Hal Communications CWR6850, Instruction Manual

Page: 14 / 64

CHAPTER 3 PAGE 14
If all these indicators are as described, your CWR6850 is functioning properly; if not, re-check your
front panel switch settings.
Now, preset your receiver for the following conditions:
FREQUENCY: 14.075 to 14.100 MHz
ANTENNA: Antenna for above frequency range
MODE: LSB (lower sideband) *
PASSBAND TUNING: LSB
AGC: ON – SLOW
SELECTIVITY: 2 kHz – normal SSB voice bandwidth
RF GAIN: Maximum
AUDIO GAIN: Comfortable listening level – see following discussion
* Use RTTY on Drake TR7; LSB on all other transceivers
Turn up the volume control of the receiver for a comfortable listening level from the CWR6850 in-
ternal monitor speaker. Leave the receiver set for this volume and use the INPUT slide control for
further speaker volume adjustments.
If your receiver has an internal crystal calibrator, turn it on and tune the receiver to it so that you
get a 1 – 3 kHz audio beat note. If you do not have a crystal calibrator, tune the frequency until
you get a beat note on the carrier signal. There are two different types of tuning indicators you
may use when tuning RTTY signals on the CWR860:
1. The MARK and SPACE LEDs on the front panel.
2. A crossed-ellipse indication on an external X-Y oscilloscope (connected to the OSCILLO
- MARK and SPACE rear panel connectors).
We will experiment with the first technique at this time; the external scope can be tried at a later
time (see Chapter 5).
Tune your receiver frequency and notice that, as the beat note frequency changes, the MARK and
SPACE LEDs will alternately turn on as you tune through their filters. You will need to tune slowly
and carefully since the mark and space filters differ in frequency by only 850 Hz. Note that the
lower frequency audio tone (at 1275 Hz) turns on the MARK light; the higher frequency tone (2125
Hz) turns on the SPACE light. Therefore, a correctly tuned RTTY signal will be indicated by alter-
nate flickering of MARK and SPACE LEDs.
Next, turn-off the receiver calibrator (or tune away from the carrier) and select 170 shift (170
SHIFT button in). Tune the receiver while listening through the CWR6850 monitor speaker until
you find a moderately strong amateur RTTY signal (identified by the characteristic "deedle-deedle"
tones). With careful tuning you should be able to tune so that the MARK and SPACE light flicker al-
ternately. You should now see understandable text on the screen. If you don't, try the NORM / RE-
VERSE switch – if this corrects the reception, double check your receiver settings to be sure you
are really are receiving LSB and not USB. If this doesn't give you a good "print", try increasing the
CWR6850 speed, trying both NORM and REV polarities for each speed. If you still can't make
sense out of the display, try the ASCII code at 110 baud, either polarity. If all the combinations of
MODE, SPEED and NORM / REV fail, tune to another station, you have probably tuned-in an en-
crypted signal! Tune around the 20 meter amateur band and get used to tuning-in RTTY signals.
It's difficult at first, but becomes much easier with some practice.