Hal Communications CWR6850, Инструкция по эксплуатации

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CHAPTER 3 PAGE 18
sent CW but may also distort or garble copy of properly sent CW. When SPACE NARROW is se-
lected, the CWR6850 also may not track sudden changes in received CW WPM rates, particularly if
a decrease in speed of more than 12 % is encountered. Use the SPACE NARROW feature only if
run-together characters are suspected as the cause of distorted reception.
Similarly, it is a very common thing to insert longer than normal pauses between letters, especially
when using a hand key to send Morse. The computer interprets these pauses as spaces between
words and puts a space on the screen. When receiving by ear, we tend to group the letters re-
ceived into recognizable words, ignoring irregularities in spacing.
In these two cases in particular, the computer is a severe critic and "prints 'em as it hears 'em"! On
the other hand, the Morse decoding programs are very tolerant of weight variations and will usu-
ally correctly decipher a heavy "swing fist" (sometimes called a "Lake Erie swing"), This type of "in-
terface timing" problem will occur with all computer decoding of hand-sent Morse code, much as it
will on RTTY if improper or irregular timing is used.
You may notice that sometimes the Morse reception appears to stop or be "locked-up". This is usu-
ally caused by reception of a carrier for some period of time. The automatic speed tracking pro-
gram of the CWR6850 interprets the long carrier as very slow CW and adjust the speed tracking
system for very very slow Morse code. The CWR6850 will readjust the speed tracking back up to
the correct signal speed. You will now receive a few "T" and "E" characters as the speed readjusts.
Also, Morse code reception is particularly susceptible to interference when the transmitting sta-
tion's key is up (between dots or between letters and words). comparing RTTY and Morse techni-
ques for the moment, recall that the RTTY signal is sent by frequency shifting a signal (the RF sig-
nal for HF and audio tone for VHF AFSK), for either mark or space RTTY data conditions, there is a
definite signal transmitted. On Morse code, the transmitter carrier is turned on when the key is
down (mark), but when the key is up (space), there is no signal to be received; your receiver and
particularly the automatic Morse detection circuits are now "wide-open" to reception of noise, oth-
er signals etc. This is a basic disadvantage of the on-off A1 type emission we use for Morse versus
the F1 or F3 emission we use for RTTY. If we used F1, frequency shift keying, for Morse transmis-
sion (as do many commercial networks), automatic CW reception would be much improved. Here
again, when we copy CW by ear, we are adaptive and "tune-out" interference and noise in the
pauses between dots and dashes; the computer looks at all signals!
Therefore, it is not realistic to assume that the computer will do all the work of Morse reception for
you, especially when receiving less than perfect CW! On the other hand, if you tune to another
station using a keyboard or a professional CW operator (such as on the ship-to-shore frequencies),
the CWR6850 will display received Morse with close to RTTY-like perfection.
If your receiver has a narrow-bandwidth CW filter, you may now wish to try it for CW reception.
Tuning the signal will be a lot more critical, but you may improve the "copy" noticeably if interfer-
ence has been a problem. Conversely, the narrow filter may actually degrade the copy, especially if
the narrow filter "rings" on noise! The degree of problem caused by filter ringing varies with the fil-
ter, receiver and noise conditions, so you will want to experiment with your own equipment. Often,
the effects of noise, both with or without a narrow filter, can be minimized be reducing the RF gain
control until the AGS no longer controls the receiver gain, increasing the receiver volume control as
required to maintain copy. This technique, of course, makes the receiver system more active par-
ticipation on your part in adjustment of the RF gain control. Good Morse reception will require
some patience and practice until you "get the hang of it".