KGKSDR build 40 released (CW TX)
- KGKSDR build 40 has been released to the website download area at:
This has a facility for cancelling the opposite image, and a fledgling
CW TX capability and I will try to describe the new features in this
post as the help file has not been updated yet ;-)
Under options > transceiver there are a couple of new items on the
hardware tab. On the ports panel, you can set the com port for the
four pins that connect the PC to the outside world.
* Morse key: Key in normally CTS.
* PTT in: DCD but can be also be CTS (not implemented yet, will be
used as PTT for SSB).
* Common high: DTR. This is a voltage source point to power morse key
and ptt button (more later).
* PTT to TX: RTS. This is the TX/RX line to control the Softrock.
Wiring up. RTS goes straight to the Softrock as described above. The
DTR line is set by the software to a positive voltage (measures +9V on
the port here). This can be connected via a 4.7K pullup resistors to
the morse key input and/or PTT input leaving them floating at 9V to
12V when the contacts are open. If you are using an external keyer it
should be fine with this arrangement.
From the options menu, select "Set TX manual cal point..." which will
bring up the calibration screen.
Hit the TX on box and you will start transmitting a continuous
carrier. Note that the status bar on the main screen goes dark red
when you are transmitting.
The idea with this screen is that you output a tone and the screen
will tell you where the image is likely to appear. Using a different
receiver, you monitor the image frequency. Using the S meter and your
ears, you play around with the amplitude and phase adjustments until
the image disappears in the mush.
Hit the 'save point' button and move onto a different frequency.
Repeat the process until you get bored (12-20 points is probably enough).
The frequency slider takes you close to the + and - Nyquist
frequencies and various frequencies in between.
The amplitude and phase controls are each in two parts. The left-hand
control moves the values up and down, and the right-hand control acts
as a zoom function allowing you to access finer resolutions.
Start off on coarse settings and spin the amplitude and phase looking
for a dip in the image. Repeat if required. Move the zoom controls
to the right by one click to get finer control and play around with
phase and amplitude again.
With a bit of practice you should be able to null the image quite
quickly. A bit of advice: don't bother chasing your tail by trying to
get -120dB image rejection. If you cough, or the line voltage changes
the image will jump back again and you will never achieve perfection.
You will get very frustrated, don't ask me how I know ;-)
There are a couple of tabs that show the amplitude and phase charts in
addition to the controls, and a clear all button if you want to start
Assuming some cal work has been done and you have wired up the serial
port as described earlier on, simply plug in the keyer or hand key and
off you go. There is no need to select TX, the software flips between
the two automatically.
There are a few rough edges, like the RX monitors the TX and not
everyone will like that. Also, the AGC gets pumped by the TX - this
can be fixed by temporarily suspending AGC while the transmitter is
on. I'll spend a week or two getting CW straight, and then do
something with the SSB side.
Have fun & 73,