K1EL K45 CW Modem Manual K45
K-45 User’s Manual - Rev A
6/6/2021
Page 31
CWR Adjustments
There are four adjustments that can be made to the CWR decoder’s signal path that can compensate for
poor decoding conditions. Gain, low pass filtering, noise floor thresholding, and inter-letter spacing can all be
adjusted to improve copy.
CWR Gain Adjustment
Signal gain is adjustable to compensate for low or high receiver level. The gain should be set to a point that
is high enough to provide sufficient signal level to run the CWR without causing overload on very strong
signals. Ten different gain levels are provided. A fast way to adjust CWR gain is to hold down the
CTL
key
and press the left and right arrow keys. New values of gain are flashed on the status line:
CG:n
where n is a
gain level between 0 and 9. There are ten gain settings. CWR gain can also be adjusted in Configuration
Menu #4:CWR Gain.
CWR Low Pass Filtering
There is a digital low pass filter in the CWR DSP processing path. This essentially controls how very short
impulses are processed. It can effectively heal elements that are broken up by very fast noise impulses. Ten
levels of low pass filtering are provided. A fast way to adjust the CWR filter is to hold down the
ALT
key and
press the left and right arrow keys. New values of filtering are flashed on the status line:
CF:n
where n is a
filter level between 0 and 9. Filtering can also be adjusted in Configuration Menu #R Filt.
CWR Noise Floor Threshold Adjustment
Although low pass filtering on the K45 CWR will help decode a noisy signal, a very high level of background
noise can degrade copy quality. Threshold adjustment can help with background noise by raising the signal
threshold so that the CWR will ignore any signal below the threshold. This can help greatly when copying a
station just above the noise level. Thresholding is adjusted by holding the ALT key down while pressing the
up and down arrows. The updated threshold level is flashed on the status line as
CT:n
where n will be the
threshold level setting. For best results, set the threshold just above the point where random band noise
triggers the letter decoding. Threshold can also be adjusted in Configuration Menu #4:CWR Thrsh.
CWR Inter-letter Spacing Allowance
Another challenge is trying to copy poor sending technique; letters that are run together, poorly constructed,
or varying widely in speed are not easy to copy by ear or machine. Adjusting the spacing allowance helps
compensate for incorrect spacing between dits and dahs which can cause letters to be run together or words
broken apart. There are ten settings which are adjusted by holding the CTL key down while pressing the up
and down arrows. The updated spacing adjustment is flashed on the status line as
CS+n
or
CS:-n
where n
will be the adjustment setting. Zero selects normal spacing. Selecting negative values tightens spacing to
address run together letters, for example the case when UR RST prints as URRST. Positive values pull
elements together, for example when an UR RST prints as U R R S T. Because this setting varies greatly
depending on conditions, it is not stored in EEPROM but defaults to zero on power up.
CWR Rx WPM Rate
The current received WPM rate is displayed on the left of status line. Speed is determined by the average
width of received dits. This means that it can be misled by Farnsworth formatted CW. For example, if you
copy W1AW code practice at 10 WPM, the K45 CWR will report a faster speed. Although ARRL code
practice is sent at 10 WPM the individual elements are sent at a faster speed.
CWR Rx Display
Morse decoded by the CWR is added to the receive text buffer and displayed in the RX display window.
Since this is only three-line display, it is often necessary to scroll back to “review the log”. The CWR always
runs in the background decoding and buffering incoming Morse. So even if the display is scrolled back many
lines, new incoming text is not missed. There are times when the CWR is not running:
1) When the K45 is transmitting
2) The CWR is powered down
3) RTTY mode is active
4) During practice
5) During WinKeyer mode