Dimmer Photosensor, located on
the right side of the frequency display on the front panel.
For the AUTO DIMMER to function properly, take care
that the dimmer photosensor is not covered by your hand
or other object.
The threshold for the functioning of the AUTO DIMMER
can be adjusted by turning the DIM GAIN Control, located
under the access cover. Rotating the control counter-
clockwise will lower the operation threshold of the circuit.
The circuit can be turned OFF by the DIM switch located
also under the access cover.
5-5-3 WWV RECEPTION
To receive WWV (or other standard frequency station), set
the BAND SELECT switch to the 14MHz band and the
MODE switch to the USB or LSB position. Tune to
15.000.0MHz on the frequency display. The WWYV signal
can be used for alignment of a frequency counter, marker
oscillator, or the frequency display.
5-5-4 SIMPLE FREQUENCY ALIGNMENT
A very accurate frequency counter is necessary to align the
frequency of the IC-701. However, the frequency can be
aligned simply by receiving the WWV signal.
1. Set the frequency display to 15.000.0MHz and be sure
that you are receiving the WWV signal.
2. Set the Mode Select switch to CW. A 900Hz beat can
be heard.
3. Short the KEY Jack on the rear panel so that the CW
sidetone also becomes audible.
4. Rotate the FREQUENCY SET Control, located under
the access cover, so that the two tones are of the same
pitch. If the tones are difficult to adjust because of a
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